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1
Sneed, William A. "Satellite Remote Sensing of Arctic Glacier-Climate Interactions." Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/SneedWA2007.pdf.
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Hodul, Matus. "Photogrammetric Bathymetry for the Canadian Arctic." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37553.
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This study proposes and demonstrates a through-water photogrammetry approach for Satellite Derived Bathymetry (SDB), which may be used to map nearshore bathymetry in the Canadian Arctic. A four step process is used: First, a standard photogrammetric extraction is performed on 2 m resolution WorldView stereo imagery, then apparent depths are calculated by referencing submerged points to the extracted elevation of the water level seen in the image. Due to the effects of refraction, these apparent depths are underestimates, and a refraction correction factor is applied to convert to actual depths. Finally, tidal stage at the time of image acquisition is used to bring depths to chart datum. A post processing step may be applied to remove erroneous depths caused by water surface objects such as boats, debris, or large waves. This was demonstrated in six study areas across Nunavut, Canada to test its robustness under a variety of environmental conditions, including different seafloor types, and under varying sea states. The six study sites were (with vertical accuracy given in Root Mean Square Error/and vertical bias, both in meters): eastern Coral Harbour (1.18/0.03), western Coral Harbour (0.78/-0.32), Cambridge Bay (1.16/0.08), Queen Maud Gulf (0.97/0.13), Arviat (1.02/0.13), and Frobisher Bay, where bathymetry extraction largely failed due to unfavourable sea surface conditions. These findings show that the proposed method has similar or better vertical accuracy as currently established SDB approaches; however, it has several benefits over the established methods which make it better suited for the Arctic. Namely, not requiring the precise atmospheric correction necessary for physics-based models, which is difficult at high latitudes; as well as being able to function in heterogeneous seafloor environments and not needing in-situ calibration data like the empirical spectral ratio approach, better suiting it to remote Arctic waters which often lack existing bathymetric survey data.
3
Bingham, A. W. "Monitoring Arctic glaciers and ice caps using Satellite Remote Sensing." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.596644.
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Routine monitoring of Arctic glaciers and ice caps is only possible using synthetic aperture radar (SAR). To make effective use of SAR, an algorithm to geocode SAR imagery is developed; the algorithm utilises a DEM to correct for terrain effects. Methods for collecting <I>in situ</I> data are also described; the data are then used to validate backscattering models. It is shown that during the summer melt season the physical optics model provides the best prediction of ERS-1 SAR backscatter from Arctic glaciers. High resolution satellite imagery is required to classify the surface facies on Arctic glaciers and ice caps. The potential of Landsat MSS and ERS-1 SAR for this application is explored. A Landsat TM image discriminates five distinct facies in cloud-free conditions, while a SAR image is unable to discriminate many surface facies. To improve the capability of SAR, backscatter values are normalised and dual-look images are used. Normalisation removes the dependency on incidence angle; this is achieved using the physical optics model. Images from an ascending and descending satellite pass are combined and it is demonstrated that up to five surface facies can be discriminated. It is estimated that the classification accuracy of a normalised, dual-look SAR image is about 65%, compared with 80% from a TM image; the SAR-derived ELA is within ± 5 m of the TM-derived ELA. A hybrid-classification scheme is applied to normalised, dual-look ERS-1 SAR imagery of Finsterwalderbreen and Austfonna, acquired at the end of a balance year. ELA measurements are used to calculate net mass balance and the potential of carrying out routine monitoring is assessed. The findings suggest that a combination of satellite reconnaissance and the direct glaciological method can provide a cost effective solution for routinely and systemically measuring the net mass balance of Arctic glaciers that are terminated by land and not highly deformed. However, the solution is presently not recommended for use on Arctic ice caps because of image requirements.
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Ehrlich, André, Eike Bierwirth, and Manfred Wendisch. "Airborne remote sensing of Arctic boundary-layer mixed-phase clouds." Universität Leipzig, 2010. https://ul.qucosa.de/id/qucosa%3A16357.
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This article gives an overview on the investigations on Artic boundary-layer mixed-phase clouds conducted within the Arctic Study of Tropospheric Aerosol, Clouds and Radiation (ASTAR) in spring 2007. In particular the horizontal and vertical disribution of ice crystals within the clouds was determined by three independent airborne instruments (lidar, in situ and solar radiation measurements). Spectral measurements of cloud top reflectivity have been utilized to retrieve information on the ice phase by analyzing the spectral pattern of the cloud top reflectance in the wavelength range dominated by liquid water and ice absorption (1400-1700 nm). A new algorithm to derive an ice index which distinguishes pure ice, liquid water, and mixed-phase clouds was developed. The horizontal distribution of the ice index, observed during ASTAR 2007, agrees with airborne lidar and in situ measurements showing patches of glaciated clouds at an air mass transition zone within the investigated mixed-phase cloud fields. Information on the vertical distribution of ice crystals in mixed-phase clouds was derived by comparing the measured cloud top reflectivity in the wavelength band 1400-1700 nm to radiative transfer simulations. To interpret the data, the vertical weighting of the measurements was calculated. In the investigated wavelength range the weightings differ according to the spectral absorption of ice and liquid water. From the observed spectral cloud reflectivity with low values in the ice absorption maximum (1400 nm) and higher values at the liquid water absorption maximum (1700 nm) it was concluded that ice crystals were present in the otherwise liquid dominated cloud top layer. Although in situ measurements (limited due to vertical resolution and detection limits) did confirm these findings only in certain limits, the retrieved vertical structure is in agreement with published ground based remote sensing measurements.
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Triplett, Colin Charles. "Rocket and lidar studies of waves and turbulence in the arctic middle atmosphere." Thesis, University of Alaska Fairbanks, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10147175.
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<p> This dissertation presents new studies of waves and turbulence in the Arctic middle atmosphere. The study has a primary focus on wintertime conditions when the large-scale circulation of the middle atmosphere is disrupted by the breaking of planetary waves associated with sudden stratospheric warming (SSW) events. We used ongoing Rayleigh lidar measurements of density and temperature to conduct a multi-year study of gravity waves in the upper stratosphere-lower mesosphere (USLM) over Poker Flat Research Range (PFRR) at Chatanika, Alaska. We analyzed the night-to-night gravity wave activity in terms of the wind structure and the ageostrophy. We find that the weak winds during disturbed conditions block the vertical propagation of gravity waves into the mesosphere. The gravity wave activity is correlated with the altitudes where the winds are weakest. During periods of weak winds we find little correlation with ageostrophy. However, during periods of stronger winds we find the USLM gravity wave activity is correlated with the ageostrophy in the upper troposphere indicating that ageostrophy in this region is a source of the gravity waves. Inter-annually we find the wintertime gravity wave activity is correlated with the level of disturbance of the middle atmosphere, being reduced in those winters with a higher level of disturbance and weaker winds. We used rocket-borne ion gauges to measure turbulence in the wintertime middle atmosphere while documenting the larger meteorological context from Rayleigh lidar and satellites. This investigation of turbulence was called the Mesosphere-Lower Thermosphere Turbulence Experiment (MTeX). During MTeX we found a highly disturbed atmosphere associated with an SSW where winds were weak and gravity wave activity was low. We found low levels of turbulence in the upper mesosphere. The turbulence was primarily found in regions of convective instability in the topside of mesospheric inversion layers (MILs). The strongest and most persist turbulence was found in a MIL that is associated with the breaking of a monochromatic gravity wave. These MTeX observations indicate that turbulence is generated by gravity wave breaking as opposed to gravity wave saturation. These MTeX findings of low levels of turbulence are consistent with recent model studies of vertical transport during SSWs and support the view that eddy transport is not a dominant transport mechanism during SSWs.</p>
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Kinda, Bazile. "Acoustic remote sensing of Arctic Sea Ice from long term soundscape measurements." Phd thesis, Université de Grenoble, 2013. http://tel.archives-ouvertes.fr/tel-00940393.
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La fonte rapide des glaces de l'Arctique dans le contexte actuel du réchauffement climatique est un sujet scientifique majeur de ces 30 dernières années. L'Arctique joue un rôle fondamental dans l'équilibre du climat et requiert une attention particulière. Les régions arctiques sont alors surveillées par des observations satellitaires et des mesures in-situ. L'impact climatique de la fonte totale de la glace arctique est encore mal connu. Des recherches sont donc nécessaires pour le suivi à long terme de l'Océan Arctique, en particulier la dynamique spatio-temporelle de la couverture de glace et ses conséquences sur les écosystèmes. La disparition de la banquise en Arctique sera progressivement accompagnée de l'installation d'activités industrielles saisonnières ou pérennes. Ceci a pour conséquences une modification des paysages acoustiques sousmarins de ces environnements jusqu'alors préservés des sources sonores anthropiques. La présente étude, portée sur les paysages acoustiques sous-marins des régions océaniques polaires du Canada, s'inscrit dans ce contexte sous deux axes. Le premier axe de notre étude concerne donc les conséquences directes de la disparition de la glace sur les paysages acoustiques sous-marins de l'Arctique et des mers subarctiques du Canada. Nous avons alors examiné le bruit ambiant, ses variations saisonnières ainsi ses pilotes environnementaux. Un algorithme dédié à l'estimation de cette composante du bruit océanique a été développé à cet effet, afin de constituer des séries temporelles longue durée. A travers des analyses statistiques, nous avons établi que les variables environnementaux responsables de la production du bruit de fond dépendent de l'état de la surface océanique et que pendant la période hivernale, ce bruit est piloté par les mêmes variables environnementales qui gouvernent la circulation océanique à grande échelle de l'Arctique. Le second axe abordé au cours de ce travail de thèse vise à évaluer le potentiel de l'acoustique passive comme moyen de monitorage de la dynamique spatio-temporelle de la banquise. Pour ce faire, nous avons identifié des événements acoustiques signant de phénomènes physiques sous la glace afin d'améliorer la compréhension de leur mécanisme de production. Nous avons ainsi pu lier divers transitoires acoustiques à des processus de déformation de la banquise.
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Kinda, Gnouregma Bazile. "Acoustic remote sensing of Arctic sea ice from long term soundscape measurements." Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENU032/document.
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La fonte rapide des glaces de l'Arctique dans le contexte actuel du réchauffement climatique est un sujet scientifique majeur de ces 30 dernières années. L'Arctique joue un rôle fondamental dans l'équilibre du climat et requiert une attention particulière. Les régions arctiques sont alors surveillées par des observations satellitaires et des mesures in-situ. L'impact climatique de la fonte totale de la glace arctique est encore spéculatif. Des recherches sont donc nécessaires pour le suivi à long terme de l'Océan Arctique, en particulier la dynamique spatio-temporelle de la couverture de glace et ses conséquences sur les écosystèmes. Notre travail s'inscrit dans ce contexte, et est porté sur le paysage sonore des régions polaires avant leur possible industrialisation qui accompagnera la fonte de la glace. Ainsi, nous avons d'abord examiné les conséquences de la disparition du couvert de glace sur les paysages sonores de ces régions. Nous avons alors étudié les variations saisonnières du bruit de fond et ses pilotes environnementaux. De ce fait, nous avons développé un algorithme d'estimation du bruit ambiant afin de pouvoir constituer des séries temporelles à partir des données acoustiques longue durée. Deuxièmement, nous avons étudié les transitoires générés par le comportement mécanique de la banquise en Arctique. Cette étude vise d'une part à comprendre le mécanisme de production de ces transitoires sous la glace, et d'autre part à évaluer leur potentiel comme moyen d'observation de la dynamique de la glace de mer<br>The Arctic sea ice melting, in the global warming context, has become a major scientific topic during the last 30 years. The Arctic Ocean plays a fundamental role in the global climate balance and requires a particular attention. The Arctic Regions are then monitored by satellite observations and in-situ measurements. The climatic impact of the total melting of the Arctic sea ice is not yet understood and researches are still needed for long term monitoring of Arctic Ocean, particularly the dynamics of the ice cover and its consequences on the ecosystems. Our work focused on the natural soundscapes of these Polar Regions prior to their possible industrialization. So, we first examined the impact of climate warming alone on polar soundscapes by studying the seasonal variability of ambient noise and its environmental drivers. We then developed an ambient noise estimation algorithm for automatic extraction of this noise component from long term measurements. In second, we examined the acoustic transients generated by the mechanical behavior of the ice cover at its maximum extent. This aims to better understanding of the physical processes involved in under-ice noise production and their potential use for sea ice monitoring
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Bondurant, Allen C. "Processes Controlling Thermokarst Lake Expansion Rates on the Arctic Coastal Plain of Northern Alaska." Thesis, University of Alaska Fairbanks, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10615802.
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<p> Thermokarst lakes are a dominant factor of landscape scale processes and permafrost dynamics in the otherwise continuous permafrost region of the Arctic Coastal Plain (ACP) of northern Alaska. Lakes cover greater than 20% of the landscape on the ACP and drained lake basins cover an additional 50 to 60% of the landscape. The formation, expansion, drainage, and reformation of thermokarst lakes has been described by some researchers as part of a natural cycle, the thaw lake cycle, that has reworked the ACP landscape during the course of the Holocene. Yet the factors and processes controlling contemporary thermokarst lake expansion remain poorly described. This thesis focuses on the factors controlling variation in extant thermokarst lake expansion rates in three ACP regions that vary with respect to landscape history, ground-ice content, and lake characteristics (i.e. size and depth). Through the use of historical aerial imagery, satellite imagery, and field-based data collection, this study identifies the controlling factors at multiple spatial and temporal scales to better understand the processes relating to thermokarst lake expansion. Comparison of 35 lakes across the ACP shows regional differences in expansion rate related to permafrost ice content ranging from an average expansion rate of 0.62 m/yr on the Younger Outer Coastal Plain where ice content is highest to 0.16 m/yr on the Inner Coastal Plain where ice content is lowest. Within each region, lakes vary in their expansion rates due to factors such as lake size, lake depth, and winter ice regime. On an individual level, lakes vary due to shoreline characteristics such as local bathymetry and bluff height. Predicting how thermokarst lakes will behave locally and on a landscape scale is increasingly important for managing habitat and water resources and informing models of land-climate interactions in the Arctic.</p><p>
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Isleifson, Dustin. "Simulation and measurement techniques for microwave remote sensing of sea ice." IEEE, 2010. http://hdl.handle.net/1993/4812.
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This dissertation presents new research into the study of simulation and measurement
techniques for microwave remote sensing of sea ice. We have embarked on a major
study of the microwave propagation and scattering properties of sea ice in an attempt
to link the physics of the sea ice medium to experimentally obtained concomitant
scatterometer measurements.
