Letteratura scientifica selezionata sul tema "Surface mass balance modelling"
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Articoli di riviste sul tema "Surface mass balance modelling"
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Albrecht, Olaf, Peter Jansson e Heinz Blatter. "Modelling glacier response to measured mass-balance forcing". Annals of Glaciology 31 (2000): 91–96. http://dx.doi.org/10.3189/172756400781819996.
Testo completoAbstract (sommario):
AbstractMeasurements of summer and winter mass balances have been carried out over the past 53 years on Storglaciären, northern Sweden. Repeated surveys of the glacier have resulted in several maps of surface topography as well as a map of the bed topography A new time-dependent ice flow model allows us to compare the observed surface evolution of the glacier with that computed by the model using measured mass-balance maps as input. The computed volume change compares well with the measured change: the model replicates the distribution of surface elevation to within ±10 m over 30 years of integration. On the model side, these deviations can be attributed to the low-resolution discretization of the model domain as well as to the limited accuracy of the ice rheology and omitted basal sliding. On the other hand, the uncertainties of the topography and mass-balance maps match the model uncertainties. In this sense, the experiments are a validation of both model and observations.
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Zou, Fang, Robert Tenzer, Hok Fok e Janet Nichol. "Mass Balance of the Greenland Ice Sheet from GRACE and Surface Mass Balance Modelling". Water 12, n. 7 (28 giugno 2020): 1847. http://dx.doi.org/10.3390/w12071847.
Testo completoAbstract (sommario):
The Greenland Ice Sheet (GrIS) is losing mass at a rate that represents a major contribution to global sea-level rise in recent decades. In this study, we use the Gravity Recovery and Climate Experiment (GRACE) data to retrieve the time series variations of the GrIS from April 2002 to June 2017. We also estimate the mass balance from the RACMO2.3 and ice discharge data in order to obtain a comparative analysis and cross-validation. A detailed analysis of long-term trend and seasonal and inter-annual changes in the GrIS is implemented by GRACE and surface mass balance (SMB) modeling. The results indicate a decrease of −267.77 ± 8.68 Gt/yr of the GrIS over the 16-year period. There is a rapid decline from 2002 to 2008, which accelerated from 2009 to 2012 before declining relatively slowly from 2013 to 2017. The mass change inland is significantly smaller than that detected along coastal regions, especially in the southeastern, southwestern, and northwestern regions. The mass balance estimates from GRACE and SMB minus ice discharge (SMB-D) are very consistent. The ice discharge manifests itself mostly as a long-term trend, whereas seasonal mass variations are largely attributed to surface mass processes. The GrIS mass changes are mostly attributed to mass loss during summer. Summer mass changes are highly correlated with climate changes.
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Schuler, Thomas V., Regine Hock, Miriam Jackson, Hallgeir Elvehøy, Matthias Braun, Ian Brown e Jon-Ove Hagen. "Distributed mass-balance and climate sensitivity modelling of Engabreen, Norway". Annals of Glaciology 42 (2005): 395–401. http://dx.doi.org/10.3189/172756405781812998.
Testo completoAbstract (sommario):
AbstractAssessing the impact of possible climate change on the water resources of glacierized areas requires a reliable model of the climate–glacier-mass-balance relationship. In this study, we simulate the mass-balance evolution of Engabreen, Norway, using a simple mass-balance model based on daily temperature and precipitation data from a nearby climate station. Ablation is calculated using a distributed temperature-index method including potential direct solar radiation, while accumulation is distributed linearly with elevation. The model was run for the period 1974/75–2001/02, for which annual mass-balance measurements and meteorological data are available. Parameter values were determined by a multi-criteria validation including point measurements of mass balance, mass-balance gradients and specific mass balance. The modelled results fit the observed mass balance well. Simple sensitivity experiments indicate a high sensitivity of the mass balance to temperature changes, as expected for maritime glaciers. The results suggest, further, that the mass balance of Engabreen is more sensitive to warming during summer than during winter, while precipitation changes affect almost exclusively the winter balance.
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Kneib, Marin, Amaury Dehecq, Adrien Gilbert, Auguste Basset, Evan S. Miles, Guillaume Jouvet, Bruno Jourdain et al. "Distributed surface mass balance of an avalanche-fed glacier". Cryosphere 18, n. 12 (18 dicembre 2024): 5965–83. https://doi.org/10.5194/tc-18-5965-2024.
Testo completoAbstract (sommario):
Abstract. Local snow redistribution processes such as avalanches can considerably impact the spatial variability of accumulation on glaciers. However, this spatial variability is difficult to quantify with traditional surface mass balance measurements or geodetic observations. Here, we leverage high-quality and high-resolution surface velocity and elevation change maps for the period 2012–2021 from Pléiades stereo images and ice thickness measurements of Argentière Glacier (France) to invert for its distributed surface mass balance. Three inversions are conducted using three different ice thickness modelling approaches, two of which are constrained by observations. The inversions all show very good agreement between inverted surface mass balance and in situ measurements (RMSE between 0.50 and 0.96 mw.e.yr-1 for the 11-year average). The detected spatial variability in surface mass balance is consistent between the modelling approaches and much higher than what is predicted from an enhanced-temperature-index model calibrated with measurements from a dense network of stakes. In particular, we find high accumulation rates at the base of steep headwalls on the left-hand side of the glacier, likely related to avalanche deposits at these locations. We calculate distributed precipitation correction factors to reconcile the outputs from the enhanced-temperature-index model with the inverted surface mass balance data. These correction factors agree with the outputs of a parametrisation of snow redistribution by avalanching, indicating an additional 60 % mass input relative to the accumulation from solid precipitation at these specific locations, which was equivalent to an additional 20 % mass accumulation at the scale of Argentière Glacier without its two smaller tributaries. Using these correction factors in a forward-modelling exercise, we show that explicitly accounting for avalanches leads to twice more ice being conserved in the Argentière catchment by 2100 in an RCP 4.5 climate scenario and to a considerably different ice thickness distribution. Our results highlight the need to better account for such spatially variable accumulation processes in glacio-hydrological models.
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Hubbard, Alun, Ian Willis, Martin Sharp, Douglas Mair, Peter Nienow, Bryn Hubbard e Heinz Blatter. "Glacier mass-balance determination by remote sensing and high-resolution modelling". Journal of Glaciology 46, n. 154 (2000): 491–98. http://dx.doi.org/10.3189/172756500781833016.
Testo completoAbstract (sommario):
AbstractAn indirect methodology for determining the distribution of mass balance at high spatial resolution using remote sensing and ice-flow modelling is presented. The method, based on the mass-continuity equation, requires two datasets collected over the desired monitoring interval: (i) the spatial pattern of glacier surface-elevation change, and (ii) the mass-flux divergence field. At Haut Glacier d’Arolla, Valais, Switzerland, the mass-balance distribution between September 1992 and September 1993 is calculated at 20 m resolution from the difference between the pattern of surface-elevation change derived from analytical photogrammetry and the mass-flux divergence field determined from three-dimensional, numerical flow modelling constrained by surface-velocity measurements. The resultant pattern of mass balance is almost totally negative, showing a strong dependence on elevation, but with large localized departures. The computed distribution of mass balance compares well (R2 = 0.91) with mass-balance measurements made at stakes installed along the glacier centre line over the same period. Despite the highly optimized nature of the flow-modelling effort employed in this study, the good agreement indicates the potential this method has as a strategy for deriving high spatial and temporal-resolution estimates of mass balance.
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Vincent, Christian, Diego Cusicanqui, Bruno Jourdain, Olivier Laarman, Delphine Six, Adrien Gilbert, Andrea Walpersdorf et al. "Geodetic point surface mass balances: a new approach to determine point surface mass balances on glaciers from remote sensing measurements". Cryosphere 15, n. 3 (10 marzo 2021): 1259–76. http://dx.doi.org/10.5194/tc-15-1259-2021.
Testo completoAbstract (sommario):
Abstract. Mass balance observations are very useful to assess climate change in different regions of the world. As opposed to glacier-wide mass balances which are influenced by the dynamic response of each glacier, point mass balances provide a direct climatic signal that depends on surface accumulation and ablation only. Unfortunately, major efforts are required to conduct in situ measurements on glaciers. Here, we propose a new approach that determines point surface mass balances from remote sensing observations. We call this balance the geodetic point surface mass balance. From observations and modelling performed on the Argentière and Mer de Glace glaciers over the last decade, we show that the vertical ice flow velocity changes are small in areas of low bedrock slope. Therefore, assuming constant vertical velocities in time for such areas and provided that the vertical velocities have been measured for at least 1 year in the past, our method can be used to reconstruct annual point surface mass balances from surface elevations and horizontal velocities alone. We demonstrate that the annual point surface mass balances can be reconstructed with an accuracy of about 0.3 m of water equivalent per year (m w.e. a−1) using the vertical velocities observed over the previous years and data from unmanned aerial vehicle images. Given the recent improvements of satellite sensors, it should be possible to apply this method to high-spatial-resolution satellite images as well.
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Huintjes, E., H. Li, T. Sauter, Z. Li e C. Schneider. "Degree-day modelling of the surface mass balance of Urumqi Glacier No. 1, Tian Shan, China". Cryosphere Discussions 4, n. 1 (3 marzo 2010): 207–32. http://dx.doi.org/10.5194/tcd-4-207-2010.
Testo completoAbstract (sommario):
Abstract. A distributed temperature-index melt model including potential shortwave radiation is used to calculate annual mean surface mass balance and the spatial distribution of melt rates on the east branch of Urumqi Glacier No. 1, north-western China. The lack of continuous datasets at higher temporal resolution for various climate variables suggests the application of a degree-day model with only few required input variables. The model is calibrated for a six day period in July 2007, for which daily mass balance measurements and meteorological data are available. Based on point measurements of mass balance, parameter values are optimised running a constrained multivariable function using the simplex search method. To evaluate the model performance, annual mass balances for the period 1987/88–2004/05 are calculated using NCEP/NCAR-Reanalysis data. The modelled values fit the observed mass balance with a correlation of 0.98 and an RMSE of 332 mm w.e. Furthermore, the calculated spatial distribution of melt rates shows an improvement in small-scale variations compared to the simple degree-day approach.