During our fieldwork, we studied the polarimetric backscattering response of sea
ice, focusing on newly-formed sea ice under a large assortment of surface coverage.
Polarimetric backscattering results and physical data for 40 stations during the fall
freeze-up of 2003, 2006, and 2007 are presented. Analysis of the co-polarization
correlation coefficient showed its sensitivity to sea ice thickness and surface coverage
and resulted in a statistically significant separation of ice thickness into two regimes:
ice less than 6 cm thick and ice greater than 8 cm thick. A case study quantified the
backscatter of snow-infiltrated frost fl
owers on new sea ice, showing that the presence
of the frost
flowers enhanced the backscatter by more than 6 dB.
In our simulation work, an efficient method for simulating scattering from objects
in multi-layered media was incorporated into a scattered-field formulation of the FVTD
method. A total-field 1D-FDTD solution to the plane-wave propagation through
multi-layered meda was used as a source. The method was validated for a TE-polarized
incident-field through comparisons with other numerical techniques involving examples
of scattering from canonically-shaped objects.
Methods for homogenization of inhomogeneous media were developed and validated
using well-known dielectric mixture models. A Monte Carlo Method for simulating
scattering from statistically rough surfaces was developed and was validated through
favorable comparison with the SPM method for rough surface scattering.
Finally, we presented a new Monte Carlo Method for simulating sea ice remote
sensing that utilized the framework of the FVTD method for scattering simulations.
The modeling process was driven by actual physical measurements of sea ice, wherein
dielectric and physics-based modeling techniques were employed. The method was
demonstrated through a series of case studies where the scattering from newly-formed
sea ice was simulated using a TE-polarized incident- eld. Good agreement between
experimental scatterometer measurements and simulated results was obtained for
co-polarized returns, whereas cross-polarized results indicated that more depolarizing
features must be taken into account.
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Sheard, John Daniel. "Acoustic wave propagation in ice covered oceans." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319827.
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Jones, Lucas Alan. "Satellite Microwave Remote Sensing of Boreal-Arctic Land Surface State and Meteorology from AMSR-E." The University of Montana, 2008. http://etd.lib.umt.edu/theses/available/etd-12192007-163830/.
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High latitude regions are undergoing significant climate-related change and represent an integral component of the Earths climate system. Near-surface vapor pressure deficit, soil temperature, and soil moisture are essential state variables for monitoring high latitude climate and estimating the response of terrestrial ecosystems to climate change. Methods are developed and evaluated to retrieve surface soil temperature, daily maximum/minimum air temperature, and land surface wetness information from the EOS Advanced Microwave Scanning Radiometer (AMSR-E) on the Aqua satellite for eight Boreal forest and Arctic tundra biophysical monitoring sites across Alaska and northern Canada. Daily vapor pressure deficit is determined by employing AMSR-E daily maximum/minimum air temperature retrievals. The seasonal pattern of microwave emission and relative accuracy of the estimated land surface state are influenced strongly by landscape properties including the presence of open water, vegetation type and seasonal phenology, snow cover and freeze-thaw transitions. Daily maximum/minimum air temperature is retrieved with RMSEs of 2.88 K and 2.31 K, respectively. Soil temperature is retrieved with RMSE of 3.1 K. Vapor pressure deficit (VPD) is retrieved to within 427.9 Pa using thermal information from AMSR-E. AMSR-E thermal information imparted 27% of the overall error in VPD estimation with the remaining error attributable to underlying algorithm assumptions. Land surface wetness information derived from AMSR-E corresponded with soil moisture observations and simple soil moisture models at locations with tundra, grassland, and mixed -forest/cropland land covers (r = 0.49 to r = 0.76). AMSR-E 6.9 GHz land surface wetness showed little correspondence to soil moisture observation or model estimates at locations with > 20% open water and > 5 m2 m-2 Leaf Area Index, despite efforts to remove the impact of open water and vegetation biomass. Additional information on open water fraction and vegetation phenology derived from AMSR-E 6.9 GHz corresponds well with independent satellite observations from MODIS, Sea-Winds, and JERS-1. The techniques and interpretations of high-latitude terrestrial brightness temperature signatures presented in this investigation will likely prove useful for future passive microwave missions and ecosystem modeling.
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Shipigina, Ekaterina. "Remote sensing methods for environmental monitoring of human impact on sub-Arctic ecosystems in Europe." Thesis, University of Cambridge, 2013. https://www.repository.cam.ac.uk/handle/1810/268066.
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The role and scale of human impact on the global environment is a question of special importance to the scientific community and the world as a whole. This impact has dramatically increased since the beginning of industrialisation, yet its understanding remains patchy. The sub-Arctic plays a central role in forming the global environment due to the vast territory of boreal forest and tundra. Severe climatic conditions make its ecosystems highly sensitive to any natural and human disturbances. In this context, the dynamics of boreal vegetation, and of the forest/tundra interface (the treeline), is the most representative indicator of environmental changes in the sub-Arctic. For some time now, monitoring land cover and vegetation changes using remote sensing techniques have been a powerful method for studying human impact on environment from landscape to global scales. It is particularly efficient when applied to the sub-Arctic ecosystems. Remote sensing gives access to accurate and specific information about distant and hard-to-reach areas across forest and tundra. Despite all the e orts, there is a lack of uniformity in studying human impact, a shortage of mapping of impact over large territories and a lack of understanding of the relation between human activity and environmental response. This dissertation develops a systematic approach to monitoring land cover and vegetation changes under human impact over northern Fennoscandia. The study area extends north and south of the treeline and covers around 400,000km2 reaching from Finnmark in Norway, through Norrbotten in Sweden, Lapland in Finland up to the Murmansk region in Russia. This is the most populated and industrially developed region of the whole sub-Arctic and, therefore, suffering most from human impact. This dissertation identifies industrial atmospheric pollution, reindeer herding, forest logging, forest fires and infrastructure development as the primary types of human impact close to the treeline. For each type characteristic hotspots are identified and human impact is analysed in the context of physical environment as well as cultural, economical and political development of the area. This dissertation presents an automated workflow enabling large-scale land cover mapping in northern Fennoscandia with high throughput. It starts with automated image pre-processing using image metadata and ends with automated mapping of classification results. A single classifier for multispectral Landsat data is trained on extensive field data collected across the whole region. Open source tools are used extensively to set up the processing scripts enabling rapid and reproducible analysis. Using the developed advanced remote sensing methodology land cover maps are constructed for all identified hotspots and types of human impact. Changes in vegetation are analysed using three or four historical land cover maps for each hotspot. More than 35 Landsat TM and ETM+ images covering the period from the 1980s until 2011 are processed in an automated manner. A strong correlation between the level of impact and the scale of vegetation change is confirmed and analysed. The structure and dynamics of the local treeline and the quality of environment are analysed and assessed in the context of changing levels of impact at each hotspot and regionally.
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Juhls, Bennet [Verfasser]. "Land-Ocean Interactions in Arctic Coastal Waters: Ocean Colour Remote Sensing and Current Carbon Fluxes to the Arctic Ocean / Bennet Juhls." Berlin : Freie Universität Berlin, 2021. http://d-nb.info/1225741637/34.
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Swan, Aaron M. "Multi-year Arctic Sea Ice Classification Using QuikSCAT." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/2762.
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Long term trends in Arctic sea ice are of particular interest with regard to global temperature, climate change, and industry. This thesis uses microwave scatterometer data from QuikSCAT and radiometer data to analyze intra- and interannual trends in first-year and multi-year Arctic sea ice. It develops a sea ice type classification method. The backscatter of first-year and multi-year sea ice are clearly identifiable and are observed to vary seasonally. Using an average of the annual backscatter trends obtained from QuikSCAT, a classification of multi-year ice is obtained which is dependent on the day of the year (DOY). Validation of the classification method is done using regional ice charts from the Canadian Ice Service. Differences in ice classification are found to be less than 6% during the winters of 06-07, 07-08, and the end of 2008. Anomalies in the distribution of sea ice backscatter from year to year suggest a reduction in multi-year ice cover between 2003 and 2009 and an approximately equivalent increase in first-year ice cover.
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Nyland, Kelsey Elizabeth. "Climate- and Human- Induced Land Cover Change and its Effects on the Permafrost System in the Lower Yenisei River of the Russian Arctic." Thesis, The George Washington University, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1589678.
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<p> Climate warming is occurring at an unprecedented rate in the Arctic, seriously impacting sensitive environments, and triggering land cover change. These changes are compounded by localized human influences. This work classifies land cover change for the Lower Yenisei River, identifies those changes that were climate- and anthropogenic- induced, and discusses the implications for the underlying permafrost system. This is accomplished using a modified version of the “Landsat dense time stacking” methodology for three time periods spanning 29 years that are representative of Russian socio-economic transitions during the mid- to late-1980s (1985-1987), the early 2000s (2000-2002), and the contemporary 2010s (2012-2014). The classified area includes three cities indicative of different post-Soviet socio-economic situations, including continued population and infrastructure decline (Igarka), a relatively stable community (Dudinka), and a community receiving local reinvestment (Norilsk). The land cover classification, in tandem with regional climate reanalysis data, enabled climate- and anthropogenic- induced changes to be identified, characterized, and quantified. Climatic changes within the natural environments have produced a steady greening effect throughout the study area, as well as an increase in large lake abundance, indicative of permafrost degradation. Pollution, in close proximity to heavy industrial activity, caused a secondary plant succession process. The results of this work provide both map products that can be applied to future research in this region, as well as insights into the impacts of the warming climate and human presence on sensitive Arctic environments.</p>
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Zhang, Ke. "Study on regional responses of pan-arctic terrestrial ecosystems to recent climate variability using satellite remote sensing." Diss., [Missoula, Mont.] : The University of Montana, 2009. http://etd.lib.umt.edu/theses/available/etd-06042009-125041.
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Preusser, Andreas [Verfasser], and Günther [Akademischer Betreuer] Heinemann. "Multi-sensor remote sensing of long-term circumpolar polynya characteristics in the Arctic / Andreas Preusser ; Betreuer: Günther Heinemann." Trier : Universität Trier, 2017. http://d-nb.info/1197807586/34.
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Gupta, Mukesh. "On the estimation of physical roughness of a marginal sea ice zone using remote sensing." John Wiley and Sons, Ltd, 2013. http://hdl.handle.net/1993/23836.
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This thesis provides insight into techniques for the detection and classification of various marginal ice zone roughnesses in the southern Beaufort Sea using in situ and satellite-based microwave remote sensing. A proposed model of surface roughness shows the dependence of circular coherence, a discriminator of roughness, on the roughness and dielectrics. A relationship between ice slopes in azimuth and range direction is derived. Microwave brightness temperature of open water is significantly correlated with wave height but not with the wind speed, having the strongest correlations for the H-polarization at both 37 and 89 GHz. A modified formula for the relationship between non-dimensional form of energy and wave age at wind speeds 0−10 m/s is obtained. The brightness temperature (April−June) of sea ice at H-polarization of 89 GHz is found to decrease with increasing roughness, and is attributed to the dominant contributions from rapidly varying thermodynamic properties of snow-covered sea ice.
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Zhan, Shengan. "Spatio-Temporal Analysis of Gyres in Oriented Lakes on the Arctic Coastal Plain of Northern Alaska Based on Remotely Sensed Images." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1427982971.
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Smeda, Braden William. "Area and Volume Changes of Adams Icefield from 1948 to 2019, Axel Heiberg Island, Nunavut, Canada." Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/41602.
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There has been a marked increase in melt season length over the past two decades on glaciers and ice caps within Canada’s Queen Elizabeth Islands (QEI). Prior to the year ~2000 land ice was in a state of slightly negative mass balance (-11 +/- 11.5 Gt yr⁻¹ over 1958-1995), but recent GRACE measurements suggest that mass losses averaged -33 +/- 5 Gt yr⁻¹ between 2003-2015. These losses have primarily been attributed to meltwater runoff, making the QEI one of the largest recent contributors to sea level rise outside of the ice sheets. Despite these losses, there is a lack of information concerning how a warming climate is affecting small (<1 km²) ice bodies, which are considered sensitive indicators of change due to their short response time.
In this study, historical and contemporary aerial photographs, high resolution optical satellite imagery, and ground penetrating radar (GPR) surveys are used to determine area, thickness, mass and volume changes of Adams Icefield within Expedition Fiord, Axel Heiberg Island, Nunavut, over the past seven decades (1948/59-2019). Area changes are determined from a comparison of air photos acquired in 1948/59 with satellite images acquired since 1979. Contemporary (2001, 2012, 2019) digital elevation models (DEMs) were either collected or created from stereo satellite images, and via aerial photo surveys using Structure from Motion photogrammetry. DEM of Difference maps calculated from these DEMs provide volume and mass changes. Results illustrate a steady reduction in glacier area, thickness, and volume prior to the year ~2000, followed by a rapid increase in losses over the past two decades. As a result, Adams Icefield is now rapidly declining and is likely to completely disappear early in the twenty-second century.
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King, Tyler V. "Quantifying Dominant Heat Fluxes in an Arctic Alaskan River with Mechanistic River Temperature Modeling." DigitalCommons@USU, 2018. https://digitalcommons.usu.edu/etd/7224.
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Temperatures strongly affect physical, chemical, and biological processes in rivers and streams. The processes that influence river temperatures are known across most geographic regions, but the relative importance varies significantly. Little is known about what controls water temperature Arctic rivers, limiting our ability to understand the impacts of climate change. This dissertation addresses this knowledge gap by incorporating field measurements with river temperature modeling to estimate the relative importance of key factors that affect Arctic river temperatures. Results indicate that shortwave radiation (e.g., sunlight) and net longwave radiation are significant throughout an Arctic watershed in all flow conditions. In areas where the river is smaller, however, exchange of water with the riverbed and inputs of water from the landscape become significant under low-flow and high-flow conditions, respectively. Additional field observations and modeling were used to quantify the water and heat exchanges between the river and the riverbed. These heat exchanges were found to cool the river and reduce the daily range of temperatures. To better estimate the flow of water from the landscape to the river, a new method for estimating river flow was developed using high-resolution aerial imagery. This method allows us to estimate river flow without depending on field measurements, and presents a potential solution to barriers in performing river temperature modeling in other parts of the Arctic.
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Lindell, David Brian. "Arctic Sea Ice Classification and Soil Moisture Estimation Using Microwave Sensors." BYU ScholarsArchive, 2016. https://scholarsarchive.byu.edu/etd/6153.