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Machguth, Horst, Frank Paul, Martin Hoelzle e Wilfried Haeberli. "Distributed glacier mass-balance modelling as an important component of modern multi-level glacier monitoring". Annals of Glaciology 43 (2006): 335–43. http://dx.doi.org/10.3189/172756406781812285.
Testo completoAbstract (sommario):
AbstractModern concepts of worldwide glacier monitoring include numerical models for (1) interconnecting the different levels of observations (local mass balance, representative length change, glacier inventories for global coverage) and (2) extrapolations in space (coupling with climate models) and time (backward and forward). In this context, one important new tool is distributed mass-balance modelling in complex mountain topography. This approach builds on simplified energy-balance models and can be applied for investigating the spatio-temporal representativity of the few mass-balance measurements, for estimating balance values at the tongue of unmeasured glaciers in order to derive long-term average balance values from a great number of glaciers with known length change, and for assessing special effects such as the influence of Sahara dust falls on the albedo and mass balance or autocorrelation effects due to surface darkening of glaciers with strongly negative balances. Experience from first model runs in the Swiss Alps and from applications to the extreme conditions in summer 2003 provides evidence about the usefulness of this approach for glacier monitoring and analysis of glacier changes in high-mountain regions. The main difficulties concern the spatial variability of the input parameters (e.g. precipitation, snow cover and surface albedo) and the uncertainties in the parameterizations of the components of the energy balance. Field measurements remain essential to tie the models to real ground conditions.
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Krapp, Mario, Alexander Robinson e Andrey Ganopolski. "SEMIC: an efficient surface energy and mass balance model applied to the Greenland ice sheet". Cryosphere 11, n. 4 (3 luglio 2017): 1519–35. http://dx.doi.org/10.5194/tc-11-1519-2017.
Testo completoAbstract (sommario):
Abstract. We present SEMIC, a Surface Energy and Mass balance model of Intermediate Complexity for snow- and ice-covered surfaces such as the Greenland ice sheet. SEMIC is fast enough for glacial cycle applications, making it a suitable replacement for simpler methods such as the positive degree day (PDD) method often used in ice sheet modelling. Our model explicitly calculates the main processes involved in the surface energy and mass balance, while maintaining a simple interface and requiring minimal data input to drive it. In this novel approach, we parameterise diurnal temperature variations in order to more realistically capture the daily thaw–freeze cycles that characterise the ice sheet mass balance. We show how to derive optimal model parameters for SEMIC specifically to reproduce surface characteristics and day-to-day variations similar to the regional climate model MAR (Modèle Atmosphérique Régional, version 2) and its incorporated multilayer snowpack model SISVAT (Soil Ice Snow Vegetation Atmosphere Transfer). A validation test shows that SEMIC simulates future changes in surface temperature and surface mass balance in good agreement with the more sophisticated multilayer snowpack model SISVAT included in MAR. With this paper, we present a physically based surface model to the ice sheet modelling community that is general enough to be used with in situ observations, climate model, or reanalysis data, and that is at the same time computationally fast enough for long-term integrations, such as glacial cycles or future climate change scenarios.
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Willen, Matthias O., Martin Horwath, Eric Buchta, Mirko Scheinert, Veit Helm, Bernd Uebbing e Jürgen Kusche. "Globally consistent estimates of high-resolution Antarctic ice mass balance and spatially resolved glacial isostatic adjustment". Cryosphere 18, n. 2 (20 febbraio 2024): 775–90. http://dx.doi.org/10.5194/tc-18-775-2024.
Testo completoAbstract (sommario):
Abstract. A detailed understanding of how the Antarctic ice sheet (AIS) responds to a warming climate is needed because it will most likely increase the rate of global mean sea level rise. Time-variable satellite gravimetry, realized by the Gravity Recovery and Climate Experiment (GRACE) and Gravity Recovery and Climate Experiment Follow-On (GRACE-FO) missions, is directly sensitive to AIS mass changes. However, gravimetric mass balances are subject to two major limitations. First, the usual correction of the glacial isostatic adjustment (GIA) effect by modelling results is a dominant source of uncertainty. Second, satellite gravimetry allows for a resolution of a few hundred kilometres only, which is insufficient to thoroughly explore causes of AIS imbalance. We have overcome both limitations by the first global inversion of data from GRACE and GRACE-FO, satellite altimetry (CryoSat-2), regional climate modelling (RACMO2), and firn densification modelling (IMAU-FDM). The inversion spatially resolves GIA in Antarctica independently from GIA modelling jointly with changes of ice mass and firn air content at 50 km resolution. We find an AIS mass balance of −144 ± 27 Gt a−1 from January 2011 to December 2020. This estimate is the same, within uncertainties, as the statistical analysis of 23 different mass balances evaluated in the Ice sheet Mass Balance Inter-comparison Exercise (IMBIE; Otosaka et al., 2023b). The co-estimated GIA corresponds to an integrated mass effect of 86 ± 21 Gt a−1 over Antarctica, and it fits better with global navigation satellite system (GNSS) results than other GIA predictions. From propagating covariances to integrals, we find a correlation coefficient of −0.97 between the AIS mass balance and the GIA estimate. Sensitivity tests with alternative input data sets lead to results within assessed uncertainties.
Tesi sul tema "Surface mass balance modelling"
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Marsh, Oliver John. "Ice dynamics and mass balance in the grounding zone of outlet glaciers in the Transantarctic Mountains". Thesis, University of Canterbury. Gateway Antarctica, 2013. http://hdl.handle.net/10092/8722.
Testo completoAbstract (sommario):
The Antarctic grounding zone has a disproportionately large effect on glacier dynamics and ice sheet stability relative to its size but remains poorly characterised across much of the continent. Accurate ice velocity and thickness information is needed in the grounding zone to determine glacier outflow and establish to what extent changing ocean and atmospheric conditions are affecting the mass balance of individual glacier catchments.
This thesis describes new satellite remote sensing techniques for measuring ice velocity and ice thickness, validated using ground measurements collected on the Beardmore, Skelton and Darwin Glaciers and applied to other Transantarctic Mountain
outlet glaciers to determine ice discharge. Outlet glaciers in the Transantarctic Mountains provide an important link between the East and West Antarctic Ice Sheets but remain inadequately studied. While long-term velocities in this region
are shown here to be stable, instantaneous velocities are sensitive to stresses induced by ocean tides, with fluctuations of up to 50% of the mean observed in GPS measurements. The potential error induced in averaged satellite velocity measurements due to these effects is shown to be resolvable above background noise in the grounding zone but to decrease rapidly upstream. Using a new inverse finite-element modelling
approach based on regularization of the elastic-plate bending equations, tidal flexure information from differential InSAR is used to calculate ice stiffness and infer thickness in the grounding zone. This technique is shown to be successful at reproducing the thickness distribution for the Beardmore Glacier, eliminating current issues in the calculation of thickness from freeboard close to the grounding line where ice is not in hydrostatic equilibrium. Modelled thickness agrees to within 10% of ground penetrating radar measurements. Calibrated freeboard measurements and tide-free velocities in the grounding zones of glaciers in the western Ross Sea are used to calculate grounding zone basal melt rates, with values between 1.4 and 11.8 m/a⁻¹ in this region. While strongly dependent on grounding line ice thickness and velocity, melt rates show no latitudinal trend between glaciers, although detailed error analysis highlights the need for much improved estimates of firn density distribution in regions of variable accumulation such as the Transantarctic Mountains.
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Agosta, Cécile. "Evolution du bilan de masse de surface Antarctique par régionalisation physique et contribution aux variations du niveau des mers". Thesis, Grenoble, 2012. http://www.theses.fr/2012GRENU023/document.
Testo completoAbstract (sommario):
Le Bilan de Masse de Surface (BMS, c'est-à-dire les précipitations de neige auxquelles est retranchée l'ablation par sublimation, ruissellement ou érosion) de la calotte polaire Antarctique représente une contribution majeure et encore mal connue à l'évolution actuelle du niveau des mers. Le stockage d'eau douce par accumulation de neige sur la calotte posée est supposé s'intensifier au cours du 21eme siècle, modérant l'élévation du niveau des mers et modifiant la dynamique glaciaire. Les trois-quarts du bilan de masse de surface Antarctique sont concentrés au dessous de 2000 m d'altitude alors que cette zone ne représente que 40% de la surface de la calotte posée. Les précipitations orographiques sont une contribution majeure à l'accumulation dans cette région, il est donc crucial d'estimer précisément ce terme. La modélisation de ce processus est fortement dépendant de la résolution des modèles, car les pentes de la calotte influencent l'intensité des précipitations orographiques. La sublimation et la fonte de la neige sont eux aussi fortement dépendant de l'élévation. Bien qu'ils contribuent actuellement peu au bilan de masse de surface de l'Antarctique, ils sont susceptibles de subir des changements importants au cours des prochains siècles. Les modèles atmosphériques de climat, globaux ou régionaux, ne peuvent pas atteindre une résolution allant au delà de 40 km sur l'Antarctique pour des simulations à l'échelle du siècle du fait de coûts de calcul importants. A ces résolutions, la topographie des zones côtières Antarctique n'est pas correctement représentée. C'est pourquoi nous avons développé le modèle de régionalisation SMHiL (Surface Mass balance High-resolution downscaLing) qui permet d'estimer les composantes du bilan de masse de surface Antarctique à haute résolution (~15 km) à partir de champs atmosphériques de plus grande échelle. Nous calculons l'effet de la topographie fine sur les précipitations orographiques et sur les processus de couche limite menant à la sublimation, la fonte et le regel. SMHiL est validé pour la période actuelle à partir d'un jeu de données inédit constitué de plus de 2700 observations de qualité contrôlée. Cependant, les observations représentatives du BMS de la zone côtière Antarctique y sont sous-représentées. Dans ce contexte, nous montrons que la ligne de balise mise en place par l'observatoire GLACIOCLIM-SAMBA en bordure de calotte constitue une référence pour estimer les performances des modèles. Enfin, nous utilisons SMHiL à l'aval du modèle de circulation générale LMDZ4 pour évaluer les variations de BMS au cours du 21eme et du 22eme siècles. Le BMS à haute résolution est significativement différent de celui de LMDZ4 et est plus proche du BMS observé pour la période actuelle. Les résultats suggèrent que les précédentes estimations d'augmentation du BMS au cours du prochain siècle étaient sous-estimées de près de 30% par LMDZ4. Les changements de BMS à faible élévation résulteront d'une compétition entre l'augmentation d'accumulation de neige et de ruissellement. SMHiL est un outil destiné à être appliqué à l'aval d'autres modèles de climat, globaux ou régionaux, pour une meilleure estimation des variations futures du niveau des mersThe Antarctic Surface Mass Balance (SMB, i.e. the snow accumulation from which we subtract ablation by sublimation, run-off or erosion) is a major yet badly known contribution to changes in the present-day sea level. Water storage by snow accumulation on the Antarctic continent is expected to increase in the 21st century, which would moderate the rise in sea level and impact the ice dynamic response of the ice sheet. Three-quarters of the Antarctic SMB are concentrated below 2000 m above sea level whereas this area represents only 40% of the grounded ice sheet area. Orographic precipitation is a major contributor to snow accumulation in this region, which is why a better estimation of this term is important. The representation of this process by models depends to a great extent on the resolution of the model, since precipitation amounts depend on the ice sheet slopes. Sublimation and snowmelt also depend on elevation, and although they are presently minor contributors to the Antarctic SMB, their role is expected to become more important in the coming centuries. Global and regional atmospheric climate models are unable to achieve a 40-km resolution over Antarctica at a century time scale, due to their computing cost. At this resolution, the Antarctic coastal area is still badly represented. This is why we developed the downscaling model SMHiL (Surface mass balance high-resolution downscaling) to estimate the Antarctic SMB components at a high resolution (~15 km) from large-scale atmospheric forcings. We computed the impact of the high-resolution topography on orographic precipitation amounts and the boundary layer processes that lead to sublimation, melting and refreezing. SMHiL has been validated for the present period with a dataset composed of more than 2700 quality-controlled observations. However, very few of these observations are representative of the Antarctic coastal area. In this context, we show that the GLACIOCLIM-SAMBA stake lines located on the ice sheet coast-to-plateau area is an appropriate reference to evaluate model performance. Finally, we used SMHiL to estimate the SMB changes during the 21st and 22nd centuries, by downscaling the atmospheric global climate model LMDZ4. The high-resolution SMB is significantly different from the SMB given by LMDZ4 and is closer to the observed one for the present period. Our results suggest that previous studies using the LMDZ4 models underestimated the future increase in SMB in Antarctica by about 30%. Future changes in the Antarctic SMB at low elevations will result from the conflict between higher snow accumulation and runoff. The downscaling model is a powerful tool that can be applied to climate models for a better assessment of a future rise in sea level
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Callens, Denis. "Impact of improved basal and surface boundary conditions on the mass balance of the Sr Rondane Mountains glacial system, Dronning Maud Land, Antarctica". Doctoral thesis, Universite Libre de Bruxelles, 2014. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209217.