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Spaceborne microwave sensors are capable of estimating various properties of many geophysical phenomena, including the age and extent of Arctic sea ice and the relative soil moisture over land. The measurement and classification of such geophysical phenomena are used to refine climate models, localize and predict drought, and better understand the water cycle. Data from the active Ku-band scatterometers, the Quick Scatterometer (QuikSCAT), and the Oceansat-2 Scatterometer (OSCAT), are here used to classify areas of first-year and multiyear Arctic sea ice using a temporally adaptive threshold on reported radar backscatter values. The result is a 15-year data record of daily ice classification images. An additional ice age data record is produced using the C-band Advanced Scatterometer (ASCAT) and the Special Sensor Microwave Imager Sounder (SSMIS) with an alternate classification methodology based on Bayesian decision theory. The ASCAT/SSMIS classification methodology results in a record which is generally consistent with the QuikSCAT and OSCAT classifications, which conclude in 2014. With multiple ASCAT and SSMIS sensors still operational, the ASCAT/SSMIS ice classifications can continue to be produced into the future. In addition to ice classification, ASCAT is used to estimate the relative surface soil moisture at high-resolution (4.45 — 4.45 km per pixel). The soil moisture estimates are obtained using enhanced resolution image reconstruction techniques and an altered version of the Water Retrieval Package (WARP) algorithm. The high-resolution soil moisture estimates are shown to agree well with the existing lower resolution WARP products while also revealing finer details.
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Darlington, Eleanor F. "Meltwater delivery from the tidewater glacier Kronebreen to Kongsfjorden, Svalbard : insights from in-situ and remote-sensing analyses of sediment plumes." Thesis, Loughborough University, 2015. https://dspace.lboro.ac.uk/2134/19399.
Full textAbstract:
Tidewater glaciers form a significant drainage catchment of glacierised areas, directly transporting meltwater from the terrestrial to the marine environment. Surface melt of glaciers in the Arctic is increasing in response to warmer atmospheric temperatures, whilst tidewater glaciers are also exposed to warmer ocean temperatures, stimulating submarine melt. Increased freshwater discharge not only freshens fjord waters, but also plays a key role in glacimarine sedimentary processes, transporting sediment to glacial fjords. Despite this, the temporal evolution of meltwater production, storage and release from tidewater glacier systems at seasonal and interannual time scales is poorly understood. This leaves large uncertainties in the predictions for future sea level rise, ocean circulation and the impacts on the marine ecosystem. This study focuses on Kronebreen, a tidewater glacier which flows into the head of Kongsfjorden, north west Svalbard. Surface melt produces freshwater runoff, which is discharged from the grounding line as a buoyant, sediment laden plume, which spreads laterally across the surface water. This supraglacial melt is the dominant freshwater source, contributing an order of magnitude more freshwater to Kongsfjorden, than direct submarine melting of the ice face. Calibration of MODIS band 1 satellite imagery with in situ measurements of Total Suspended Solids and spectral reflectance, provides a method to quantify meltwater and sediment discharge. Plume extent has been determined for each cloud free day, from June to September, 2002 - 2013. Analysis of plume extent with atmospheric temperature and modeled surface runoff, gives a source to sea insight to meltwater production, storage and discharge. The extent of the plume changes in response to meltwater; larger plumes form when discharge increases. These results reveal that meltwater discharge into Kongsfjorden lags atmospheric temperature, the primary driver of meltwater production, by over a week during June and July. This is reduced to only 1 - 2 days in August and September, indicating a decline in meltwater storage as the ablation season progresses, and the development of more efficient glacial drainage. Sediment plumes respond to meltwater production, making them a valuable tool for quantifying meltwater discharge from a tidewater glacier. Insights to glacier hydrology can also be obtained when surface processes are also considered. This furthers the understanding of tidewater glacier hydrology, which is valuable for improving the accuracy of sea level rise predictions.
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Komarov, Alexander. "New methods for detecting dynamic and thermodynamic characteristics of sea ice from radar remote sensing." Institute of Electrical and Electronics Engineers, 2014. http://hdl.handle.net/1993/30225.
Full textAbstract:
This dissertation presents new methods for detecting dynamic and thermodynamic characteristics of Arctic sea ice using radar remote sensing.
A new technique for sea ice motion detection from sequential satellite synthetic aperture radar (SAR) images was developed and thoroughly validated. The accuracy of the system is 0.43 km obtained from a comparison between SAR-derived ice motion vectors and in-situ sea ice beacon trajectories. For the first time, we evaluated ice motion tracking results derived from co-polarization (HH) and cross-polarization (HV) channels of RADARSAT-2 ScanSAR imagery and formulated a condition where the HV channel is more reliable than the HH channel for ice motion tracking. Sea ice motion is substantially controlled by surface winds. Two new models for ocean surface wind speed retrieval from C-band SAR data have been developed and validated based on a large body of statistics on buoy observations collocated and coincided with RADARSAT-1 and -2 ScanSAR images. The proposed models without wind direction input demonstrated a better accuracy than conventionally used algorithms. As a combination of the developed methods we designed a wind speed-ice motion product which can be a useful tool for studying sea ice dynamics processes in the marginal ice zone.
To effectively asses the thermodynamic properties of sea ice advanced tools for modeling electromagnetic (EM) wave scattering from rough natural surfaces are required. In this dissertation we present a new analytical formulation for EM wave scattering from rough boundaries interfacing inhomogeneous media based on the first-order approximation of the small perturbation method. Available solutions in the literature represent special cases of our general solution. The developed scattering theory was applied to experimental data collected at three stations (with different snow thicknesses) in the Beaufort Sea from the research icebreaker Amundsen during the Circumpolar Flaw Lead system study. Good agreement between the model and experimental data were observed for all three case studies. Both model and experimental radar backscatter coefficients were considerably higher for thin snow cover (4 cm) compared to the thick snow cover case (16 cm). Our findings suggest that, winter snow thickness retrieval may be possible from radar observations under particular scattering conditions.
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Hoffmann, Anne. "Comparative aerosol studies based on multi-wavelength Raman LIDAR at Ny-Ålesund, Spitsbergen." Phd thesis, Universität Potsdam, 2011. http://opus.kobv.de/ubp/volltexte/2011/5242/.
Full textAbstract:
The Arctic is a particularly sensitive area with respect to climate change due to the high surface albedo of snow and ice and the extreme radiative conditions. Clouds and aerosols as parts of the Arctic atmosphere play an important role in the radiation budget, which is, as yet, poorly quantified and understood. The LIDAR (Light Detection And Ranging) measurements presented in this PhD thesis contribute with continuous altitude resolved aerosol profiles to the understanding of occurrence and characteristics of aerosol layers above Ny-Ålesund, Spitsbergen. The attention was turned to the analysis of periods with high aerosol load. As the Arctic spring troposphere exhibits maximum aerosol optical depths (AODs) each year, March and April of both the years 2007 and 2009 were analyzed. Furthermore, stratospheric aerosol layers of volcanic origin were analyzed for several months, subsequently to the eruptions of the Kasatochi and Sarychev volcanoes in summer 2008 and 2009, respectively.
The Koldewey Aerosol Raman LIDAR (KARL) is an instrument for the active remote sensing of atmospheric parameters using pulsed laser radiation. It is operated at the AWIPEV research base and was fundamentally upgraded within the framework of this PhD project. It is now equipped with a new telescope mirror and new detection optics, which facilitate atmospheric profiling from 450m above sea level up to the mid-stratosphere. KARL provides highly resolved profiles of the scattering characteristics of aerosol and cloud particles (backscattering, extinction and depolarization) as well as water vapor profiles within the lower troposphere. Combination of KARL data with data from other instruments on site, namely radiosondes, sun photometer, Micro Pulse LIDAR, and tethersonde system,
resulted in a comprehensive data set of scattering phenomena in the Arctic atmosphere.
The two spring periods March and April 2007 and 2009 were at first analyzed based on meteorological parameters, like local temperature and relative humidity profiles as well as large scale pressure patterns and air mass origin regions. Here, it was not possible to find a clear correlation between enhanced AOD and air mass origin. However, in a comparison of two cloud free periods in March 2007 and April 2009, large AOD values in 2009 coincided with air mass transport through the central Arctic. This suggests the occurrence of aerosol transformation processes during the aerosol transport to Ny-Ålesund. Measurements on 4 April 2009 revealed maximum AOD values of up to 0.12 and aerosol size distributions changing with altitude. This and other performed case studies suggest the differentiation between three aerosol event types and their origin: Vertically limited aerosol layers in dry air, highly variable hygroscopic boundary layer aerosols and enhanced aerosol load across wide portions of the troposphere. For the spring period 2007, the available KARL data were statistically analyzed using a characterization scheme, which is based on optical characteristics of the scattering particles. The scheme was validated using several case studies.
Volcanic eruptions in the northern hemisphere in August 2008 and June 2009 arose the opportunity to analyze volcanic aerosol layers within the stratosphere. The rate of stratospheric AOD change was similar within both years with maximum values above 0.1 about three to five weeks after the respective eruption. In both years, the stratospheric AOD persisted at higher rates than usual until the measurements were stopped in late September due to technical reasons. In 2008, up to three aerosol layers were detected, the layer structure in 2009 was characterized by up to six distinct and thin layers which smeared out to one broad layer after about two months. The lowermost aerosol layer was continuously detected at the tropopause altitude. Three case studies were performed, all revealed rather large indices of refraction of m = (1.53–1.55) - 0.02i, suggesting the presence of an absorbing carbonaceous component. The particle radius, derived with inversion calculations, was also similar in both years with values ranging from 0.16 to 0.19 μm. However, in 2009, a second mode in the size distribution was detected at about 0.5 μm.
The long term measurements with the Koldewey Aerosol Raman LIDAR in Ny-Ålesund
provide the opportunity to study Arctic aerosols in the troposphere and the stratosphere not only in case studies but on longer time scales. In this PhD thesis, both, tropospheric aerosols in the Arctic spring and stratospheric aerosols following volcanic eruptions have been described qualitatively and quantitatively. Case studies and comparative studies with data of other instruments on site allowed for the analysis of microphysical aerosol characteristics and their temporal evolution.<br>Die Arktis ist ein bezüglich Klimaveränderungen besonders sensitives Gebiet, d.h. die globale Erwärmung wirkt sich aufgrund der saisonal hochvariablen Strahlungsbedingungen und der Bodenalbedo dort verstärkt aus.Wolken und Aerosole als Bestandteile der arktischen Atmosphäre spielen dabei eine besondere Rolle im Strahlungsgleichgewicht. Die vorliegende Promotionsarbeit leistet mit Hilfe von LIDAR-Messungen (Light Detection and Ranging) einen Beitrag zum Verständnis von Vorkommen und Eigenschaften von Aerosolschichten über Ny-Ålesund, Spitzbergen. Besonderes Augenmerk liegt dabei auf der Analyse von Zeiträumen mit erhöhter Aerosolbelastung. Es wurde zum einen die arktische Troposphäre zweier Frühjahre (März und April der Jahre 2007 und 2009) untersucht, da im Frühjahr die Aerosol-optische Dicke (AOD) in der Arktis Maximalwerte erreicht. Zum anderen wurden stratosphärische Aerosolschichten vulkanischen Ursprungs analysiert, die in den Sommern 2008 und 2009 nach Ausbrüchen der Kasatochi und Sarychev Vulkane jeweils für mehrere Monate in der unteren Stratosphäre messbar waren.
Das an der AWIPEV Forschungsstation betriebene Koldewey Aerosol Raman LIDAR
(KARL), ein Instrument zur optischen Fernerkundung atmosphärischer Parameter mittels gepulster Laserstrahlung, wurde im Rahmen der Promotion grundlegend überarbeitet und mit einem neuen Teleskop sowie neuen Detektoroptiken versehen. Dies ermöglicht die Profilerfassung ab 450m über dem Meeresspiegel bis in die mittlere Stratosphäre. KARL liefert hochaufgelöste Messungen der Streueigenschaften von Aerosol- undWolkenteilchen (Rückstreuung, Extinktion und Depolarisation) sowieWasserdampfprofile in der unteren Troposphäre. Durch die Kombination von KARL Messungen mit Daten anderer Messgeräte an der AWIPEV Forschungsstation wie Radiosonden, Sonnenphotometer, Micro Pulse LIDAR und Fesselsonden wurde ein umfassender Datenbestand von Streuphänomenen in der arktischen Atmosphäre geschaffen.
Die beiden genannten Frühjahreszeiträume März und April 2007 und 2009 wurden zunächst anhand meteorologischer Parameter, wie lokaler Temperatur- und Feuchteprofile sowie großskaliger Druckmuster und Luftmassenquellgebiete analysiert. Dabei konnte kein eindeutiger Zusammenhang zwischen Quellgebieten und erhöhter AOD festgestellt werden. In einem Vergleich zweier wolkenfreier Perioden im März 2007 und April 2009 war jedoch die höhere Aerosolbelastung in 2009 mit dem Transport von Luftmassen durch die innere Arktis verbunden. Aufgrund der begrenzten Lebensdauer von Aerosolen lässt das entweder Aerosol-Entstehungsprozesse in der Zentralarktis oder Transformationsprozesse während des Transportes nach Ny-Ålesund vermuten. Für Messungen am 4. April 2009 mit Maximalwerten der AOD von bis zu 0.12 konnte die Größe der Aerosolteilchen in verschiedenen Höhen mit Hilfe von Inversionsrechnungen abgeschätzt werden. Diese und andere betrachtete Fallstudien legen eine Unterscheidung von Aerosolereignissen in drei Kategorien nahe, die sich in ihrer Entstehung deutlich unterscheiden: Vertikal begrenzte Aeosolschichten in trockener Luft, zeitlich hochvariable feuchte Aerosolschichten in der planetaren Grenzschicht sowie eine erhöhte Aerosolbelastung über große Teile der Troposphäre. Für das sehr klare Frühjahr 2007 wurden die vorhandenen KARL-Daten mit Hilfe eines Klassifikationsschemas, das auf den optischen Eigenschaften der streuenden Teilchen beruht, statistisch ausgewertet. Das verwendete Schema wurde mit Hilfe von verschiedenen Fallstudien validiert und ermöglicht bei Anwendung auf größere Datenbestände eine aussagekräftige Analyse von jährlichen Schwankungen der Aerosol- und Wolkenvorkommen über Ny-Ålesund.