Testo completoAbstract (sommario):
Mass changes of polar ice sheets have an important societal impact, because they affect global sea level. Estimating the current mass budget of ice sheets is equivalent to determining the balance between the surface mass gain through precipitation and the outflow across the grounding line. In Antarctica, the latter is mainly governed by oceanic processes and outlet glacier dynamics.In this thesis, we assess the mass balance of a part of eastern DronningMaud Land via an input/output method. Input is given by recent surface accumulation estimations of the whole drainage basin. The outflow at the grounding line is determined from the radar data of a recent airborne survey and satellite-based velocities using a flow model of combined plug flow and simple shear. We estimate the regional mass balance in this area to be between 1.88±8.50 and 3.78±3.32 Gt a−1 depending on the surface mass balance (SMB) dataset used. This study also reveals that the plug flow assumption is acceptable at the grounding line of ice streams.
The mass balance of drainage basins is governed by the dynamics of their outlet glaciers and more specifically the flow conditions at the grounding line. Thanks to an airborne radar survey we define the bed properties close to the grounding line of the West Ragnhild Glacier (WRG) in the Sør Rondane Mountains. Geometry and reflectivity analyses reveal that the bed of the last 65 km upstream of the grounding line is sediment covered and saturated with water. This setting promotes the dominance of basal motion leading to a change in the flow regime: in the interior flow is governed by internal deformation while its relative importance decreases to become driven by basal sliding.
Subsequently we present the results of the reconstruction of the SMB across an ice rise through radar data and inverse modelling. The analysis demonstrates that atmospheric circulation was stable during the last millennium. Ice rises induce an orographic uplift of the atmospheric flow and therefore influence the pattern of the SMB across them, resulting in an asymmetric SMB distribution. Since the geometry of the internal reflection horizons observed in radar data depends on the SMB pattern, the asymmetry observed in radar layers reveals the trajectories of air masses at the time of deposit. We present an original and robust method to quantify this SMB distribution. Combining shallow and deep radar layers, SMB across Derwael Ice Rise is reconstructed. Two methods are employed as a function of the depth of the layers: i.e. the shallow layer approximation for the surface radar layers and an optimization technique based on an ice flow model for the deeper ones. Both methods produce similar results. We identify a difference in SMB magnitude of 2.5 between the flanks and the ice rise divide, as well as a shift of ≈4 km between the SMB maximum and the crest. Across the ice rise, SMB exhibits a very large variability, ranging from 0.3 to 0.9 mw.e. a−1. This anomaly is robust in time.
Finally we draw a comprehensive description of the Sør Rondane Mountains sector. The glacial system is close to the equilibrium and seems stable but evidences suggest that it is a fragile equilibrium. The proximity of the open ocean certainly favours the interaction between warm water and the ice shelf cavity conducting to potential important melting. The thinning associated with this melting can detach the ice shelf from pinning points. This will reduce the buttressing from the ice shelf, outlet glaciers will accelerate and mass transfer toward the ocean will increase. Therefore, the future of Antarctic Ice Sheet directly depends on the changes affecting its boundaries and assessing the sensitivity of the ice sheets is essential to quantify and anticipate the future variation of mass balance.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Guinaldo, Thibault. "Paramétrisation de la dynamique lacustre dans un modèle de surface couplé pour une application à la prévision hydrologique à l’échelle globale". Thesis, Toulouse, INPT, 2020. http://www.theses.fr/2020INPT0125.
Testo completoAbstract (sommario):
L'hydrologie continentale s'intéresse à tous les aspects du cycle de l'eau des terres émergées et représente les flux de masse d'eau qui sont échangées. Que ce soit dans le sous-sol, au sein des lacs ou dans le brassage continu des torrents, l'eau et les processus hydrologiques associés entretiennent un lien direct avec la dynamique atmosphérique et la variabilité climatique. La représentation, à l'échelle globale, de ces processus hydrologiques s'appuie sur des techniques de modélisation qui, au CNRM, passent par un système couplé composé du modèle de surface ISBA et du modèle de routage en rivière CTRIP. Ces dernières années, les progrès réalisés sur les paramétrisations existantes et la représentation des nouveaux processus dans ISBA comme dans CTRIP ont abouti à une nette amélioration des performances de ce système pour des applications hydrologiques régionales ou globales couplées avec un modèle de climat. Dans la continuité de ces efforts, l'objectif principal de cette thèse est de développer une paramétrisation dynamique des lacs pour intégrer leur bilan de masse dans le modèle global CTRIP à 1/12°. Par ailleurs, le modèle développé, MLake, propose un diagnostic sur le marnage des lacs afin de permettre le suivi du niveau d'eau basé sur des mesures satellitaires. Bénéficiant d'un réseau de mesures dense et de forçages climatiques à haute résolution, le bassin versant du Rhône a été choisi pour évaluer localement MLake sur la période 1960-2016. Les résultats sur trois stations de jaugeages montrent une progression nette des performances de CTRIP dans la simulation des débits du Rhône aboutissant à un lissage des hydrographes qui se caractérise par un écrêtement des débits de crues et un soutien à l'étiage. Par ailleurs, la confrontation du diagnostic sur les niveaux d'eau du Léman avec des mesures locales révèle une capacité du modèle à suivre les cycle annuels et inter-annuels du marnage. Une deuxième évaluation s'est ensuite portée à l'échelle globale pour confirmer le comportement du modèle dans des conditions hydroclimatiques contrastées. Cette évaluation confirme la capacité du modèle à simuler des débits réalistes mais révèle la perturbation importante du cycle hydrologique naturel par l'anthropisation. Enfin les résultats préliminaires d'une simulation globale démontre l'intérêt d'utiliser MLake avec une amélioration systématique des scores dans les zones de grande densité lacustre. Ainsi, 45% des stations évaluées, principalement dans les régions arctiques, présentent une amélioration des scores statistiques. Enfin, cette étude engage une réflexion sur les perspectives d'améliorations du modèle, notamment la mise en place d'une bathymétrie de lac à l'échelle globale, en vue d'un couplage avec un modèle de climat et de l'utilisation des données de la future mission spatiale SWOTThe water cycle encompasses the main processes related to mass fluxes that influence the atmosphere and climate variability. More specifically, continental hydrology refers to the water transfer occurring at the land surface and sub-surface. Modelling is one of the main methods used for the representation of these processes at regional to global scales. The land surface model system used in this thesis is composed of the ISBA land surface model coupled to the river routing model TRIP that combines the CNRM’s latest developments for use in stand-alone hydrological applications or coupled to a climate model. This PhD is focused on the development and evaluation of lake mass-balance dynamics and water level diagnostics using a new non-calibrated model called MLake which has been incorporated into the 1/12° version of the CTRIP model. Simulated river flows forced by high resolution hydrometeorological forcings are evaluated for the Rhone river basin against in situ observations coming from three river gauges over the period 1960-2016. Results reveal the positive contribution of MLake in simulating Rhone discharge and in representing the lake buffer effects on peak discharge. Moreover, the evaluation of the simulated and observed water level variations show the ability of MLake to reproduce the natural seasonal and interannual cycles. Based on the same framework, a final evaluation was conducted in order to assess the value of the non-calibrated MLake model for global hydrological applications. The results confirmed the capability of the model to simulate realistic river discharges worldwide. At 45% of the river gauge stations, which are mostly located within regions of high lake density, the new model resulted in improved simulated river discharge. The results also highlighted the strong effect of anthropization on the alterations of river dynamics, and the need for a global representation of human-impacted flows in the model. This study has lead to several future perspectives, such as the incorporation of a parametrization of lake hypsometry for use at global scale. The implementation of such developments will improve the representation of vertical water dynamics and facilitate both the coupling of MLake within the CNRM earth system model framework and the future spatial mission SWOT for improved future global hydrological and water resource projections
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Hoang, Thi Khanh Dieu. "A numerical approach to understanding rates of ice sheet build-up during the Quaternary". Electronic Thesis or Diss., université Paris-Saclay, 2025. http://www.theses.fr/2025UPASJ002.