Die Ausbrüche zweier Vulkane in der nördlichen Hemisphäre im August 2008 und im
Juni 2009 erlaubten die Analyse vulkanischer Aerosolschichten in der Stratosphäre. Die zeitliche Entwicklung der stratosphärischen AOD verlief in beiden Jahren ähnlich mit Maximalwerten von über 0.1 etwa drei bis fünfWochen nach dem jeweiligen Ausbruch. In beiden Jahren wurden bis zum technisch bedingten Abbruch der Messungen jeweils Ende September erhöhte stratosphärische AOD Werte gemessen. Die niedrigste Aerosolschicht konnte jeweils direkt an der Tropopause detektiert werden. Im Jahr 2008 wurden bis zu drei Schichten detektiert, die Struktur 2009 war durch bis zu sechs schmale Schichten gekennzeichnet, die nach etwa zwei Monaten zu einer breiten Schicht verschmierten. Drei Fallstudien zu mikrophysikalischen Aerosoleigenschaften wurden durchgeführt. Dabei wurden für beide Jahre sehr große Brechungsindices von m=(1.53–1.55) - 0.02i ermittelt, die auf eine absorbierende Kohlenstoffkomponente der Vulkanaerosole hinweisen. Der errechnete Teilchenradius war ebenfalls in beiden Jahren vergleichbar mit Werten zwischen 0.16 und 0.19 μm. 2009 wurde zusätzlich ein zweites Maximum der Größenverteilung bei ca. 0.5μm gefunden. Die Langzeitmessungen mit dem Koldewey Aerosol Raman LIDAR KARL in Ny-Ålesund schaffen die Möglichkeit, arktische Aerosole in Troposphäre und Stratosphäre nicht nur in Fallstudien, sondern auch über längere Zeiträume hinweg zu analysieren. Im Rahmen dieser Promotionsarbeit konnten sowohl Aerosolvorkommen in der arktischen Troposphäre im Frühjahr als auch eine vulkanisch bedingte erhöhte Aerosolbelastung in der Stratosphäre qualitativ und quantitativ beschrieben werden. Fallstudien und die Kombination mit Daten anderer Messgeräte ermöglichten Analysen mikrophysikalischer Aerosolparameter und deren Entwicklungsprozesse.
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Holman, Kiyomi. "Testing Approaches and Sensors for Satellite-Derived Bathymetry in Nunavut." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/41402.
Full textAbstract:
Nearshore bathymetry in the Canadian Arctic is poorly surveyed, but is vital knowledge for coastal communities that rely on marine transportation for resources and development. Nautical charts currently available are often outdated and surveying by traditional methods is both time consuming and expensive. Satellite-derived bathymetry (SDB) offers a significantly cheaper and faster option to provide information on nearshore bathymetry. The two most common approaches to SDB are empirical and physics-based. The empirical approach is simple and typically does well when calibrated with high-quality in-situ data, whereas the physics-based approach is more difficult to implement and requires precise atmospheric correction. This project tests the practical use of five methods within the empirical and physics-based approaches to SDB, using Landsat 8 and Sentinel-2 satellite imagery, at seven sites across Nunavut. Methods tested include: the Ratio-Transform, Multiband, and Random Forest Regression methods (empirical) and radiative transfer modeling (physics-based) using two atmospheric correction models: ACOLITE and Deep Water Correction. All methods typically use geolocated water depth data for validation, as well as calibration for the empirical methods. Spectral reflectance for model inputs were collected in Cambridge Bay, NU. Water depth data were acquired from the Canadian Hydrographic Service. All processing was conducted within the framework of plugins developed for the open-source GIS software, QGIS. Results from the empirical methods were typically poor due to poor calibration data, though Random Forest Regression performed well when good calibration data were available. Due to poor quality validation data, error for the physics-based results cannot be adequately quantified in most places. Additionally, atmospheric correction remains a challenge for the physics-based methods. Overall, results indicate that where large, high-quality calibration datasets are available, Random Forest Regression performs best of all methods tested, with little bias and low mean absolute error in water less than 10 m deep. As such datasets are rare in the Arctic, the physics-based method is often the only option for SDB and is an excellent qualitative tool for informing communities of shallow bathymetry features and assessing navigation risk.
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Hanesiak, John Michael. "Development of a one-dimensional electro-thermophysical model of the snow sea-ice system, arctic climate processes and microwave remote sensing applications." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ62637.pdf.
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König, Marcel [Verfasser], Natascha [Akademischer Betreuer] Oppelt, and Peter [Gutachter] Gege. "Mapping Melt Pond Bathymetry on Arctic Sea Ice by Means of Optical Remote Sensing / Marcel König ; Gutachter: Peter Gege ; Betreuer: Natascha Oppelt." Kiel : Universitätsbibliothek Kiel, 2021. http://d-nb.info/1234451379/34.
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Gydemo, Östbom Viktor. "Lake water chemistry and the changing arctic environment : Topographic or climatic control?" Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-155903.
Full textAbstract:
The arctic is expected to be one of the regions most affected by ongoing climate change, with relative changes in air temperatures significantly higher than the global mean. Lakes are recognized for their potential role in the global climate system and as ecosystems of importance for local societies. As such, there is a scientific interest regarding how arctic lakes and their geochemistry will respond to climatic changes. Lakes around Kangerlussuaq (66.99 N, 51.07 W), south-west Greenland, are known for their unique geochemical composition, including oligosaline lakes, of which some are enriched in colourless dissolved organic carbon (DOC). The origin of this DOC and the importance of local catchment properties for the general water chemistry is currently being debated. This thesis aimed at: i) exploring the extent and effect of catchment morphology on lake-water chemistry in the Kangerlussuaq area; ii) determine the predominant origin of DOC, aquatic or terrestrial. I used a remote-sensing approach based on satellite imagery and digital elevation model (DEM) in deciding landscape influence on water chemistry (pH, alkalinity, conductivity, base cations, sulphate, nitrogen and absorbance). To trace the origin of the organic sources behind DOC lake water and sediments, I used a hydrogen isotope tracing method. The remote sensing approach revealed that morphological characteristics serving as proxies for lake water residence time and hydrologic connectivity (e.g. lake altitude difference and absence of outlets) explained up to 77% of the variations in lake water chemistry. The hydrogen isotopic signature of the DOC indicated a predominantly autochthonous origin, i.e. 59 to 78% was estimated to originate from algae. I conclude that lake water chemistry of the lakes in the study area is primarily controlled by the precipitation : evaporation balance, enhanced by static catchment characteristics regulating water age. Thus, the examined lake water chemical properties are likely to remain across future climatic scenarios, providing the current precipitation : evaporation balance prevails.
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Nasonova, Sasha. "Estimating Arctic sea ice melt pond fraction and assessing ice type separability during advanced melt." Thesis, Remote Sensing, 2017. https://dspace.library.uvic.ca//handle/1828/9313.
Full textAbstract:
Arctic sea ice is rapidly declining in extent, thickness, volume and age, with the majority of the decline in extent observed at the end of the melt season. Advanced melt is a thermodynamic regime and is characterized by the formation of melt ponds on the sea ice surface, which have a lower surface albedo (0.2-0.4) than the surrounding ice (0.5-0.7) allowing more shortwave radiation to enter the system. The loss of multiyear ice (MYI) may have a profound impact on the energy balance of the system because melt ponds on first-year ice (FYI) comprise up to 70% of the ice surface during advanced melt, compared to 40% on MYI. Despite the importance of advanced melt to the ocean-sea ice-atmosphere system, advanced melt and the extent to which winter conditions influence it remain poorly understood due to the highly dynamic nature of melt pond formation and evolution, and a lack of reliable observations during this time. In order to establish quantitative links between winter and subsequent advanced melt conditions, and assess the effects of scale and choice of aggregation features on the relationships, three data aggregation approaches at varied spatial scales were used to compare high resolution satellite GeoEye-1 optical images of melt pond covered sea ice to winter airborne laser scanner surface roughness and electromagnetic induction sea ice thickness measurements. The findings indicate that winter sea ice thickness has a strong association with melt pond fraction (fp) for FYI and MYI. FYI winter surface roughness is correlated with fp, whereas for MYI no association with fp was found. Satellite-borne synthetic aperture radar (SAR) data are heavily relied upon for sea ice observation; however, during advanced melt the reliability of observations is reduced. In preparation for the upcoming launch of the RADARSAT Constellation Mission (RCM), the Kolmogorov-Smirnov (KS) statistical test was used to assess the ability of simulated RCM parameters and grey level co-occurrence matrix (GLCM) derived texture features to discriminate between major ice types during winter and advanced melt, with a focus on advanced melt. RCM parameters with highest discrimination ability in conjunction with optimal GLCM texture features were used as input parameters for Support Vector Machine (SVM) supervised classifications. The results indicate that steep incidence angle RCM parameters show promise for distinguishing between FYI and MYI during advanced melt with an overall classification accuracy of 77.06%. The addition of GLCM texture parameters improved accuracy to 85.91%. This thesis provides valuable contributions to the growing body of literature on fp parameterization and SAR ice type discrimination during advanced melt.<br>Graduate<br>2019-03-21
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Siriwardana, Chandawimal H. "CHARACTERIZATION OF PALEOCLIMATE AND MARINE PROCESSES ASSOCIATED WITH HOLOCENE SEDIMENTATION ON THE CHUKCHI MARGIN, ARCTIC OCEAN." Kent State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=kent1406718279.
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Choi, Sungyeon. "Investigation of tropospheric bro using space-based total column bro measurements." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/43682.
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We derive tropospheric column BrO during the ARCTAS and ARCPAC field campaigns in spring 2008 using retrievals of total column BrO from the satellite UV nadir sensors OMI and GOME-2 using a radiative transfer model and stratospheric column BrO from a photochemical simulation. We conduct a comprehensive comparison of satellite-derived tropospheric BrO column to aircraft in-situ observations of BrO and related species. The aircraft profiles reveal that tropospheric BrO, when present during April 2008, was distributed over a broad range of altitudes rather than being confined to the planetary boundary layer (PBL). Perturbations to the total column resulting from tropospheric BrO are the same magnitude as perturbations due to longitudinal variations in the stratospheric component, so proper accounting of the stratospheric signal is essential for accurate determination of satellite-derived tropospheric BrO. We find reasonably good agreement between satellite-derived tropospheric BrO and columns found using aircraft in-situ BrO profiles, particularly when satellite radiances were obtained over bright surfaces (albedo >0.7), for solar zenith angle <80 degree and clear sky conditions. The rapid activation of BrO due to surface processes (the bromine explosion) is apparent in both the OMI and GOME-2 based tropospheric columns. The wide orbital swath of OMI allows examination of the evolution of tropospheric BrO on about hourly time intervals near the pole. Low surface pressure, strong wind, and high PBL height are associated with an observed BrO activation event, supporting the notion of bromine activation by high winds over snow. We also provide monthly climatological maps of free tropospheric BrO volume mixing ratio (VMR) derived using the so-called cloud slicing technique. In this approach, the derived slope of the total column BrO versus cloud pressure is proportional to free tropospheric BrO VMR. Estimated BrO VMR shows a minimum in the tropics and greater values at higher latitudes in both hemispheres. High tropospheric BrO VMR at high latitudes in spring could be influenced by near-surface bromine activation.
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HURD, JOHN K. JR. "A GIS MODEL TO ESTIMATE SNOW DEPTH USING DIFFERENTIAL GPS AND HIGH-RESOLUTION DIGITAL ELEVATION DATA." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1177640172.
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Buschmann, Matthias [Verfasser], Justus [Akademischer Betreuer] Notholt, Justus [Gutachter] Notholt, and John P. [Gutachter] Burrows. "Ground-based remote sensing of carbon dioxide and methane in the Arctic using Fourier-transform infrared spectrometry / Matthias Buschmann ; Gutachter: Justus Notholt, John P. Burrows ; Betreuer: Justus Notholt." Bremen : Staats- und Universitätsbibliothek Bremen, 2017. http://d-nb.info/1160670544/34.
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Morgenstern, Anne. "Thermokarst and thermal erosion : degradation of Siberian ice-rich permafrost." Phd thesis, Universität Potsdam, 2012. http://opus.kobv.de/ubp/volltexte/2012/6207/.
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Current climate warming is affecting arctic regions at a faster rate than the rest of the world. This has profound effects on permafrost that underlies most of the arctic land area. Permafrost thawing can lead to the liberation of considerable amounts of greenhouse gases as well as to significant changes in the geomorphology, hydrology, and ecology of the corresponding landscapes, which may in turn act as a positive feedback to the climate system. Vast areas of the east Siberian lowlands, which are underlain by permafrost of the Yedoma-type Ice Complex, are particularly sensitive to climate warming because of the high ice content of these permafrost deposits.
Thermokarst and thermal erosion are two major types of permafrost degradation in periglacial landscapes. The associated landforms are prominent indicators of climate-induced environmental variations on the regional scale. Thermokarst lakes and basins (alasses) as well as thermo-erosional valleys are widely distributed in the coastal lowlands adjacent to the Laptev Sea. This thesis investigates the spatial distribution and morphometric properties of these degradational features to reconstruct their evolutionary conditions during the Holocene and to deduce information on the potential impact of future permafrost degradation under the projected climate warming. The methodological approach is a combination of remote sensing, geoinformation, and field investigations, which integrates analyses on local to regional spatial scales.
Thermokarst and thermal erosion have affected the study region to a great extent. In the Ice Complex area of the Lena River Delta, thermokarst basins cover a much larger area than do present thermokarst lakes on Yedoma uplands (20.0 and 2.2 %, respectively), which indicates that the conditions for large-area thermokarst development were more suitable in the past. This is supported by the reconstruction of the development of an individual alas in the Lena River Delta, which reveals a prolonged phase of high thermokarst activity since the Pleistocene/Holocene transition that created a large and deep basin. After the drainage of the primary thermokarst lake during the mid-Holocene, permafrost aggradation and degradation have occurred in parallel and in shorter alternating stages within the alas, resulting in a complex thermokarst landscape. Though more dynamic than during the first phase, late Holocene thermokarst activity in the alas was not capable of degrading large portions of Pleistocene Ice Complex deposits and substantially altering the Yedoma relief. Further thermokarst development in existing alasses is restricted to thin layers of Holocene ice-rich alas sediments, because the Ice Complex deposits underneath the large primary thermokarst lakes have thawed completely and the underlying deposits are ice-poor fluvial sands. Thermokarst processes on undisturbed Yedoma uplands have the highest impact on the alteration of Ice Complex deposits, but will be limited to smaller areal extents in the future because of the reduced availability of large undisturbed upland surfaces with poor drainage. On Kurungnakh Island in the central Lena River Delta, the area of Yedoma uplands available for future thermokarst development amounts to only 33.7 %. The increasing proximity of newly developing thermokarst lakes on Yedoma uplands to existing degradational features and other topographic lows decreases the possibility for thermokarst lakes to reach large sizes before drainage occurs.