Testo completoAbstract (sommario):
Au cours du Quaternaire (depuis 2.6 Ma), les calottes glaciaires connaissent différents épisodes d'avancée-retrait correspondant aux cycles glaciaires-interglaciaires. L'étude de ces événements épisodiques permet de mieux comprendre les mécanismes à l'origine de l'évolution de la Terre et d'améliorer les prévisions dans le contexte du réchauffement climatique actuel.La simulation des interactions entre les calottes polaires et le climat sur des échelles de temps aussi longues nécessite des approches de modélisation numérique qui représentent suffisamment le système réel tout en maintenant des coûts de calcul faibles. Dans la première partie de cette thèse, j'utilise un modèle système terre système terrestre de complexité intermédiaire (iLOVECLIM) couplé au modèle 3D de calotte polaires GRISLI pour simuler l'avancée abrupte de la calotte glaciaire au début du dernier cycle glaciaire (120-115 kaBP). Les résultats indiquent que les débuts de glaciation ne peuvent pas être expliqués uniquement par la théorie astronomique (en résponse aux forçages orbitaux). Les rôles de la biosphère et de l'océan par le biais de différents mécanismes de rétroaction doivent être inclus pour expliquer la localisation et l'étendue de l'avancée de la calotte glaciaire. De plus, une simulation appropriée du processus d'accumulation de la calotte glaciaire est essentielle pour obtenir des résultats corrects.Dans la deuxième partie de la thèse, j'étudie les comportements d'un modèle de neige multicouche BESSI afin de fournir une simulation de bilan de masse de surface (SMB) davantage basée sur la physique pour iLOVECLIM-GRISLI. Le modèle de neige présente de bons résultats par rapport à un modèle climatique régional MAR de pointe pour le climat actuel dans différentes conditions de calotte glaciaire. Pour le dernier interglaciaire (130-116 kaBP), BESSI forcé par iLOVECLIM montre une plus grande sensibilité aux forçages climatiques que la paramétrisation SMB existante d'iLOVECLIM-GRISLI. En outre, l'évolution du SMB simulée par BESSI-iLOVECLIM se situe également dans une fourchette acceptable par rapport à d'autres études. Cependant, comme ce modèle de neige est davantage fondé sur la physique que la paramétrisation existante, l'influence des biais d'iLOVECLIM est plus importante pour BESSI, ce qui nuit à ses performances. Moyennant des travaux à venir sur la correction de biais et la méthode de couplage, mon étude ouvre la voie à l'utilisation de BESSI dans le cadre du couplage entre le modèle de climat iLOVECLIM et le modèle de calottes glaciaires GRISLIDuring the Quaternary (since 2.6 Ma), ice sheets experience different advance-retreat episodes corresponding to glacial-interglacial cycles. Studying these episodic events provides a better understanding of the mechanisms behind the Earth's evolution, improving the future projection for the current global warming.Simulating ice sheet-climate interactions for long timescales requires numerical modeling approaches that sufficiently represent the real system while maintaining low computational costs. In the first part of this thesis, I utilize an Earth System of Intermediate Complexity (iLOVECLIM) coupled to the 3D ice sheet model GRISLI to simulate the abrupt ice sheet advance during the beginning of the last glacial cycle (120-115 kaBP). The results indicate glacial inceptions cannot be explained solely by the astronomical theory (the influence of orbital forcings). The roles of the biosphere and ocean through different feedback mechanisms must be included to explain the location and extent of ice sheet advance. Also, an appropriate simulation of the ice sheet accumulation process is essential to obtain results consistent with the paleo records.In the second part of the thesis, I investigate the behaviors of a multi-layer snow model BESSI to provide a more physics-based surface mass balance (SMB) simulation for iLOVECLIM-GRISLI. The snow model exhibits good results compared to a state-of-the-art Regional Climate Model MAR for the present-day climate under different ice sheet conditions. For the Last Interglacial (130-116 kaBP), BESSI forced by iLOVECLIM shows higher sensitivity to the climate forcings than the existing SMB parameterization of iLOVECLIM-GRISLI. Additionally, the SMB evolution simulated by BESSI-iLOVECLIM is also in an acceptable range compared to other studies. However, since this snow model is more physics-based than the existing parameterization, the influence of biases of iLOVECLIM is more significant for BESSI, hampering its performance. With further work to come on bias correction and the coupling method, my study paves the way for the use of BESSI in the coupling between the iLOVECLIM climate model and the GRISLI ice sheet model
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Labadz, Martin. "A catchment modelling approach integrating surface and groundwater processes, land use and distribution of nutrients : Elimbah Creek, southeast Queensland". Thesis, Queensland University of Technology, 2012. https://eprints.qut.edu.au/60017/1/Martin_Labadz_Thesis.pdf.
Testo completoAbstract (sommario):
As the world’s population is growing, so is the demand for agricultural products. However, natural nitrogen (N) fixation and phosphorus (P) availability cannot sustain the rising agricultural production, thus, the application of N and P fertilisers as additional nutrient sources is common. It is those anthropogenic activities that can contribute high amounts of organic and inorganic nutrients to both surface and groundwaters resulting in degradation of water quality and a possible reduction of aquatic life. In addition, runoff and sewage from urban and residential areas can contain high amounts of inorganic and organic nutrients which may also affect water quality. For example, blooms of the cyanobacterium Lyngbya majuscula along the coastline of southeast Queensland are an indicator of at least short term decreases of water quality. Although Australian catchments, including those with intensive forms of land use, show in general a low export of nutrients compared to North American and European catchments, certain land use practices may still have a detrimental effect on the coastal environment.
Numerous studies are reported on nutrient cycling and associated processes on a catchment scale in the Northern Hemisphere. Comparable studies in Australia, in particular in subtropical regions are, however, limited and there is a paucity in the data, in particular for inorganic and organic forms of nitrogen and phosphorus; these nutrients are important limiting factors in surface waters to promote algal blooms. Therefore, the monitoring of N and P and understanding the sources and pathways of these nutrients within a catchment is important in coastal zone management. Although Australia is the driest continent, in subtropical regions such as southeast Queensland, rainfall patterns have a significant effect on runoff and thus the nutrient cycle at a catchment scale. Increasingly, these rainfall patterns are becoming variable. The monitoring of these climatic conditions and the hydrological response of agricultural catchments is therefore also important to reduce the anthropogenic effects on surface and groundwater quality.
This study consists of an integrated hydrological–hydrochemical approach that assesses N and P in an environment with multiple land uses. The main aim is to determine the nutrient cycle within a representative coastal catchment in southeast Queensland, the Elimbah Creek catchment. In particular, the investigation confirms the influence associated with forestry and agriculture on N and P forms, sources, distribution and fate in the surface and groundwaters of this subtropical setting. In addition, the study determines whether N and P are subject to transport into the adjacent estuary and thus into the marine environment; also considered is the effect of local topography, soils and geology on N and P sources and distribution. The thesis is structured on four components individually reported.
The first paper determines the controls of catchment settings and processes on stream water, riverbank sediment, and shallow groundwater N and P concentrations, in particular during the extended dry conditions that were encountered during the study. Temporal and spatial factors such as seasonal changes, soil character, land use and catchment morphology are considered as well as their effect on controls over distributions of N and P in surface waters and associated groundwater. A total number of 30 surface and 13 shallow groundwater sampling sites were established throughout the catchment to represent dominant soil types and the land use upstream of each sampling location. Sampling comprises five rounds and was conducted over one year between October 2008 and November 2009. Surface water and groundwater samples were analysed for all major dissolved inorganic forms of N and for total N. Phosphorus was determined in the form of dissolved reactive P (predominantly orthophosphate) and total P. In addition, extracts of stream bank sediments and soil grab samples were analysed for these N and P species. Findings show that major storm events, in particular after long periods of drought conditions, are the driving force of N cycling. This is expressed by higher inorganic N concentrations in the agricultural subcatchment compared to the forested subcatchment. Nitrate N is the dominant inorganic form of N in both the surface and groundwaters and values are significantly higher in the groundwaters. Concentrations in the surface water range from 0.03 to 0.34 mg N L..1; organic N concentrations are considerably higher (average range: 0.33 to 0.85 mg N L..1), in particular in the forested subcatchment. Average NO3-N in the groundwater has a range of 0.39 to 2.08 mg N L..1, and organic N averages between 0.07 and 0.3 mg N L..1. The stream bank sediments are dominated by organic N (range: 0.53 to 0.65 mg N L..1), and the dominant inorganic form of N is NH4-N with values ranging between 0.38 and 0.41 mg N L..1. Topography and soils, however, were not to have a significant effect on N and P concentrations in waters. Detectable phosphorus in the surface and groundwaters of the catchment is limited to several locations typically in the proximity of areas with intensive animal use; in soil and sediments, P is negligible.
In the second paper, the stable isotopes of N (14N/15N) and H2O (16O/18O and 2H/H) in surface and groundwaters are used to identify sources of dissolved inorganic and organic N in these waters, and to determine their pathways within the catchment; specific emphasis is placed on the relation of forestry and agriculture. Forestry is predominantly concentrated in the northern subcatchment (Beerburrum Creek) while agriculture is mainly found in the southern subcatchment (Six Mile Creek). Results show that agriculture (horticulture, crops, grazing) is the main source of inorganic N in the surface waters of the agricultural subcatchment, and their isotopic signature shows a close link to evaporation processes that may occur during water storage in farm dams that are used for irrigation. Groundwaters are subject to denitrification processes that may result in reduced dissolved inorganic N concentrations. Soil organic matter delivers most of the inorganic N to the surface water in the forested subcatchment. Here, precipitation and subsequently runoff is the main source of the surface waters. Groundwater in this area is affected by agricultural processes. The findings also show that the catchment can attenuate the effects of anthropogenic land use on surface water quality. Riparian strips of natural remnant vegetation, commonly 50 to 100 m in width, act as buffer zones along the drainage lines in the catchment and remove inorganic N from the soil water before it enters the creek. These riparian buffer zones are common in most agricultural catchments of southeast Queensland and are indicated to reduce the impact of agriculture on stream water quality and subsequently on the estuary and marine environments. This reduction is expressed by a significant decrease in DIN concentrations from 1.6 mg N L..1 to 0.09 mg N L..1, and a decrease in the �15N signatures from upstream surface water locations downstream to the outlet of the agricultural subcatchment. Further testing is, however, necessary to confirm these processes. Most importantly, the amount of N that is transported to the adjacent estuary is shown to be negligible.