Drainage of thermokarst lakes due to thermal erosion is common in the study region, but thermo-erosional valleys also provide water to thermokarst lakes and alasses. Besides these direct hydrological interactions between thermokarst and thermal erosion on the local scale, an interdependence between both processes exists on the regional scale. A regional analysis of extensive networks of thermo-erosional valleys in three lowland regions of the Laptev Sea with a total study area of 5,800 km² found that these features are more common in areas with higher slopes and relief gradients, whereas thermokarst development is more pronounced in flat lowlands with lower relief gradients. The combined results of this thesis highlight the need for comprehensive analyses of both, thermokarst and thermal erosion, in order to assess past and future impacts and feedbacks of the degradation of ice-rich permafrost on hydrology and climate of a certain region.<br>Die gegenwärtige Klimaerwärmung wirkt sich auf arktische Regionen stärker aus als auf andere Gebiete der Erde. Das hat weitreichende Konsequenzen für Permafrost, der weite Teile der terrestrischen Arktis unterlagert. Das Tauen von Permafrost kann zur Freisetzung erheblicher Mengen an Treibhausgasen sowie zu gravierenden Änderungen in der Geomorphologie, Hydrologie und Ökologie betroffener Landschaften führen, was wiederum als positive Rückkopplung auf das Klimasystem wirken kann. Ausgedehnte Gebiete der ostsibirischen Tiefländer, die mit Permafrost des Yedoma Eiskomplex unterlagert sind, gelten aufgrund des hohen Eisgehalts dieser Permafrostablagerungen als besonders empfindlich gegenüber Klimaerwärmungen.
Thermokarst und Thermoerosion sind zwei Hauptformen der Permafrostdegradation in periglazialen Landschaften. Die zugehörigen Landschaftsformen sind auf der regionalen Skala bedeutende Indikatoren klimainduzierter Umweltvariationen. Thermokarstseen und senken (Alasse) sowie Thermoerosionstäler sind in den Küstentiefländern der Laptewsee weit verbreitet. Die vorliegende Dissertation untersucht die räumliche Verbreitung und die morphometrischen Eigenschaften dieser Degradationsformen mit dem Ziel, ihre Entwicklungsbedingungen während des Holozäns zu rekonstruieren und Hinweise auf potenzielle Auswirkungen zukünftiger Permafrostdegradation im Zuge der erwarteten Klimaerwärmung abzuleiten. Der methodische Ansatz ist eine Kombination aus Fernerkundungs-, Geoinformations- und Geländeuntersuchungen, die Analysen auf lokalen bis regionalen räumlichen Skalen integriert.
Thermokarst und Thermoerosion haben die Untersuchungsregion tiefgreifend geprägt. Im Eiskomplexgebiet des Lena-Deltas nehmen Thermokarstsenken eine weitaus größere Fläche ein als Thermokarstseen auf Yedoma-Hochflächen (20,0 bzw. 2,2 %), was darauf hin deutet, dass die Bedingungen für die Entwicklung von großflächigem Thermokarst in der Vergangenheit wesentlich günstiger waren als heute. Die Rekonstruktion der Entwicklung eines einzelnen Alas im Lena-Delta belegt eine andauernde Phase hoher Thermokarstaktivität seit dem Übergang vom Pleistozän zum Holozän, die zur Entstehung einer großen und tiefen Senke führte. Nach der Drainage des primären Thermokarstsees im mittleren Holozän erfolgten Permafrostaggradation und degradation parallel und in kürzeren abwechselnden Etappen innerhalb des Alas und führten zu einer komplexen Thermokarstlandschaft. Trotzdem die spätholozäne Thermokarstentwicklung im Alas dynamischer ablief als die erste Entwicklungsphase, resultierte sie nicht in der Degradation großer Teile pleistozäner Eiskomplexablagerungen und einer wesentlichen Veränderung des Yedoma-Reliefs. Weitere Thermokarstentwicklung in bestehenden Alassen ist begrenzt auf geringmächtige Lagen holozäner eisreicher Alas-Sedimente, da die Eiskomplexablagerungen unter den großen primären Thermokarstseen vollständig getaut waren und die unterlagernden Sedimente aus eisarmen, fluvialen Sanden bestehen. Thermokarstprozesse auf ungestörten Yedoma-Hochflächen wirken am stärksten verändernd auf Eiskomplexablagerungen, werden aber in Zukunft auf geringere Ausmaße begrenzt sein, da die Verfügbarkeit großer ungestörter, schwach drainierter Yedoma-Hochflächen abnimmt. Auf der Insel Kurungnakh im zentralen Lena-Delta beträgt der für zukünftige Thermokarstentwicklung verfügbare Anteil an Yedoma-Hochflächen nur 33,7 %. Die zunehmende Nähe von sich entwickelnden Thermokarstseen auf Yedoma-Hochflächen zu bestehenden Degradationsstrukturen und anderen negativen Reliefformen verringert die Möglichkeit der Thermokarstseen, große Ausmaße zu erreichen bevor sie drainieren.
Die Drainage von Thermokarstseen durch Thermoerosion ist in der Untersuchungsregion weit verbreitet, aber Thermoerosionstäler versorgen Thermokarstseen und –senken auch mit Wasser. Neben diesen direkten hydrologischen Wechselwirkungen zwischen Thermokarst und Thermoerosion auf der lokalen Ebene existiert auch eine Interdependenz zwischen beiden Prozessen auf der regionalen Ebene. Eine regionale Analyse weitreichender Netze von Thermoerosionstälern in drei Tieflandgebieten der Laptewsee mit einer Fläche von insgesamt 5800 km² zeigte, dass diese Formen häufiger in Gebieten mit höheren Geländeneigungen und Reliefgradienten auftreten, während Thermokarstentwicklung stärker in flachen Tiefländern mit geringeren Reliefgradienten ausgeprägt ist. Die kombinierten Ergebnisse dieser Dissertation zeigen die Notwendigkeit von umfassenden Analysen beider Prozesse und Landschaftsformen, Thermokarst und Thermoerosion, im Hinblick auf die Abschätzung vergangener und zukünftiger Auswirkungen der Degradation eisreichen Permafrosts auf Hydrologie und Klima der betrachteten Region und deren Rückkopplungen.
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Buchhorn, Marcel. "Ground-based hyperspectral and spectro-directional reflectance characterization of Arctic tundra vegetation communities : field spectroscopy and field spectro-goniometry of Siberian and Alaskan tundra in preparation of the EnMAP satellite mission." Phd thesis, Universität Potsdam, 2013. http://opus.kobv.de/ubp/volltexte/2014/7018/.
Full textAbstract:
The Arctic tundra, covering approx. 5.5 % of the Earth’s land surface, is one of the last ecosystems remaining closest to its untouched condition. Remote sensing is able to provide information at regular time intervals and large spatial scales on the structure and function of Arctic ecosystems. But almost all natural surfaces reveal individual anisotropic reflectance behaviors, which can be described by the bidirectional reflectance distribution function (BRDF). This effect can cause significant changes in the measured surface reflectance depending on solar illumination and sensor viewing geometries.
The aim of this thesis is the hyperspectral and spectro-directional reflectance characterization of important Arctic tundra vegetation communities at representative Siberian and Alaskan tundra sites as basis for the extraction of vegetation parameters, and the normalization of BRDF effects in off-nadir and multi-temporal remote sensing data. Moreover, in preparation for the upcoming German EnMAP (Environmental Mapping and Analysis Program) satellite mission, the understanding of BRDF effects in Arctic tundra is essential for the retrieval of high quality, consistent and therefore comparable datasets. The research in this doctoral thesis is based on field spectroscopic and field spectro-goniometric investigations of representative Siberian and Alaskan measurement grids.
The first objective of this thesis was the development of a lightweight, transportable, and easily managed field spectro-goniometer system which nevertheless provides reliable spectro-directional data. I developed the Manual Transportable Instrument platform for ground-based Spectro-directional observations (ManTIS).
The outcome of the field spectro-radiometrical measurements at the Low Arctic study sites along important environmental gradients (regional climate, soil pH, toposequence, and soil moisture) show that the different plant communities can be distinguished by their nadir-view reflectance spectra. The results especially reveal separation possibilities between the different tundra vegetation communities in the visible (VIS) blue and red wavelength regions. Additionally, the near-infrared (NIR) shoulder and NIR reflectance plateau, despite their relatively low values due to the low structure of tundra vegetation, are still valuable information sources and can separate communities according to their biomass and vegetation structure. In general, all different tundra plant communities show: (i) low maximum NIR reflectance; (ii) a weakly or nonexistent visible green reflectance peak in the VIS spectrum; (iii) a narrow “red-edge” region between the red and NIR wavelength regions; and (iv) no distinct NIR reflectance plateau.
These common nadir-view reflectance characteristics are essential for the understanding of the variability of BRDF effects in Arctic tundra. None of the analyzed tundra communities showed an even closely isotropic reflectance behavior. In general, tundra vegetation communities: (i) usually show the highest BRDF effects in the solar principal plane; (ii) usually show the reflectance maximum in the backward viewing directions, and the reflectance minimum in the nadir to forward viewing directions; (iii) usually have a higher degree of reflectance anisotropy in the VIS wavelength region than in the NIR wavelength region; and (iv) show a more bowl-shaped reflectance distribution in longer wavelength bands (>700 nm). The results of the analysis of the influence of high sun zenith angles on the reflectance anisotropy show that with increasing sun zenith angles, the reflectance anisotropy changes to azimuthally symmetrical, bowl-shaped reflectance distributions with the lowest reflectance values in the nadir view position.
The spectro-directional analyses also show that remote sensing products such as the NDVI or relative absorption depth products are strongly influenced by BRDF effects, and that the anisotropic characteristics of the remote sensing products can significantly differ from the observed BRDF effects in the original reflectance data. But the results further show that the NDVI can minimize view angle effects relative to the contrary spectro-directional effects in the red and NIR bands. For the researched tundra plant communities, the overall difference of the off-nadir NDVI values compared to the nadir value increases with increasing sensor viewing angles, but on average never exceeds 10 %.
In conclusion, this study shows that changes in the illumination-target-viewing geometry directly lead to an altering of the reflectance spectra of Arctic tundra communities according to their object-specific BRDFs. Since the different tundra communities show only small, but nonetheless significant differences in the surface reflectance, it is important to include spectro-directional reflectance characteristics in the algorithm development for remote sensing products.<br>Die arktische Tundra ist mit circa 5,5 % der Landoberfläche eines der letzten großen verbliebenen fast unberührten Ökosysteme unserer Erde. Nur die Fernerkundung ist in der Lage, benötigte Informationen über Struktur und Zustand dieses Ökosystems großräumig und in regelmäßigen Zeitabständen zur Verfügung zu stellen. Aber fast alle natürlichen Oberflächen zeigen individuelle anisotrope Reflexionsverhaltensweisen, welche durch die bidirektionale Reflektanzverteilungsfunktion (englisch: BRDF) beschrieben werden können. Dieser Effekt kann zu erheblichen Veränderungen im gemessenen Reflexionsgrad der Oberfläche in Abhängigkeit von den solaren Beleuchtung- und Blickrichtungsgeometrien führen.
Zielstellung dieser Arbeit ist die hyperspektrale und spektro-direktionale Charakterisierung der Oberflächenreflexion wichtiger und repräsentativer arktischer Pflanzengesellschaften in Sibirien und Alaska, als Grundlage für die Extraktion von Vegetationsparametern und die Normalisierung von BRDF-Effekten in Off-Nadir und multi-temporalen Fernerkundungsdaten. In Vorbereitung auf die bevorstehende nationale EnMAP Satellitenmission ist ein Grundverständnis der BRDF-Effekte in der arktischen Tundra von wesentlicher Bedeutung für die Erstellung von hochqualitativen, konsistenten und damit vergleichbaren Datensätzen. Die in dieser Arbeit genutzten Daten beruhen auf geländespektroskopische und geländespektro-goniometrische Untersuchungen von repräsentativen Messflächen in Sibirien und Alaska.
Die Entwicklung eines leichten, transportablen und einfach anzuwendenden Geländespektro-Goniometers, welches dennoch zuverlässig Daten liefert, war die erste Aufgabe. Hierfür habe ich ein Gerät mit der Bezeichnung ManTIS („Manual Transportable Instrument platform for ground-based Spectro-directional observations“) entwickelt.
Die Ergebnisse der geländespektro-radiometrischen Messungen entlang wichtiger ökologischer Gradienten (regionales Klima, pH-Wert des Bodens, Bodenfeuchte, Toposequenz) zeigen, dass die Pflanzengesellschaften sich anhand ihrer Nadir-Reflektanzen unterscheiden lassen. Insbesondere die Möglichkeit der Differenzierung im sichtbaren (VIS) blauen und roten Wellenlängenbereich. Die Nah-Infrarot (NIR) Schulter und das NIR-Reflektanzplateau sind trotz ihrer niedrigeren Reflektanzwerte eine wertvolle Informationsquelle, die genutzt werden kann um die Pflanzengesellschaften entsprechend ihrer Biomasse und der Vegetationsstruktur voneinander zu unterscheiden. Im Allgemeinen zeigen die verschiedenen Pflanzengesellschaften der Tundra: (i) eine niedrige maximale NIR-Reflektanz; (ii) ein schwaches oder nicht sichtbares lokales Reflektanzmaximum im grünen VIS-Spektrum; (iii) einen schmalen „red-edge“ Bereich zwischen dem roten und NIR-Wellenlängenbereich und (iv) kein deutliches NIR-Reflektanzplateau.
Diese gemeinsamen Nadir-Reflektanzeigenschaften sind entscheidend für das Verständnis der Variabilität der BRDF-Effekte in der arktischen Tundra. Keine der untersuchten Pflanzengesellschaften wies isotrope Reflektanzeigenschaften auf. Im Allgemeinen zeigt Tundravegetation: (i) die höchsten BRDF-Effekte in der solaren Hauptebene; (ii) die maximalen Reflexionsgrade in den rückwärts gerichteten Blickrichtungen; (iii) höhere Grade an Anisotropie im VIS-Spektrum als im NIR-Spektrum und (iv) schüsselförmige Reflexionsgradverteilungen in den längeren Wellenlängenbereichen (>700 nm). Die Analyse des Einflusses von hohen Sonnenzenitwinkeln auf die Anisotropie der Rückstrahlung zeigt, dass sich mit zunehmenden Sonnenzenitwinkeln die Anisotropie-Eigenschaften in azimutal-symmetrische schüsselförmige Reflexionsgradverteilungen ändern.
Auch ergeben die spektro-direktionalen Analysen, dass Fernerkundungsprodukte wie der NDVI oder die relative Absorptionstiefe stark von BRDF-Effekten beeinflusst werden. Die anisotropen Eigenschaften der Fernerkundungsprodukte können sich erheblich von den beobachteten BRDF-Effekten in den ursprünglichen Reflektanzdaten unterscheiden. Auch lässt sich aus den Ergebnissen ableiten, dass der NDVI relativ gesehen die blickrichtungsabhängigen BRDF-Effekte minimieren kann. Für die untersuchten Pflanzengesellschaften der Tundra weichen die Off-Nadir NDVI-Werte nie mehr als 10 % von den Nadir-NDVI-Werten ab.
Im Resümee dieser Studie wird nachgewiesen, dass Änderungen in der Sonnen-Objekt-Sensor-Geometrie direkt zu Reflektanzveränderungen in den Fernerkundungsdaten von arktischen Pflanzengesellschaften der Tundra entsprechend ihrer objekt-spezifischen BRDF-Charakteristiken führen. Da die verschiedenen Arten der Tundravegetation nur kleine, aber signifikante Unterschiede in der Oberflächenreflektanz zeigen, ist es wichtig die spektro-direktionalen Reflexionseigenschaften bei der Entwicklung von Algorithmen für Fernerkundungsprodukte zu berücksichtigen.
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Young, Cindy L. "A satellite and ash transport model aided approach to assess the radiative impacts of volcanic aerosol in the Arctic." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53404.
Full textAbstract:
The Arctic radiation climate is influenced substantially by anthropogenic and natural aerosols. There have been numerous studies devoted to understanding the radiative impacts of anthropogenic aerosols (e.g. those responsible for producing the Arctic haze phenomenon) and natural aerosols (e.g. dust and smoke) on the Arctic environment, but volcanic aerosols have received less attention. Volcanic eruptions occur frequently in the Arctic and have the capacity to be long duration, high intensity events, expelling large amounts of aerosol-sized ash and gases, which form aerosols once in the atmosphere. Additionally, volcanic eruptions deposit ash, which can alter the surface reflectivity, and remain to influence the radiation balance long after the eruptive plume has passed over and dissipated. The goal of this dissertation is to quantify the radiative effects of volcanic aerosols in the Arctic caused by volcanic plumes and deposits onto ice and snow covered surfaces.
The shortwave, longwave, and net direct aerosol radiative forcing efficiencies and atmospheric heating/cooling rates caused by volcanic aerosol from the 2009 eruption of Mt. Redoubt were determined by performing radiative transfer modeling constrained by NASA A-Train satellite data. The optical properties of volcanic aerosol were calculated by introducing a compositionally resolved microphysical model developed for both ash and sulfates. Two compositions of volcanic aerosol were considered in order to examine a fresh, ash rich plume and an older, ash poor plume. The results indicate that environmental conditions, such as surface albedo and solar zenith angle, can influence the sign and the magnitude of the radiative forcing at the top of the atmosphere and at the surface. Environmental conditions can also influence the magnitude of the forcing in the aerosol layer. For instance, a fresh, thin plume with a high solar zenith angle over snow cools the surface and warms the top of the atmosphere, but the opposite effect is seen by the same layer over ocean. The layer over snow also warms more than the same plume over seawater. It was found that plume aging can alter the magnitude of the radiative forcing. For example, an aged plume over snow at a high solar zenith angle would warm the top of the atmosphere and layer by less than the fresh plume, while the aged plume cools the surface more. These results were compared with those reported for other aerosols typical to the Arctic environment (smoke from wildfires, Arctic haze, and dust) to demonstrate the importance of volcanic aerosols. It is found that the radiative impacts of volcanic aerosol plumes are comparable to those of other aerosol types, and those compositions rich in volcanic ash can have greater impacts than other aerosol types.
Volcanic ash deposited onto ice and snow in the Arctic has the potential to perturb the regional radiation balance by altering the surface reflectivity. The areal extent and loading of ash deposits from the 2009 eruption of Mt. Redoubt were assessed using an Eulerian volcanic ash transport and dispersion model, Fall3D, combined with satellite and deposit observations. Because observations are often limited in remote Arctic regions, we devised a novel method for modeling ash deposit loading fields for the entire eruption based on best-fit parameters of a well-studied eruptive event. The model results were validated against NASA A-train satellite data and field measurements reported by the Alaska Volcano Observatory. Overall, good to moderate agreement was found. A total cumulative deposit area of 3.7 X 10^6 km2 was produced, and loadings ranged from ~7000 ± 3000 gm-2 near the vent to <0.1 ± 0.002 gm-2 on the outskirts of the deposits. Ash loading histories for total deposits showed that fallout ranged from ~5 – 17 hours. The deposit loading results suggest that ash from short duration events can produce regionally significant deposits hundreds of kilometers from the volcano, with the potential of significantly modifying albedo over wide regions of ice and snow covered terrain.
The solar broadband albedo change, surface radiative forcing, and snowmelt rates associated with the ash deposited from the 2009 eruption of Mt. Redoubt were calculated using the loadings from Fall3D and the snow, ice, and aerosol radiative models. The optical properties of ash were calculated from Mie theory, based on size information recovered from the Fall3D model. Two sizes of snow were used in order to simulate a young and old snowpack. Deposited ash sizes agree well with field measurements. Only aerosol-sized ashes in deposits were considered for radiative modeling, because larger particles are minor in abundance and confined to areas very close to the vent. The results show concentrations of ash in snow range from ~ 6.9x10^4 – 1x10^8 ppb, with higher values closer to the vent and lowest at the edge of the deposits, and integrated solar albedo reductions of ~ 0 – 59% for new snow and ~ 0 – 85% for old snow. These albedo reductions are much larger than those typical for black carbon, but on the same order of magnitude as those reported for volcanic deposits in Antarctica. The daily mean surface shortwave forcings associated with ash deposits on snow ranged from 0 – 96 Wm-2 from the outmost deposits to the vent. There were no significantly accelerated snowmelts calculated for the outskirts of the deposits. However, for areas of higher ash loadings/concentrations, daily melt rates are significantly higher (~ 220 – 320%) because of volcanic ash deposits.
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Marchand, Nicolas. "Suivi de la température de surface du sol en zones de pergélisol Arctique par l'utilisation de données de télédétection satellite assimilées dans le schéma de surface du modèle climatique canadien (CLASS)." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAU018/document.
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Plusieurs études récentes ont montré que le réchauffement climatique des régions nordiques, deux fois plus important dans les hautes latitudes nord qu’ailleurs dans le monde, augmentait l’épaisseur de la couche active de surface en zones de pergélisol (couche superficielle du sol qui dégèle durant la période estivale). Cette modification de surface pourrait avoir un impact environnemental très important sur la libération du carbone du sol, l’hydrologie, les écosystèmes, ainsi que sur le pergélisol. Cette évolution commence déjà à avoir des répercutions socio-économiques importantes sur les infrastructures des communautés du Nord. Le but du projet est d’exploiter une nouvelle base de données satellites micro-onde, que nous venons de développer, pour l’analyse des températures de surface et de l’évolution du pergélisol (permafrost) au Canada-Alaska sur les 30 dernières années. Un des objectifs spécifiques du projet est de mettre au point une méthode de caractérisation des changements de la couche active de surface en zones de pergélisol par l’assimilation des observations spatiales dans un modèle de flux de chaleur dans le sol. L’évolution de l’étendue des zones de pergélisol dérivée sera analysée en fonction de la couverture du sol et de la dynamique du couvert nival, deux paramètres aussi dérivés par satellite. Possibilité de validation des modèles par mesures au sol avec nos radiomètres micro-ondes. Ce projet combine ainsi développement théorique, modélisation et traitement d’images numériques sur différents domaines scientifiques (physique de la mesure en télédétection, géophysique de l’environnement, écosystèmes, science des sols)<br>Recent studies showed that global warming in arctic areas, as twice as important in northern high latitudes than in the rest of the world, growed the thickness of the surface active layer in permafrost areas (superficial layer of the soil that thaws during summer period). This surface modification could have a major environmental impact on soil carbon release, hydrology, ecosystems, and permafrost. It already starts to have socio-economical impacts on north community infrastructures. The project's goal is to use a new microwave satellite database that has just been developed for the analysis of surface temperatures and changes in permafrost in Canada, Alaska over the past 30 years. One of the specific goals of the project is to develop a method to characterize changes in the surface active layer in permafrost areas by the assimilation of space observations in a heat flow model in the soil. The evolution of the extension of permafrost areas derived will be analyzed according to the coverage of soil and the dynamics of snow cover, two parameters also derived by satellite. Possibility of model validation by ground measurements with a microwaves radiometers. This project combines theoretical development, modeling and image processing on different scientific fields (physics of remote sensing measurement, Geophysics of the Environment, ecosystems, soil science)
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Beamish, Alison Leslie [Verfasser], Hugues [Akademischer Betreuer] Lantuit, Hugues [Gutachter] Lantuit, Birgit [Gutachter] Heim, and Paul [Gutachter] Treitz. "Hyperspectral remote sensing of the spatial and temporal heterogeneity of low Arctic vegetation : the role of phenology, vegetation colour, and intrinsic ecosystem components / Alison Leslie Beamish ; Gutachter: Hugues Lantuit, Birgit Heim, Paul Treitz ; Betreuer: Hugues Lantuit." Potsdam : Universität Potsdam, 2019. http://d-nb.info/121914990X/34.
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Beamish, Alison Leslie [Verfasser], Hugues Akademischer Betreuer] Lantuit, Hugues [Gutachter] Lantuit, Birgit [Gutachter] Heim, and Paul Michael [Gutachter] [Treitz. "Hyperspectral remote sensing of the spatial and temporal heterogeneity of low Arctic vegetation : the role of phenology, vegetation colour, and intrinsic ecosystem components / Alison Leslie Beamish ; Gutachter: Hugues Lantuit, Birgit Heim, Paul Treitz ; Betreuer: Hugues Lantuit." Potsdam : Universität Potsdam, 2019. http://d-nb.info/121914990X/34.
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Beamish, Alison Leslie [Verfasser], Hugues [Akademischer Betreuer] Lantuit, Hugues Gutachter] Lantuit, Birgit [Gutachter] Heim, and Paul Michael [Gutachter] [Treitz. "Hyperspectral remote sensing of the spatial and temporal heterogeneity of low Arctic vegetation : the role of phenology, vegetation colour, and intrinsic ecosystem components / Alison Leslie Beamish ; Gutachter: Hugues Lantuit, Birgit Heim, Paul Treitz ; Betreuer: Hugues Lantuit." Potsdam : Universität Potsdam, 2019. http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-425922.
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Tamstorf, Mikkel P. "Satellitbaseret vegetationskortlægning i Vestgrønland." [København] : Miljø- og Energiministeriet, Danmarks Miljøundersøgelser, 2001. http://www.dmu.dk/1_viden/2_Publikationer/3_Ovrige/rapporter/PHD_mpt.pdf.
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Dupont, Florent. "Télédétection micro-onde de surfaces enneigées en milieu arctique : étude des processus de surface de la calotte glaciaire Barnes, Nunavut, Canada." Phd thesis, Université de Grenoble, 2013. http://tel.archives-ouvertes.fr/tel-01070037.
Full textAbstract:
La région de l'archipel canadien, située en Arctique, connaît actuellement d'importants changements climatiques, se traduisant notamment par une augmentation des températures, une réduction de l'étendue de la banquise marine et du couvert nival terrestre ou encore une perte de masse significative des calottes glaciaires disséminées sur les îles de l'archipel. Parmi ces calottes glaciaires, la calotte Barnes, située en Terre de Baffin, ne fait pas exception comme le montrent les observations satellitaires qui témoignent d'une importante perte de masse ainsi que d'une régression de ses marges, sur les dernières décennies. Bien que les calottes glaciaires de l'archipel canadien ne représentent que quelques dizaines de centimètres d'élévation potentielle du niveau des mers, leur perte de masse est une composante non négligeable de l'augmentation actuelle du niveau des mers. Les projections climatiques laissent à penser que cette contribution pourrait rester significative dans les décennies à venir. Cependant, afin d'estimer les évolutions futures de ces calottes glaciaires et leur impact sur le climat ou le niveau des mers, ils est nécessaire de caractériser les processus physiques tels que les modifications du bilan de masse de surface. Cette connaissance est actuellement très limitée du fait notamment du sous-échantillonnage des régions arctiques en terme de stations météorologiques permanentes. Une autre particularité de certaines calottes de l'archipel canadien, et de la calotte Barnes en particulier, est de présenter un processus d'accumulation de type glace surimposée, ce phénomène étant à prendre en compte dans l'étude des processus de surface. Pour palier au manque de données, l'approche retenue a été d'utiliser des données de télédétection, qui offrent l'avantage d'une couverture spatiale globale ainsi qu'une bonne répétitivité temporelle. En particulier les données acquises dans le domaine des micro-ondes passives est d'un grand intérêt pour l'étude de surfaces enneigées. En complément de ces données, la modélisation du manteau neigeux, tant d'un point de vue des processus physiques que de l'émission électromagnétique permet d'avoir accès à une compréhension fine des processus de surface tels que l'accumulation de la neige, la fonte, les transferts d'énergie et de matière à la surface, etc. Ces différents termes sont regroupés sous la notion de bilan de masse de surface. L'ensemble du travail présenté dans ce manuscrit a donc consisté à développer des outils permettant d'améliorer la connaissance des processus de surface des calottes glaciaires du type de celles que l'on rencontre dans l'archipel canadien, l'ensemble du développement méthodologique ayant été réalisé sur la calotte Barnes à l'aide du schéma de surface SURFEX-CROCUS pour la modélisation physique et du modèle DMRT-ML pour la partie électromagnétique. Les résultats ont tout d'abord permis de mettre en évidence une augmentation significative de la durée de fonte de surface sur la calotte Barnes (augmentation de plus de 30% sur la période 1979-2010), mais aussi sur la calotte Penny, elle aussi située en Terre de Baffin et qui présente la même tendance (augmentation de l'ordre de 50% sur la même période). Ensuite, l'application d'une chaîne de modélisation physique contrainte par diverses données de télédétection a permis de modéliser de manière réaliste le bilan de masse de surface de la dernière décennie, qui est de +6,8 cm/an en moyenne sur la zone sommitale de la calotte, qui est une zone d'accumulation. Enfin, des tests de sensibilité climatique sur ce bilan de masse ont permis de mettre en évidence un seuil à partir duquel cette calotte voit disparaître sa zone d'accumulation. Les modélisations effectuées suggèrent que ce seuil a de fortes chances d'être atteint très prochainement, pour une augmentation de température moyenne inférieure à 1°C, ce qui aurait pour conséquence une accélération de la perte de masse de la calotte.