The third and fourth components of the thesis use a hydrological catchment model approach to determine the water balance of the Elimbah Creek catchment. The model is then used to simulate the effects of land use on the water balance and nutrient loads of the study area. The tool that is used is the internationally widely applied Soil and Water Assessment Tool (SWAT). Knowledge about the water cycle of a catchment is imperative in nutrient studies as processes such as rainfall, surface runoff, soil infiltration and routing of water through the drainage system are the driving forces of the catchment nutrient cycle. Long-term information about discharge volumes of the creeks and rivers do, however, not exist for a number of agricultural catchments in southeast Queensland, and such information is necessary to calibrate and validate numerical models. Therefore, a two-step modelling approach was used to calibrate and validate parameters values from a near-by gauged reference catchment as starting values for the ungauged Elimbah Creek catchment. Transposing monthly calibrated and validated parameter values from the reference catchment to the ungauged catchment significantly improved model performance showing that the hydrological model of the catchment of interest is a strong predictor of the water water balance. The model efficiency coefficient EF shows that 94% of the simulated discharge matches the observed flow whereas only 54% of the observed streamflow was simulated by the SWAT model prior to using the validated values from the reference catchment. In addition, the hydrological model confirmed that total surface runoff contributes the majority of flow to the surface water in the catchment (65%). Only a small proportion of the water in the creek is contributed by total base-flow (35%). This finding supports the results of the stable isotopes 16O/18O and 2H/H, which show the main source of water in the creeks is either from local precipitation or irrigation waters delivered by surface runoff; a contribution from the groundwater (baseflow) to the creeks could not be identified using 16O/18O and 2H/H. In addition, the SWAT model calculated that around 68% of the rainfall occurring in the catchment is lost through evapotranspiration reflecting the prevailing long-term drought conditions that were observed prior and during the study. Stream discharge from the forested subcatchment was an order of magnitude lower than discharge from the agricultural Six Mile Creek subcatchment. A change in land use from forestry to agriculture did not significantly change the catchment water balance, however, nutrient loads increased considerably. Conversely, a simulated change from agriculture to forestry resulted in a significant decrease of nitrogen loads.
The findings of the thesis and the approach used are shown to be of value to catchment water quality monitoring on a wider scale, in particular the implications of mixed land use on nutrient forms, distributions and concentrations. The study confirms that in the tropics and subtropics the water balance is affected by extended dry periods and seasonal rainfall with intensive storm events. In particular, the comprehensive data set of inorganic and organic N and P forms in the surface and groundwaters of this subtropical setting acquired during the one year sampling program may be used in similar catchment hydrological studies where these detailed information is missing. Also, the study concludes that riparian buffer zones along the catchment drainage system attenuate the transport of nitrogen from agricultural sources in the surface water. Concentrations of N decreased from upstream to downstream locations and were negligible at the outlet of the catchment.
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Dahl, Magnus. "Appropriate Modelling Complexity: An Application to Mass Balance Modelling of Lake Vänern, Sweden". Doctoral thesis, Uppsala University, Department of Earth Sciences, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4239.
Testo completoAbstract (sommario):
This work is about finding an appropriate modelling complexity for a mass-balance model for phosphorus in Lake Vänern, Sweden. A statistical analysis of 30 years of water quality data shows that epilimnion and hypolimnion have different water quality and should be treated separately in a model. Further vertical division is not motivated. Horizontally, the lake should be divided into the two main basins Värmlandssjön and Dalbosjön. Shallow near shore ares, bays and areas close to point sources have to be considered as specific sub-basins if they are to be modelled correctly.
These results leads to the use of a model based on ordinary differential equations. The model applied is named LEEDS (Lake Eutrophication Effect Dose Sensitivity) and considers phosphorus and suspended particles. Several modifications were made for the application of the model to Lake Vänern. The two major ones are a revision of the equations governing the outflow of phosphorus and suspended particle through the outflow river, and the inclusion of chemical oxygen demand (COD) into the model, in order to model emissions from pulp and paper mills. The model has also been modified to handle several sub-basins.
The LEEDS model has been compared to three other eutrophication models applied to Lake Vänern. Two were simple models developed as parts of catchment area models and the third was a lake model with higher resolution than the LEEDS model. The models showed a good fit to calibration and validation data, and were compared in two nutrient emission scenarios and a scenario with increased temperature, corresponding to the green house effect.
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Arendt, Anthony Alan. "Approaches to modelling the mass balance of High Arctic glaciers". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq22565.pdf.
Testo completo
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Ranasinghe, Milinda A. "Modelling the mass and energy balance in a compost biofilter". Thesis, University of Canterbury. Chemical and Process Engineering, 2003. http://hdl.handle.net/10092/7492.
Testo completoAbstract (sommario):
A biofilter model was developed using the mass and energy balances in the gas, liquid and solid phases, which related the biofilter performance to the water content in the packing material. A key simplification of the model was that the concentration gradients in the biofilm were neglected by treating the biofilm/water layer as well mixed and in instantaneous equilibrium with the gas phase. Thus, the biofilm geometry and density parameters were lumped into the overall degradation term. The solid phase was treated as a separate well-mixed layer but solid phase dynamics were accounted for by using the Linear Driving Force (LDF) mass transfer model. The mixed form of Richard's equation together with experimentally obtained unsaturated hydraulic conductivity and water retention curves for compost were used in the continuity equation for the liquid water phase. This approach produced a model where all parameters could be potentially independently determined.
The model was used to test suitable irrigation strategies for a biofilter system degrading toluene subject to different operational conditions. Under this approach both unidirectional and directionally switched biofilter configurations were tested for a 1 m long column. The unidirectional schemes incorporated both open and closed loop irrigation schemes, where the latter was based on commonly used on-line moisture measurement techniques. All schemes were evaluated based on the removal efficiency achieved and the leachate produced. Simulations under a constant irrigation rate of 5.46x 10⁻²g/m²s for a mass loading range of 13-60 g/m³h yielded removals ranging from 88%-26%. An order of magnitude drop in leachate under the high loading indicated severe drying in the system. For a high mass loading of 60 g/m³h, directional switching with a one-day frequency yielded a removal of 33% Vs 26% in an up flow scheme with similar leachate rates. Feedback control on water content provided an improved removal of 84% as compared to 73% under constant irrigation, when both schemes were subjected to load and inlet air step disturbances from 13 g/m³h to 62 g/m³h and from 298 K to 283 K respectively. A sensitivity analysis indicated that the model was most sensitive to the relationship between moisture content and degradation, which was also reflected by the high sensitivity of the model to the kinetic parameters in the degradation term.
A novel batch recycle reactor was thus developed to investigate the effect of water content changes on the degradation rate in low water content systems such as biofilters. The reactor tightly controlled the water content of the unsaturated packing material by using the principle of a suction cell. Experimental runs were performed with toluene as the contaminant using unamended compost at a constant temperature of 30°C. Matric potential in the compost was maintained at values between -6 and -36 cm H₂O and the gas phase was monitored by sampling/gas chromatography. A soil water retention curve relating matric potential to gravimetric water content was generated for the compost. Periodic dry weight analyses of reactor samples together with the water retention curve verified moisture content control. Degradation results demonstrated a biologically limited region followed by a non-linear region at lower concentrations. Elimination capacities were obtained along the wetting and drying curves and changes in the water content affected the removal rates in the linear region ranging from 155 g/m³h to 24 g/m³h over the matric potential range investigated. Repeatability studies indicated that moisture content was the most likely parameter that influenced the changes in performance. Batch scale experiments were also performed using microbially inhibited compost, which provided linear sorption isotherms for toluene on compost at concentrations between 0-1000 ppmv and temperature values of 25°C and 35°C.
The simulation model developed here provides a useful tool to implement and evaluate various operational schemes under different irrigation strategies. This is achieved by way of greater flexibility in incorporating the various schemes into the base model and the comparatively low simulation time to obtain the relevant results.
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Vernon, Christopher L. "Surface mass balance model intercomparison for the Greenland ice sheet". Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.633454.
Testo completoAbstract (sommario):
our simulations of the surface mass balance (SMB) of the Greenland ice sheet (GrIS) are compared over the period 1960-2008. Three use a regional climate model to downscale ECMWF reanalysis (ERA-40) and operational analysis data, while the fourth uses the same inputs but an empirical downscaling approach and melt model. These reconstructions have been used in a variety of applications but prior to this study little was known about their consistency with each other and the impact of the downscaling method on the result. The reconstructions are compared to assess the consistency in regional, seasonal and integrated 5MB components and evaluated against a suite of observational data. Three key areas of difference between the models have been identified. Firstly differences in how the ERA-40 reanalysis data are downscaled by the models. Secondly differences in how the 5MB components are calculated. And thirdly differences in the domain, the ice sheet mask used. Total 5MB estimates for the GrIS are in agreement within 34% of the four-model average when a common ice sheet mask is used. When models' native land/ice/sea masks are used this spread increases to 57%. The components of 5MB, with the exception of refreeze, show a similar level of agreement once a common mask is used. Previously noted differences in the models I estimates are partially explained by ice sheet mask differences. Agreement is higher (18% spread) in the accumulation area than the ablation area (38% spread) suggesting relatively high uncertainty in the estimation of ablation processes. Regionally there is less agreement, suggesting spatially compensating errors improve the integrated estimates. Modelled 5MB estimates are compared with in situ observations, gravimetric observations from GRACE and altimetry observations from ICESat. Through the use of a surface density and firn compaction model individual components of 5MB are, indirectly, able to be evaluated against altimetry observation.
Libri sul tema "Surface mass balance modelling"
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March, Rod. Mass balance, meteorological, ice motion, surface altitude, and runoff data at Gulkana Glacier, Alaska, 1992 balance year. Fairbanks, Alaska: Dept. of Interior, U.S. Geological Survey, 1996.
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March, Rod. Mass balance, meteorological, ice motion, surface altitude, and runoff data at Gulkana Glacier, Alaska, 1992 balance year. Fairbanks, Alaska: U.S. Geological Survey, 1996.