44
Montpetit, Benoît. "Analyse de la modélisation de l'émission multi-fréquences micro-onde des sols et de la neige, incluant les croutes de glace à l'aide du modèle Microwave Emission Model of Layered Snowpacks (MEMLS)." Thèse, Université de Sherbrooke, 2015. http://hdl.handle.net/11143/6844.
Full textAbstract:
Résumé : L'étude du couvert nival est essentielle afin de mieux comprendre les processus climatiques et hydrologiques. De plus, avec les changements climatiques observés dans l'hémisphère nord, des événements de dégel-regel ou de pluie hivernale sont de plus en plus courants et produisent des croutes de glace dans le couvert nival affectant les moeurs des communautés arctiques en plus de menacer la survie de la faune arctique. La télédétection micro-ondes passives (MOP) démontre un grand potentiel de caractérisation du couvert nival. Toutefois, a fin de bien comprendre les mesures satellitaires, une modélisation adéquate du signal est nécessaire. L'objectif principal de cette thèse est d'analyser le transfert radiatif (TR) MOP des sols, de la neige et de la glace a fin de mieux caractériser les propriétés géophysiques du couvert nival par télédétection. De plus, un indice de détection des croutes de glace par télédétection MOP a été développé. Pour ce faire, le modèle Microwave Emission Model of Layered Snowpacks (MEMLS) a été étudié et calibré afin de minimiser les erreurs des températures de brillance simulées en présences de croutes de glace.
La première amélioration faite à la modélisation du TR MOP de la neige a été la caractérisation de la taille des grains de neige. Deux nouveaux instruments, utilisant la réflectance dans le proche infrarouge, ont été développés afin de mesurer la surface spécifique de la neige (SSA). Il a été démontré que la SSA est un paramètre plus précis et plus objectif pour caractériser la taille des grains de neige. Les deux instruments ont démontré une incertitude de 10% sur la mesure de la SSA. De plus, la SSA a été calibré pour la modélisation MOP a n de minimiser l'erreur sur la modélisation de la température de brillance. Il a été démontré qu'un facteur multiplicatif [phi] = 1.3 appliqué au paramètre de taille des grains de neige dans MEMLS, paramètre dérivé de la SSA, est nécessaire afin de minimiser l'erreur des simulations.
La deuxième amélioration apportée à la modélisation du TR MOP a été l'estimation de
l'émission du sol. Des mesures radiométriques MOP in-situ ainsi que des profils de températures de sols organiques arctiques gelés ont été acquis et caractérisés a fin de simuler l'émission MOP de ces sols. Des constantes diélectriques effectives à 10.7, 19 et 37 GHz ainsi qu'une rugosité de surface effective des sols ont été déterminés pour simuler l'émission des sols. Une erreur quadratique moyenne (RMSE) de 4.65 K entre les simulations et les mesures MOP a été obtenue.
Suite à la calibration du TR MOP du sol et de la neige, un module de TR de la glace a
été implémenté dans MEMLS. Avec ce nouveau module, il a été possible de démontré que l'approximation de Born améliorée, déjà implémenté dans MEMLS, pouvait être utilisé pour simuler des croutes de glace pure à condition que la couche de glace soit caractérisée par une densité de 917 kg m[indice supérieur _3] et une taille des grains de neige de 0 mm. Il a aussi été démontré que, pour des sites caractérisés par des croutes de glace, les températures de brillances simulées des couverts de neige avec des croutes de glace ayant les propriétés mesurées in-situ (RMSE=11.3 K), avaient une erreur similaire aux températures de brillances simulées des couverts de neige pour des sites n'ayant pas de croutes de glace (RMSE=11.5 K).
Avec le modèle MEMLS validé pour la simulation du TR MOP du sol, de la neige et de la
glace, un indice de détection des croutes de glace par télédétection MOP a été développé. Il a été démontré que le ratio de polarisation (PR) était très affecté par la présence de croutes de glace dans le couvert de neige. Avec des simulations des PR à 10.7, 19 et 37 GHz sur des sites mesurés à Churchill (Manitoba, Canada), il a été possible de déterminer des seuils entre la moyenne hivernale des PR et les valeurs des PR mesurés indiquant la présence de croutes de glace. Ces seuils ont été appliqués sur une série temporelle de PR de 33 hivers d'un pixel du Nunavik (Québec, Canada) où les conditions de sols étaient similaires à ceux observés à Churchill. Plusieurs croutes de glace ont été détectées depuis 1995 et les mêmes événements entre 2002 et 2009 que (Roy, 2014) ont été détectés. Avec une validation in-situ, il serait possible de confirmer ces événements de croutes de glace mais (Roy, 2014) a démontré que ces événements ne pouvaient être expliqués que par la présence de croutes de glace dans le couvert de neige. Ces mêmes seuils sur les PR ont été appliqués sur un pixel de l'Île Banks
(Territoires du Nord-Ouest, Canada). L'événement répertorié par (Grenfell et Putkonen,
2008) a été détecté. Plusieurs autres événements de croutes de glace ont été détectés dans les années 1990 et 2000 avec ces seuils. Tous ces événements ont suivi une période où les températures de l'air étaient près ou supérieures au point de congélation et sont rapidement retombées sous le point de congélation. Les températures de l'air peuvent être utilisées pour confirmer la possibilité de présence de croutes de glace mais seul la validation in-situ peut définitivement confirmer la présence de ces croutes.<br>Abstract : Snow cover studies are essential to better understand climatic and hydrologic processes. With
recent climate change observed in the northern hemisphere, more frequent rain-on-snow and meltrefreeze
events have been reported, which affect the habits of the northern comunities and the
survival of arctique wildlife. Passive microwave remote sensing has proven to be a great tool to
characterize the state of snow cover. Nonetheless, proper modeling of the microwave signal is needed
in order to understand how the parameters of the snowpack affect the measured signal.
The main objective of this study is to analyze the soil, snow and ice radiative transfer in order
to better characterize snow cover properties and develop an ice lens detection index with satellite
passive microwave brightness temperatures. To do so, the passive microwave radiative transfer
modeling of the Microwave Emission Model of Layered Snowpacks (MEMLS) was improved
in order to minimize the errors on the brightness temperature simulations in the presence of ice
lenses.
The first improvement to passive microwave radiative transfer modeling of snow made was the
snow grain size parameterization. Two new instruments, based on short wave infrared reflectance
to measure the snow specific surface area (SSA) were developed. This parameter was shown to
be a more accurate and objective to characterize snow grain size. The instruments showed an
uncertainty of 10% to measure the SSA of snow. Also, the SSA of snow was calibrated for passive
microwave modeling in order to reduce the errors on the simulated brightness temperatures. It was
showed that a correction factor of φ = 1.3 needed to be applied to the grain size parameter of
MEMLS, obtain through the SSA measurements, to minimize the simulation error.
The second improvement to passive microwave radiative transfer modeling was the estimation
of passive microwave soil emission. In-situ microwave measurements and physical temperature
profiles of frozen organic arctic soils were acquired and characterized to improve the modeling of
the soil emission. Effective permittivities at 10.7, 19 and 37 GHz and effective surface roughness
were determined for this type of soil and the soil brightness temperature simulations were obtain
with a minimal root mean square error (RMSE) of 4.65K.
With the snow grain size and soil contributions to the emitted brightness temperature optimized, it
was then possible to implement a passive microwave radiative transfer module of ice into MEMLS.
With this module, it was possible to demonstrate that the improved Born approximation already
implemented in MEMLS was equivalent to simulating a pure ice lens when the density of the layer
was set to 917 kg m−3
and the grain size to 0 mm. This study also showed that by simulating
ice lenses within the snow with there measured properties, the RMSE of the simulations (RMSE=
11.3 K) was similar to the RMSE for simulations of snowpacks where no ice lenses were measured
(only snow, RMSE= 11.5 K).
With the validated MEMLS model for snowpacks with ice lenses, an ice index was created. It
is shown here that the polarization ratio (PR) was strongly affected by the presence of ice lenses
within the snowpack. With simulations of the PR at 10.7, 19 and 37 GHz from measured snowpack
properties in Chucrhill (Manitoba, Canada), thresholds between the measured PR and the mean
winter PR were determined to detect the presence of ice within the snowpack. These thresholds
were applied to a timeseries of nearly 34 years for a pixel in Nunavik (Quebec, Canada) where the
soil surface is similar to that of the Churchill site. Many ice lenses are detected since 1995 with
these thresholds and the same events as Roy (2014) were detected. With in-situ validation, it would
be possible to confirm the precision of these thresholds but Roy (2014) showed that these events
can not be explained by anything else than the presence of an ice layer within the snowpack. The
same thresholds were applied to a pixel on Banks island (North-West Territories, Canada). The
2003 event that was reported by Grenfell et Putkonen (2008) was detected by the thresholds. Other
events in the years 1990 and 2000’s were detected with these thresholds. These events all follow
periods where the air temperature were warm and were followed by a quick drop in air temperature
which could be used to validate the presence of ice layer within the snowpack. Nonetheless, without
in-situ validation, these events can not be confirmed.
45
Vargel, Céline. "Caractérisation du manteau neigeux arctique, suivi climatique et télédétection micro-onde." Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALU029.
Full textAbstract:
Les régions de hautes latitudes nord se réchauffent de façon plus intense que sur le reste du globe. Ce phénomène, appelé amplification arctique, est dû en partie à la diminution de l'étendue de glace de mer et de la couverture de neige. Par ses changements de pouvoirs réfléchissant et isolant, la neige, présente 9 mois de l'année, pourrait avoir un effet important sur l'augmentation des températures du sol. Le dégel du pergélisol à travers le carbone ainsi libéré serait susceptible d'avoir un impact important sur le climat futur de l'Arctique. Ce projet de recherche a pour objectif d'améliorer le suivi du couvert nival arctique et des températures du sol. À l'heure actuelle, les modèles détaillés d'évolution du manteau neigeux tels que le modèle Crocus ne parviennent pas à reproduire la physique particulière de la neige arctique ce qui conduit à des incertitudes importantes dans la modélisation des températures du sol. De nouvelles paramétrisations physiques ont été implémentées au sein du modèle Crocus pour améliorer la stratification verticale du manteau neigeux en introduisant les effets de la végétation (neige moins dense en profondeur) et les effets du vent (neige plus dense en surface), ainsi que pour modifier la conductivité thermique de la neige. Ces nouvelles paramétrisations permettent une meilleure représentation des températures du sol sous la neige, validée avec un large jeu de données en Alaska, dans l'Arctique canadien et en Sibérie. Les simulations ainsi réalisées à l'aide du modèle Crocus modifié, piloté par la réanalyse météorologique ERA-Interim sur les 39 dernières années (1979-2018), à l'échelle panarctique, montrent une augmentation significative de la densité de la neige au printemps ainsi que de l'humidité de la neige principalement au printemps et en automne, accompagnée d'une diminution significative de la durée d'enneigement. Ces effets cumulés à l'augmentation des températures de l'air entraînent une augmentation des températures du sol allant jusqu'à +0.89 K par décade pour le mois de juin. De façon à pouvoir améliorer le suivi de l'évolution spatiale et temporelle du couvert nival, l'utilisation de données d'observations satellitaires micro-onde est proposée. À partir de l'analyse d'un jeu de données unique de mesures radiométriques en surface associées à la caractérisation in-situ du manteau neigeux (119 snowpits avec des observations simultanées) en zone arctique et subarctique, une paramétrisation optimale du modèle de transfert radiatif SMRT a été définie. En utilisant une longueur de corrélation exponentielle ajustée comme paramètre de microstructure de la neige dans le modèle électromagnétique Improved Born Approximation (IBA), l'étude montre, par rapport aux autres configurations de modèles testées, de meilleurs résultats avec une erreur moyenne (RMSE) inférieure à 30% des observations pour la neige subarctique et 24% pour la neige arctique. Couplées à Crocus, les températures de brillance simulées sur l'ensemble de l'Arctique sont significativement meilleures avec Crocus modifié qu'avec Crocus standard (38 K d'amélioration de l'erreur en moyenne). Ces résultats ouvrent la voie à l'utilisation de l'assimilation des observations micro-onde satellitaires dans le modèle Crocus à grande échelle afin d'améliorer les simulations de densité de la neige arctique, paramètre clef du manteau neigeux influant sur l'évolution des températures du sol sous la neige<br>Northern high-latitude regions are warming more intensely than the rest of the world. This phenomenon, called Arctic amplification, is due in part to the decrease in sea ice extent and snow cover. Snow, which is present 9 months of the year, could have a significant effect on the increase in land surface temperatures by changing its reflective and insulating properties. Thawing of permafrost which could release important amount of soil carbone into the atmosphere could have a significant positive feedback on the future climate of the Arctic. The objective of this research project is to improve the monitoring of Arctic snow cover and ground temperatures. Detailed models of snow cover evolution such as the Crocus multi-layered model are unable to reproduce the particular physics of Arctic snow, which leads to significant uncertainties in the modeling of ground temperatures. New physical parameterizations have been implemented within the Crocus model to improve the vertical stratification of the snowpack by introducing vegetation effects (less dense snow at the bottom) and wind effects (denser snow at the surface), as well as to modify the thermal conductivity of snow. These new parameterizations allow a better representation of ground temperatures under the snowpack, validated with a large dataset in Alaska, Canadian Arctic and Siberia. The simulations thus carried out using the modified Crocus model, driven by the ERA-Interim meteorological reanalysis over the last 39 years (1979-2018), at the pan-Arctic scale, show a significant increase in snow density in spring as well as in snow moisture, mainly in spring and fall, accompanied by a significant decrease in the duration of the snow cover. These effects, combined with the increase in air temperature, lead to an increase in ground temperature of up to +0.89 K per decade for the month of June. In order to improve monitoring the spatial and temporal evolution of the snow cover, the use of microwave satellite observation data is proposed. Based on the analysis of a unique dataset of surface radiometric measurements, associated with the in-situ characterization of the snowpit (119 snowpits with simultaneous observations) in the Arctic and sub-Arctic zones, an optimal parameterization of the SMRT model has been defined. The results show that using a fitted exponential correlation length as a snow microstructure parameter in the Improved Born Approximation (IBA) electromagnetic model gives the best results compared to the other model configurations tested, with a mean error (RMSE) of less than 30% of the observations for subarctic snow and 24% for Arctic snow. Coupled with Crocus, the simulated brightness temperatures over the entire Arctic are significantly better with modified Crocus than with standard Crocus (38 K improvement in mean bias). These results pave the way for using the assimilation of satellite microwave observations into the Crocus model to improve simulations of Arctic snow density, a key snowpack parameter influencing the evolution of ground temperatures under the snow
46
Dupont, Florent. "Télédétection micro-onde de surfaces enneigées en milieu arctique : étude des processus de surface de la calotte glaciaire Barnes, Nunavut, Canada." Thèse, Université de Sherbrooke, 2014. http://savoirs.usherbrooke.ca/handle/11143/5306.