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3
March, Rod. Mass balance, meteorological, ice motion, surface altitude, and runoff data at Gulkana Glacier, Alaska, 1992 balance year. Fairbanks, Alaska: U.S. Geological Survey, 1996.
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4
March, Rod. Mass balance, meteorological, ice motion, surface altitude, and runoff data at Gulkana Glacier, Alaska, 1992 balance year. Fairbanks, Alaska: U.S. Dept. of the Interior, Geological Survey, 1996.
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Giovinetto, Mario B. Summary and analyses of surface mass balance compilations for Antarctica, 1960-1985. Columbus, Ohio: Byrd Polar Research Center, the Ohio State University, 1987.
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Giovinetto, Mario B. Summary and analysis of surface mass balance compilations for Antarctica, 1960-1985. Columbus: Ohio State University Research Foundation, 1987.
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March, Rod. Mass balance, meteorological, ice motion, surface altitude, and runoff data at Gulkana Glacier, Alaska, 1993 balance year. Fairbanks, Alaska: U.S. Geological Survey, 1997.
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March, Rod. Mass balance, meteorological, ice motion, surface altitude, and runoff data at Gulkana Glacier, Alaska, 1993 balance year. Fairbanks, Alaska: U.S. Dept. of the Interior, U.S. Geological Survey, 1997.
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March, Rod. Mass balance, meteorological, ice motion, surface altitude, and runoff data at Gulkana Glacier, Alaska, 1993 balance year. Fairbanks, Alaska: U.S. Geological Survey, 1997.
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March, Rod. Mass balance, meteorological, ice motion, surface altitude, and runoff data at Gulkana Glacier, Alaska, 1993 balance year. Fairbanks, Alaska: U.S. Dept. of the Interior, U.S. Geological Survey, 1997.
Cerca il testo completoCapitoli di libri sul tema "Surface mass balance modelling"
1
Oerlemans, J. "Modelling of Glacier Mass Balance". In Ice in the Climate System, 101–16. Berlin, Heidelberg: Springer Berlin Heidelberg, 1993. http://dx.doi.org/10.1007/978-3-642-85016-5_6.
Testo completo
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Maykut, Gary A. "The Surface Heat and Mass Balance". In The Geophysics of Sea Ice, 395–463. Boston, MA: Springer US, 1986. http://dx.doi.org/10.1007/978-1-4899-5352-0_6.
Testo completo
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Janoušek, Vojtěch, e Jean-François Moyen. "Mass Balance Modelling of Magmatic Processes in GCDkit". In Society of Earth Scientists Series, 225–38. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-06471-0_11.
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Bastin, Georges. "Issues in modelling and control of mass balance systems". In Stability and Stabilization of Nonlinear Systems, 53–74. London: Springer London, 1999. http://dx.doi.org/10.1007/1-84628-577-1_3.
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Gallée, Hubert, Cécile Agosta, Luc Gential, Vincent Favier e Gerhard Krinner. "A Downscaling Approach Toward High-Resolution Surface Mass Balance Over Antarctica". In The Earth's Cryosphere and Sea Level Change, 507–18. Dordrecht: Springer Netherlands, 2011. http://dx.doi.org/10.1007/978-94-007-2063-3_13.
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Mackay, Don, e Rajesh Seth. "The Role of Mass Balance Modelling in Impact Assessment and Pollution Prevention". In Tools and Methods for Pollution Prevention, 157–79. Dordrecht: Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-011-4445-2_12.
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Madsen, Heidi Ina, Jes Vollertsen e Thorkild Hvitved-Jacobsen. "Modelling the oxygen mass balance of wet detention ponds receiving highway runoff". In Alliance For Global Sustainability Bookseries, 487–97. Dordrecht: Springer Netherlands, 2007. http://dx.doi.org/10.1007/978-1-4020-6010-6_42.
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Mahesh, B., S. Dhanush, C. Rakshita, K. R. Raghavendra e M. Geetha Priya. "Antarctic Ice Sheet Surface Mass Balance Using UAV-Based Digital Elevation Model". In Communications in Computer and Information Science, 39–49. Cham: Springer Nature Switzerland, 2024. http://dx.doi.org/10.1007/978-3-031-60725-7_4.
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Pirch, N., E. W. Kreutz, B. Ollier e X. He. "The modelling of heat, mass and solute transport in surface processing with laser radiation". In Laser Processing: Surface Treatment and Film Deposition, 177–93. Dordrecht: Springer Netherlands, 1996. http://dx.doi.org/10.1007/978-94-009-0197-1_9.
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Bengtsson, Lennart, Symeon Koumoutsaris e Kevin Hodges. "Large-Scale Surface Mass Balance of Ice Sheets from a Comprehensive Atmospheric Model". In The Earth's Cryosphere and Sea Level Change, 459–74. Dordrecht: Springer Netherlands, 2011. http://dx.doi.org/10.1007/978-94-007-2063-3_10.
Testo completoAtti di convegni sul tema "Surface mass balance modelling"
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Garg, Purushottam Kumar, Sandipan Mukherjee, Mohit Prajapati e Ashutosh Tiwari. "Glacier Area, Mass Balance and Surface Ice Velocity Estimations in the Rulung Massif, Ladakh: Exploring High Altitude Glacier Changes". In IGARSS 2024 - 2024 IEEE International Geoscience and Remote Sensing Symposium, 156–59. IEEE, 2024. http://dx.doi.org/10.1109/igarss53475.2024.10642257.
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Pasternak, Viktoriya, Artem Ruban, Yurii Horbachenko e Sergii Vavreniuk. "Computer Modelling of the Process of Separation of Heterogeneous Elements (Spheres)". In International Scientific Applied Conference "Problems of Emergency Situations", 127–36. Switzerland: Trans Tech Publications Ltd, 2024. http://dx.doi.org/10.4028/p-5aamef.
Testo completoAbstract (sommario):
This scientific study considers the results of a computer experiment with heterogeneous elements (spheres) that proved to be of decisive importance during the separation process, namely their degree of activity, mobility and falling. It has been found that a detailed analysis of the Liapunov function indices allows to effectively understand and predict the dynamics of complex dynamical systems. The results obtained indicate significant changes in the physical and mechanical parameters of spherical balls under the influence of various factors and the environment. It was found that a certain accumulation of spheres occurs due to an increase in the time for simulation. It was also found that the key characteristics of the bulk mass of spherical elements significantly depend on the moulding process, surface condition and environmental conditions.
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Conceição, Eusébio, Maria Inês Conceição, Maria Manuela Lúcio, João Gomes e Hazim Awbi. "Human Design, Comfort and Discomfort Evaluation". In 8th International Conference on Human Interaction and Emerging Technologies. AHFE International, 2022. http://dx.doi.org/10.54941/ahfe1002712.
Testo completoAbstract (sommario):
In this work the human design, the thermal comfort and the local thermal discomfort are evaluated. In the design the human geometry is developed for a standard seating occupant. In the thermal comfort the PMV and the PPD indexes are calculated. In the local thermal discomfort, the Draught Risk is evaluated. The study, that considers the Human Thermal Modelling, calculates the evolution of the temperature in the body, namely in the skin and cold and warm thermo-receptors. The thermal comfort is dependent of the heat exchange between the body and the environment and the draught risk is dependent of the air temperature, air velocity and air turbulence intensity. The Human Thermal Modelling, that works in steady state and transient conditions, is based not only on the energy balance integral equations for the human body tissue, arterial and venous blood, but also on mass balance integral equations for the blood and transpired water in the skin surface. The clothing thermal system is based not only on the energy balance integral equations for the clothing, but also on mass balance integral equations for the transpired water in the clothing. In the thermal comfort, a mean air velocity is considered in steady state conditions, while in the Draught Risk two different air velocities Root Mean Square are considered in transient conditions.
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Borghi, Massimo, e Barbara Zardin. "Axial Balance of External Gear Pumps and Motors: Modelling and Discussing the Influence of Elastohydrodynamic Lubrication in the Axial Gap". In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-51632.
Testo completoAbstract (sommario):
This paper focuses on the analysis of hydraulically balanced external gear pumps, in particular on the lubricating gap between the bushes and the gears. This topic is of key importance for the optimization of the machine efficiency because it both influences the mechanical-viscous friction and the volumetric losses. In this paper the intent is to investigate the role of the elastic deformation of the bushes surfaces, to compare the analysis done with rigid and elastic surfaces and finally to correlate the results with the design of the bushes balancing surfaces. A numerical procedure for the determination of the pressure distribution inside the gap bounded by gears sides and the bushes internal surfaces is presented and applied. With respect to past works of the authors, the procedure has been integrated taking into account the elastic deformation of the internal surfaces of the bushes and the variation of the dynamic viscosity of fluid, two well recognized phenomena that can play a key role on the determination of the bushes behaviour and lubricating gap pressure distribution. It is shown that, when the design of the bushes rear surfaces determines a strong balancing thrust, the bushes themselves need to tilt strongly with respect to the gears to generate an opportune widening thrust to avoiding contact with the gears. Useful suggestions for the bushes balancing surface design may be drawn from the analysis of the balancing maps reported in the paper, which illustrate the widening thrust magnitude and position in both the pure hydrodynamic and elasto-hydrodynamic cases, for different tilted positions and operating conditions.
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Lecoq, Maxime, Nicholas Grech, Pavlos K. Zachos e Vassilios Pachidis. "Probabilistic and Numerical Modelling of a Lobed Mixer at Windmilling Conditions". In ASME Turbo Expo 2013: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gt2013-94366.
Testo completoAbstract (sommario):
Aero-gas turbine engines with a mixed exhaust configuration offer significant benefits to the cycle efficiency relative to separate exhaust systems, such as increase in gross thrust and a reduction in fan pressure ratio required. A number of military and civil engines have a single mixed exhaust system designed to mix out the bypass and core streams. To reduce mixing losses, the two streams are designed to have similar total pressures. In design point whole engine performance solvers, a mixed exhaust is modelled using simple assumptions; momentum balance and a percentage total pressure loss. However at far off-design conditions such as windmilling and altitude relights, the bypass and core streams have very dissimilar total pressures and momentum, with the flow preferring to pass through the bypass duct, increasing drastically the bypass ratio. Mixing of highly dissimilar coaxial streams leads to complex turbulent flow fields for which the simple assumptions and models used in current performance solvers cease to be valid. The effect on simulation results is significant since the nozzle pressure affects critical aspects such as the fan operating point, and therefore the windmilling shaft speeds and air mass flow rates. This paper presents a numerical study on the performance of a lobed mixer under windmilling conditions. An analysis of the flow field is carried out at various total mixer pressure ratios, identifying the onset and nature of recirculation, the flow field characteristics, and the total pressure loss along the mixer as a function of the operating conditions. The data generated from the numerical simulations is used together with a probabilistic approach to generate a response surface in terms of the mass averaged percentage total pressure loss across the mixer, as a function of the engine operating point. This study offers an improved understanding on the complex flows that arise from mixing of highly dissimilar coaxial flows within an aero-gas turbine mixer environment. The total pressure response surface generated using this approach can be used as look-up data for the engine performance solver to include the effects of such turbulent mixing losses.
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Tropea, Cam, e Ilia V. Roisman. "Spray Impact Onto a Rigid Wall: Modelling Strategy". In ASME 2002 Joint U.S.-European Fluids Engineering Division Conference. ASMEDC, 2002. http://dx.doi.org/10.1115/fedsm2002-31392.
Testo completoAbstract (sommario):
The common approach to the modelling of spray impact is to treat the phenomenon as a simple superposition of single drop impact events [1]. The main input for such model formulation is obtained either from experimental [2,3] or theoretical [4,5,6] studies of the impact of a single drop onto a dry wall, onto a uniform, undisturbed liquid film or into a deep pool [7]. However, in [8] it was shown that this conventional approach is not universal in the description of the spray impact and that in the case of relatively dense sprays, the interaction of crowns (Fig. 1) and the oscillations of the liquid-wall film must be taken into account. For example, these interactions result in the emerging of uprising jets during spray impingement of the diesel spray (see Fig. 2). In the study of spray impact we have chosen the following strategy of the modelling: 1. Description (experimental and theoretical) of single dropimpact. Determining of the parameters influencing the splash. 2. Description of the interaction of two drops on the wall surface. 3. Determining of the parameters of the single drop impacts influencing the dynamics of the film formed on the wall. Characterization of the film: the time averaged thickness, the time averaged velocity and its fluctuations. 4. Description of the influence of the oscillating motion of the film on the outcome from a single drop impact. Single drop impact onto a wetted wall—The motion of a kinematic discontinuity in the liquid film on the wall due to the drop impact, the formation of the uprising jet at this kinematic discontinuity and its elevation are analyzed. The theory [4] for the propagation of the kinematic discontinuity is generalized for the case of arbitrary velocity vectors in the inner and outer liquid films on the wall. Next, the mass, momentum balance and Bernoulli equations at the base of the crown are considered to obtain the velocity and the thickness of the jet on the wall. An analytical solution for the crown shape is obtained in the asymptotic case of such high impact velocities that the surface tension and the viscosity effects can be neglected in comparison to inertial effects. The edge of the crown is described by the motion of a rim, formed due to the surface tension. The theoretical predictions of the height of the crown are compared with experiments. The agreement is rather good in spite of the fact that no adjustable parameters are used (see Fig. 3). Three different cases are considered: normal axisymmetric impact of a single drop, oblique impact of a single drop, and impact and interaction of two drops. Next, two new parameters of single drop impact influencing the dynamics of the film formed due to the polydisperse spray impact are identified. The first one is associated with the relative presence of the crown on the film surface and allowing one to estimate the probability of crown interactions. The second parameter is associated with the axial momentum in the plane of the wall. Time-averaged film motion—The theory of the creation of the film by spray can be subdivided into three main parts: 1. The characterization of the spray, particularly definition of the flux vectors of scalar properties (number flux vector, volume flux vector, etc.) and the momentum flux tensor. 2. Boundary conditions at the time-averaged spray/film boundary. 3. Dynamics of the film motion on the wall. The mass and momentum equations of the film are formulated accounting for the volume flux of the spray, the dynamic pressure, and the time-averaged stress vector at the film “free” surface caused by the inertia of the spray. The inertial terms of the liquid in the film contains of the inertia of the time-averaged motion and the inertia of film oscillations. These oscillations are modelled as an ensemble of the radial flows in the film associated with the single drop impacts. The probability of the crown interactions is also taken into account. Jetting at the film surface due to impingement of a dense spray—Here we consider impact of such dense sprays that the probability of single crown to propagate without interaction with another crown is very small. The non-uniformities in the dynamic pressure in such sprays yields the significant fluctuations in the film velocity leading to the shocks and jetting (as in the case of the diesel spray impact shown in Fig. 2). We describe the statistically averaged distribution of drop impacts around a given drop assuming that all the impacting drops are distributed randomly in space and in time. The statistically averaged dynamic pressure around given drop is not uniform either in the time or in the radial direction. The self-similar solution for the statistically averaged radial velocity in the film and its thickness (Fig. 4) is obtained. The characteristic time of the instant of shock is estimated. The theoretical predictions of the jets diameter agree with the experimental data in the order of the magnitude.
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Suckling, Paul, Nicola Calder, Paul Humphreys, Fraser King e Helen Leung. "The Development and Use of T2GGM: A Gas Modelling Code for the Postclosure Safety Assessment of OPG’s Proposed L&ILW Deep Geologic Repository, Canada". In ASME 2009 12th International Conference on Environmental Remediation and Radioactive Waste Management. ASMEDC, 2009. http://dx.doi.org/10.1115/icem2009-16291.
Testo completoAbstract (sommario):
As part of the postclosure safety assessment of Ontario Power Generation’s (OPG’s) proposed Deep Geologic Repository (DGR) for Low and Intermediate Level Waste (L&ILW) at the Bruce site, Ontario, a Gas Generation Model (GGM) has been developed and used to model the detailed generation of gas within the DGR due to corrosion and microbial degradation of the organics and metals present. The GGM is based on a kinetic description of the various microbial and corrosion processes that lead to the generation and consumption of various gases. It takes into account the mass-balance equations for each of the species included in the model, including three forms of organic waste (cellulose, ionexchange resins, and plastics and rubbers), four metallic waste forms and container materials (carbon and galvanised steel, passivated carbon steel, stainless steel and nickel-based alloys, and zirconium alloys), six gases (CO2, N2, O2, H2, H2S, and CH4), five terminal electron acceptors (O2, NO3−, Fe(III), SO42−, and CO2), five forms of biomass (aerobes, denitrifiers, iron reducers, sulphate reducers, and methanogens), four types of corrosion product (FeOOH, FeCO3, Fe3O4, and FeS), and water. The code includes the possibility of the limitation of both microbial and corrosion reactions by the availability of water. The GGM has been coupled with TOUGH2 to produce T2GGM; a code that models the generation of gas in the repository and its subsequent transport through the geosphere. T2GGM estimates the peak repository pressure, long time repository saturation and the total flux of gases from the geosphere. The present paper describes the development of T2GGM and the numerical modelling work undertaken to calculate the generation and build-up of gas in the repository, the two-phase exchange of gas and groundwater between the repository and the surrounding rock, and between the rock and the surface environment. The results have been used to inform the safety assessment modelling.
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Pohjoranta, A., e R. Tenno. "Modelling of Surfactant Mass Balance for Microvia Fill Monitoring". In High Density Design Packaging and Microsystem Integration, 2007 International Symposium on. IEEE, 2007. http://dx.doi.org/10.1109/hdp.2007.4283592.
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Cheung, Sherman C. P., Xinyue Duan, Guan H. Yeoh, Jiyuan Tu, Eckhard Krepper, Dirk Lucas, Liejin Guo et al. "Modelling of Polydispersed Flows using Two Population Balance Approaches". In THE 6TH INTERNATIONAL SYMPOSIUM ON MULTIPHASE FLOW, HEAT MASS TRANSFER AND ENERGY CONVERSION. AIP, 2010. http://dx.doi.org/10.1063/1.3366467.
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Shankar, P., M. Raghunathan, N. Mohd Azam, A. N. Abu Bakar, N. Che Mahmood, M. Mohd Shaharudin, A. Abu Bakar et al. "Enhancing Value from a Mature Offshore Field: Sweet Spot Identification Leveraging Subsurface Insights and Analytical Reservoir Engineering for Optimal Infill Campaigns". In SPE Symposium and Exhibition - Production Enhancement and Cost Optimisation. SPE, 2024. http://dx.doi.org/10.2118/220627-ms.
Testo completoAbstract (sommario):
Abstract S-field situated offshore the Sabah coast in East Malaysia has been producing from multi-stacked, compartmentalized reservoirs for 45 years recovering ∼45% of the STOIIP and ha s undergone 10 development campaigns. Uncertainty on identifying sweet spots through dynamic modelling has been challenging owing to limitations on data acquisition/quality/reliability and inherent issues with the modelling approach, typical for a matured field. Results from the first well of recent drilling campaign offered striking surprises, which triggered application of classical reservoir engineering practices – resulted in a successful campaign. Higher EUR per well were achieved from rest of the campaign wherein quick decision making could be achieved through focussed and integrated multi-disciplinary approach. Building on this experience, the targets for an upcoming drilling campaign were achieved through analytical reservoir engineering, complemented with robust subsurface risk assessment -seismic, geology, petrophysical and reservoir engineering considerations. Reservoir targets were identified based on meticulous analysis of well/reservoir performance, open-hole logs, contact movement and seismic bright-spots. Drainage radii per zone around existing and past drainage points were established based on the EUR. The targets were screened visually on maps lest they should interfere with the drained areas. The targets were categorized as untapped reservoirs, attic oil, sweep and low-recovery areas, which helped in summarizing risks. Targets were stringed together in an optimal way by considering the possibility of commingling reservoirs within a single infill well, thereby reducing risks, minimizing costs, and maximizing recovery. Well trajectories were planned to target the identified sweet spots through fewer platforms utilizing empty slots or abandoned wells slots. A bespoke approach was adapted to check and mitigate crossflow between zones throughout the well-life cycle through network modelling involving the material balance and vertical flow performance models. The targeted zone-level STOIIP were derived based on GRV around them, clipped for contacts and faults, which were used as inputs for material balance models. The inflow properties for each zone were benchmarked productivity of existing wells stock. The forecast for each proposed well were calibrated with liquid production, water cut, and gas-oil ratio trends observed in nearby existing wells. With growing portfolio of mature fields in the industry, the application of analytical techniques is growing leaps and bounds in identifying sweet spots. Innovative approaches/workflows like the one illustrated in this paper are often found useful. The key enablers for identifying the infill locations and optimizing them are integration of data and application of basic knowledge of sub-surface domains. This paper is a good example to illustrate the importance of such workflow and enablers to extend the life of mature field and add value to the business.