Full textAbstract:
Résumé : La région de l'archipel canadien, située en Arctique, connaît actuellement d'importants changements climatiques, se traduisant notamment par une augmentation des températures, une réduction de l'étendue de la banquise marine et du couvert nival terrestre ou encore une perte de masse significative des calottes glaciaires disséminées sur les îles de l'archipel. Parmi ces calottes glaciaires, la calotte Barnes, située en Terre de Baffin, ne fait pas exception comme le montrent les observations satellitaires qui témoignent d'une importante perte de masse ainsi que d'une régression de ses marges, sur les dernières décennies.
Bien que les calottes glaciaires de l'archipel canadien ne représentent que quelques dizaines de centimètres d'élévation potentielle du niveau des mers, leur perte de masse est une composante non négligeable de l'augmentation actuelle du niveau des mers. Les projections climatiques laissent à penser que cette contribution pourrait rester significative dans les décennies à venir. Cependant, afin d'estimer les évolutions futures de ces calottes glaciaires et leur impact sur le climat ou le niveau des mers, il est nécessaire de caractériser les processus physiques tels que les modifications du bilan de masse de surface. Cette connaissance est actuellement très limitée du fait notamment du sous-échantillonnage des régions arctiques en terme de stations météorologiques permanentes.
Une autre particularité de certaines calottes de l'archipel canadien, et de la calotte Barnes en particulier, est de présenter un processus d'accumulation de type glace surimposée, ce phénomène étant à prendre en compte dans l'étude des processus de surface.
Pour pallier au manque de données, l'approche retenue a été d'utiliser des données de télédétection, qui offrent l'avantage d'une couverture spatiale globale ainsi qu'une bonne répétitivité temporelle. En particulier les données acquises dans le domaine des micro-ondes passives sont d'un grand intérêt pour l'étude de surfaces enneigées. En complément de ces données, la modélisation du manteau neigeux, tant d'un point de vue des processus physiques que de l'émission électromagnétique permet d'avoir accès à une compréhension fine des processus de surface tels que l'accumulation de la neige, la fonte, les transferts d'énergie et de matière à la surface, etc. Ces différents termes sont regroupés sous la notion de bilan de masse de surface. L'ensemble du travail présenté dans ce manuscrit a donc consisté à développer des outils permettant d'améliorer la connaissance des processus de surface des calottes glaciaires du type de celles que l'on rencontre dans l'archipel canadien, l'ensemble du développement méthodologique ayant été réalisé sur la calotte Barnes à l'aide du schéma de surface SURFEX-CROCUS pour la modélisation physique et du modèle DMRT-ML pour la partie électromagnétique.
Les résultats ont tout d'abord permis de mettre en évidence une augmentation significative de la durée de fonte de surface sur la calotte Barnes (augmentation de plus de 30% sur la période 1979-2010), mais aussi sur la calotte Penny, elle aussi située en Terre de Baffin et qui présente la même tendance (augmentation de l'ordre de 50% sur la même période).
Ensuite, l'application d'une chaîne de modélisation physique contrainte par diverses données de télédétection a permis de modéliser de manière réaliste le bilan de masse de surface de la dernière décennie, qui est de +6,8 cm/an en moyenne sur la zone sommitale de la calotte, qui est une zone d'accumulation. Enfin, des tests de sensibilité climatique sur ce bilan de masse ont permis de mettre en évidence un seuil à partir duquel cette calotte voit disparaître sa zone d'accumulation. Les modélisations effectuées suggèrent que ce seuil a de fortes chances d'être atteint très prochainement, pour une augmentation de température moyenne inférieure à 1°C, ce qui aurait pour conséquence une accélération de la perte de masse de la calotte.
// Abstract : Significant climate change is curently monitored in the Arctic, and especially in the
region of the canadian arctic archipellago. This climate warming leads to recession of seaice
extent and seasonnal snow cover, and also to large mass loss of the archipellago’s ice
caps. One of the most southern ice cap, the Barnes Ice Cap, located on the Baffin Island,
is no exception to significant mass loss and margins recession as satellite observations
exhibited over the last decades.
Despite the relative low sea level potential of the small ice caps located in the canadian
arctic achipellago in regards to major ice sheets, Antarctica and Greenland, their
contribution to the current sea level rise is significant. Climate projections show that this
contribution could accelerate significant over the next decades. However, to estimate the
future evolution of these ice caps and their impact on climate or sea level rise, a better
characterisation of the surface processes such as the evolution of the surface mass balance
is needed. This knowledge is currently very limited, mainly due to the sparse covering of
automatic weather stations or in-situ measurements over the Arctic. Furthermore, several
ice caps, among with the Barnes Ice Cap, present a superimposed ice accumulation area
which particularities have to be taken into account in the surface processes studies.
Given the lack of in-situ data, the approach choosen in this work is to use remote sensing
data, that have the advantage to offer a good spatial and temporal coverage. In particular,
passive microwave data are very suitable for snowy surfaces studies. To complement
these data, physical and electromagnetic snowpack modeling provide a fine characterisation
of surface processes such as snow accumulation. The whole work presented in this
manuscript thus consisted in developping specific tools to improve the understanding of
surface processes of small arctic ice caps. This methodological development was performed
and applied on the Barnes Ice Cap using the surface scheme SURFEX-CROCUS and the
electromagnetic model DMRT-ML.
First results highlight a significant increase in surface melt duration over the past 3
decades on the Barnes Ice Cap (increase of more than 30% over 1979-2010 period). A
similar trend is also monitored over the Penny Ice Cap, located in the south part of the
Baffin Island (increase of more than 50% over the same period).
Then, the surface mass balance over the last decade was modeled by using a physical
based modeling chain constrained by remote sensing data. The results give a mean net
accumulation of +6,8 cm y−1 on the summit area of the ice cap. Finaly, sensitivity tests,
performed to investigate the climatic sensitivity of the surface mass balance, highlight a
threshold effect that may lead to a complete disapearence of the accumulation area of the
Barnes Ice Cap. With a temperature increase less than 1°C, modeling results suggest it is
likely that the threshold will be reached rapidly leading to an increase in mass loss from
the ice cap.
47
Padovanni, Naia Godoy [UNESP]. "Análise espacial da temperatura e albedo de superfície em bacias hidrográficas." Universidade Estadual Paulista (UNESP), 2017. http://hdl.handle.net/11449/151949.
Full textAbstract:
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Previous issue date: 2017-09-01<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)<br>O estudo dos fenômenos atmosféricos requer a compreensão de complexas relações e interações dos sistemas naturais e/ou antrópicos. As alterações da superfície terrestre alteram os processos de troca de energia entre a superfície e atmosfera em diferentes escalas, atuando na variação de temperatura da superfície e do ar, na intensidade dos fluxos de energia disponível na superfície e nas variações da energia armazenada na vegetação. A utilização de técnicas de sensoriamento remoto na compreensão dessas relações, a partir de uma abordagem geossistêmica, auxilia otimizando a obtenção de dados, no refinamento e acurácia destes e na análise sistêmica, tornando-se uma ferramenta importante para o entendimento dos processos ecológicos e antrópicos que agem nos sistemas terrestres. Neste contexto, este trabalho teve como objetivo a análise do comportamento espacial da Temperatura de Superfície (Ts) e albedo na Bacia Hidrográfica do Rio Una, Ibiúna – SP, a partir de imagens do sensor MODIS dos satélites TERRA e Aqua para os meses de Janeiro e Agostos dos anos de 2004, 2008, 2012 e 2015, considerando as modificações no uso do solo e ocupação da terra e as sazonalidades climáticas. A região de estudo vem sofrendo grandes mudanças no uso e cobertura da terra em função do crescimento urbano e das áreas de cultivo temporário e reflorestamento. Por fim, gerou-se um mapa da cobertura da terra para o ano de 2013, e a partir deste, realizou-se a análise do comportamento da Temperatura de superfície e do albedo. Os resultados obtidos foram comparados também com os dados de temperatura do ar e dados pluviométricos.<br>Atmospheric phenomena studies requires understanding about the complex relationships and interactions of natural and anthropic systems. Earth surface's changes alter the energy exchange processes between surface and atmosphere, at different scales, acting in : temperature variation of surface and air, the intensity of the energy streams available on the surface and the variations on energy stored in the vegetation. Remote sensing techniques utilization for the understanding of these relationships, in a geosystems approach, helps to optimize data acquisition, refinement and accuracy of these and systemic analysis, making it an important tool for the ecological and anthropic processes understanding, that act in terrestrial systems. In this context, the research's objective was the spatial behavior analysis of surface temperature (Ts) and albedo over the watershed area of the river Una (Ibiúna-SP), utilizing MODIS sensor images, from TERRA and Aqua satellites, captured in the months of January and August of 2004, 2008, 2012 and 2015, considering the changes in land use, land occupation and climatic seasonality. The study region has suffered major changes in land use and coverage on the basis of urban growth, cultivation areas and reforestation. So, a 2013 coverage map was generated, and from this, the behavior analysis of surface temperature and albedo was made. The results obtained were compared with the data of air temperature and rainfall data.
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Kilic, Lise. "Estimation des paramètres de surface des océans et de la banquise à partir d’observations micro-ondes basses fréquences." Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS167.
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Les océans et la banquise jouent un rôle important dans le système climatique et météorologique. Une future mission satellite en micro-ondes passives basses fréquences, conçue pour observer les régions polaires est actuellement à l’étude à l’Agence Spatiale Européenne pour l’expansion du programme Copernicus. Les observations satellites en micro-ondes passives permettent une observation de la surface de la Terre par tous temps, aussi bien de jour que de nuit. Dans cette thèse, nous nous intéressons à l’estimation des paramètres de surface de l’océan et de la banquise à partir des observations satellites micro-ondes passives basses fréquences. L’objectif est de développer de nouvelles méthodes d’estimation de ces paramètres qui soient plus efficaces et adaptées à la future mission satellite micro-onde passive CIMR (Copernicus Imaging Microwave Radiometer). La première partie de la thèse traite de l’estimation des paramètres océaniques tels que la température de la surface de la mer, la salinité et la vitesse du vent océanique. La deuxième partie traite de l’estimation des paramètres de la banquise tels que la concentration en glace, l’épaisseur de neige et la température d’interface neige-glace. Enfin, avec les méthodes développées dans cette thèse les performances de la mission CIMR sont évaluées et comparées à celles des missions actuelles<br>The oceans and sea ice play an important role in the climate and weather system. A future low-frequency passive microwave satellite mission designed to observe the polar regions is currently under study at the European Space Agency for the expansion of the Copernicus programme. Passive microwave satellite observations provide all-weather observation of the Earth surface, both day and night. In this thesis, we are interested in estimating ocean and ice surface parameters from low-frequency passive microwave satellite observations. The objective is to develop new methods for estimating these parameters that are more efficient and adapted to the future passive microwave satellite mission CIMR (Copernicus Imaging Microwave Radiometer). The first part of the thesis deals with the estimation of ocean parameters such as sea surface temperature, salinity and ocean wind speed. The second part deals with the estimation of sea ice parameters such as sea ice concentration, snow depth and snow-ice interface temperature. Finally, with the methods developed in this thesis, the performances of the CIMR mission are evaluated and compared with the current missions
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Ahring, Trevor S. "Phreatophytes in southwest Kansas used as a tool for predicting hydrologic properties." Thesis, Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/1657.
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Bernard, Eric. "Les dynamiques spatio-temporelles d'un petit hydrosystème arctique : approche nivo-glaciologique dans un contexte de changement climatique contemporain (bassin du glacier Austre Lovén, Spitsberg, 79°N)." Phd thesis, Université de Franche-Comté, 2011. http://tel.archives-ouvertes.fr/tel-00910122.
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S'appuyant sur de longues missions de terrain, ce travail offre le regard quantitatif et qualitatif d'un géographe sur la dynamique nivo-glaciaire en région polaire dans un contexte de changement climatique actuel. Il s'inscrit dans le cadre du programme ANR Hydro-Sensor-FLOWS mis en oeuvre dans la mouvance de l'Année Polaire Internationale. En amont de ce programme pluridisciplinaire visant à comprendre le fonctionnement hydrologique d'un petit hydrosystème polaire il fallait adjoindre une étude plus spécifique concernant le rôle de la neige et de la glace dans l'équation hydrologique : c'est l'objet de cette thèse. Le bassin glaciaire de l'Austre Lovénbreen (10 km2, Spitsberg - 79°N) a servi de terrain d'étude dans une approche géographique à échelle locale. De nombreuses méthodes ont été testées tant sur le terrain (stations photo automatiques, carottages de la neige, DGPS et GPR) que pour l'exploitation des données acquises. Au total, ce travail suit la dynamique nivo-glaciaire pendant trois années (2008, 2009 et 2010) à partir de 15 séries de carottages en 40 points du bassin, de mesures de densité, de profils nivologiques, de bilan de masse et de suivi continu, en 20 points, de la température de l'air. Outre l'image satellite, ce travail s'appuie également sur une collection de 3 clichés journaliers acquis en 10 points du bassin. Des méthodes ont été développées pour corriger géométriquement les photos afin d'en faire des documents en projection verticale dont il est possible de tirer de l'information quantitative. Les outils de la géomatique ont permis de spatialiser l'information ponctuelle et d'établir à des pas de temps variables, par croisement des données acquises in situ, les diverses lames entrant dans l'équation hydrologique (précipitations, fonte potentielle de la neige et de la glace en relation avec les lames écoulées). Les trois années consécutives de suivi offrent des conditions très différentes qui révèlent le rôle constant et modérateur des températures et celui beaucoup plus impulsif des précipitations. Ce travail pose également le problème des mesures et de leur fiabilité dans un milieu aussi sévère et aussi impétueux que l'Arctique