Rapporti di organizzazioni sul tema "Surface mass balance modelling"
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Burgess, D. O. Validation of the RACMO2.3 surface mass-balance model over northwest Devon Ice Cap, Nunavut. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 2018. http://dx.doi.org/10.4095/308355.
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Kurtz, Deb, e Deb Kurtz. Northern Harding Icefield glacier mass balance summary: 2010?2017. National Park Service, 2025. https://doi.org/10.36967/2306622.
Testo completoAbstract (sommario):
Glaciers cover nearly half of Kenai Fjords National Park, serving an important role in ecosystem dynamics and attracting hundreds of thousands of visitors to the park each year. Glacial melt is important to park managers as it impacts visitor experience, infrastructure (e.g., trails and roads), and downstream habitats. Glacier mass balance is the annual gain and loss of ice calculated as a sum of seasonal measurements of accumulation and ablation (the loss of ice through melt, sublimation, and calving). Long-term glacier mass balance studies provide an established method for monitoring the status of glaciers and can be used to estimate rates of change and to predict thresholds and trigger points that could result in major changes to glacier extent and downstream systems. This report summarizes field efforts and results of eight years of stake-based mass balance measurements on the northern Harding Icefield, for water years 2010?2017. From 2010?2017, seasonal measurements were conducted at six sites on the northern Harding Icefield to quantify seasonal and annual point mass balances along an elevation gradient from 532 m to 1290 m. Cumulative winter mass balances range from 0.47 to 1.81 meters water equivalent (m w.e.) at the lowest site (532 m a.s.l), and 2.11 m w.e. to 3.43 m w.e. at the highest site with continuous annual data (1230 m a.s.l). Summer mass balances range from ?5.85 m w.e. to ?8.35 m w.e. at the lowest site (532 m a.s.l.) and ?0.54 to ?2.24 at the site located at 1230 m a.s.l.. Although all sites display interannual variability in the seasonal and annual mass balance, the general trend is of decreasing mass balance. The two sites at the lowest elevations are in the ablation zone and display persistent negative mass balances. The two sites at the middle elevations have been oscillating around a zero or neutral balance and are near the Equilibrium Line Altitude (ELA). The two sites at the highest elevations have positive balances (mass gain) but have shown a decrease over the period of measurements. This has resulted in significant surface melt and elevation loss at lower elevations of Exit Glacier over the period of record.
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Russell, H. A. J., e S. K. Frey. Canada One Water: integrated groundwater-surface-water-climate modelling for climate change adaptation. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/329092.
Testo completoAbstract (sommario):
Canada 1 Water is a 3-year governmental multi-department-private-sector-academic collaboration to model the groundwater-surface-water of Canada coupled with historic climate and climate scenario input. To address this challenge continental Canada has been allocated to one of 6 large watershed basins of approximately two million km2. The model domains are based on natural watershed boundaries and include approximately 1 million km2 of the United States. In year one (2020-2021) data assembly and validation of some 20 datasets (layers) is the focus of work along with conceptual model development. To support analysis of the entire water balance the modelling framework consists of three distinct components and modelling software. Land Surface modelling with the Community Land Model will support information needed for both the regional climate modelling using the Weather Research & Forecasting model (WRF), and input to HydroGeoSphere for groundwater-surface-water modelling. The inclusion of the transboundary watersheds will provide a first time assessment of water resources in this critical international domain. Modelling is also being integrated with Remote Sensing datasets, notably the Gravity Recovery and Climate Experiment (GRACE). GRACE supports regional scale watershed analysis of total water flux. GRACE along with terrestrial time-series data will serve provide validation datasets for model results to ensure that the final project outputs are representative and reliable. The project has an active engagement and collaborative effort underway to try and maximize the long-term benefit of the framework. Much of the supporting model datasets will be published under open access licence to support broad usage and integration.
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Zeller, Lucas, Daniel McGrath, Louis Sass, Shad O’Neel, Christopher McNeil e Emily Baker. Beyond glacier-wide mass balances : parsing seasonal elevation change into spatially resolved patterns of accumulation and ablation at Wolverine Glacier, Alaska. Engineer Research and Development Center (U.S.), maggio 2024. http://dx.doi.org/10.21079/11681/48497.
Testo completoAbstract (sommario):
We present spatially distributed seasonal and annual surface mass balances of Wolverine Glacier, Alaska, from 2016 to 2020. Our approach accounts for the effects of ice emergence and firn compaction on surface elevation changes to resolve the spatial patterns in mass balance at 10 m scale. We present and compare three methods for estimating emergence velocities. Firn compaction was constrained by optimizing a firn model to fit three firn cores. Distributed mass balances showed good agreement with mass-balance stakes (RMSE = 0.67 m w.e., r = 0.99, n = 41) and ground-penetrating radar surveys (RMSE = 0.36 m w.e., r = 0.85, n = 9024). Fundamental differences in the distributions of seasonal balances highlight the importance of disparate physical processes, with anomalously high ablation rates observed in icefalls. Winter balances were found to be positively skewed when controlling for elevation, while summer and annual balances were negatively skewed. We show that only a small percent of the glacier surface represents ideal locations for mass-balance stake placement. Importantly, no suitable areas are found near the terminus or in elevation bands dominated by icefalls. These findings offer explanations for the often needed geodetic calibrations of glaciological time series.
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Fassnacht, Steven, Kazuyoshi Suzuki, Jessica Sanow, Graham Sexstone, Anna Pfohl, Molly Tedesche, Bradley Simms e Eric Thomas. Snow surface roughness across spatio-temporal scales. Engineer Research and Development Center (U.S.), settembre 2024. http://dx.doi.org/10.21079/11681/49199.
Testo completoAbstract (sommario):
The snow surface is at the interface between the atmosphere and Earth. The surface of the snowpack changes due to its interaction with precipitation, wind, humidity, short- and long-wave radiation, underlying terrain characteristics, and land cover. These connections create a dynamic snow surface that impacts the energy and mass balance of the snowpack, blowing snow potential, and other snowpack processes. Despite this, the snow surface is generally considered a constant parameter in many Earth system models. Data from the National Aeronautics and Space Administration (NASA) Cold Land Processes Experiment (CLPX) collected in 2002 and 2003 across northern Colorado were used to investigate the spatial and temporal variability of snow surface roughness. The random roughness (RR) and fractal dimension (D) metrics used in this investigation are well correlated. However, roughness is not correlated across scales, computed here from snow roughness boards at a millimeter resolution and airborne lidar at a meter resolution. Process scale differences were found based on land cover at each of the two measurement scales, as appraised through measurements in the forest and alpine.
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Schlossnagle, Trevor H., Janae Wallace, e Nathan Payne. Analysis of Septic-Tank Density for Four Communities in Iron County, Utah - Newcastle, Kanarraville, Summit, and Paragonah. Utah Geological Survey, dicembre 2022. http://dx.doi.org/10.34191/ri-284.
Testo completoAbstract (sommario):
Iron County is a semi-rural area in southwestern Utah that is experiencing an increase in residential development. Although much of the development is on community sewer systems, many subdivisions use septic tank soil-absorption systems for wastewater disposal. Many of these septic-tank systems overlie the basin-fill deposits that compose the principal aquifer for the area. The purpose of our study is to provide tools for waterresource management and land-use planning. In this study we (1) characterize the water quality of four areas in Iron County (Newcastle, Kanarraville, Summit, and Paragonah) with emphasis on nutrients, and (2) provide a mass-balance analysis based on numbers of septic-tank systems, groundwater flow available for mixing, and baseline nitrate concentrations, and thereby recommend appropriate septic-system density requirements to limit water-quality degradation. We collected 57 groundwater samples and three surface water samples across the four study areas to establish baseline nitrate concentrations. The baseline nitrate concentrations for Newcastle, Kanarraville, Summit, and Paragonah are 1.51 mg/L, 1.42 mg/L, 2.2 mg/L, and 1.76 mg/L, respectively. We employed a mass-balance approach to determine septic-tank densities using existing septic systems and baseline nitrate concentrations for each region. Nitrogen in the form of nitrate is one of the principal indicators of pollution from septic tank soil-absorption systems. To provide recommended septic-system densities, we used a mass-balance approach in which the nitrogen mass from projected additional septic tanks is added to the current nitrogen mass and then diluted with groundwater flow available for mixing plus the water added by the septic-tank systems themselves. We used an allowable degradation of 1 mg/L with respect to nitrate. Groundwater flow volume available for mixing was calculated from existing hydrogeologic data. We used data from aquifer tests compiled from drinking water source protection documents to derive hydraulic conductivity from reported transmissivities. Potentiometric surface maps from existing publications and datasets were used to determine groundwater flow directions and hydraulic gradients. Our results using the mass balance approach indicate that the most appropriate recommended maximum septic-tank densities in Newcastle, Kanarraville, Summit, and Paragonah are 23 acres per system, 7 acres per system, 5 acres per system, and 11 acres per system, respectively. These recommendations are based on hydrogeologic parameters used to estimate groundwater flow volume. Public valley-wide sewer systems may be a better alternative to septic-tank systems where feasible.
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Stalker, Linda, Karsten Michael, Charles Jenkins, Kate Holland, Luk Peeters, Matt Myers e Andrew Ross. Reviewing the implications of unlikely but potential CO2 migration to the surface or shallow subsurface. IEAGHG, gennaio 2025. https://doi.org/10.62849/2025-01.
Testo completoAbstract (sommario):
CO2 leakage from geological storage is considered unlikely from properly selected sites and the potential impacts small when compared to other anthropogenic and natural stressors. However, it is important to predict and understand potential environmental impacts and risks to human health from a range of leak scenarios in order to undertake appropriate monitoring and mitigation necessary to meet both regulatory and societal expectations. Migration of CO2 to the surface, subsurface or into potable water reservoirs poses a risk, and although is predicted to be rare and limited in quantity, cannot be excluded completely, especially via abandoned wells, along fault surfaces or via gas chimneys. Very strict interpretation of regulatory requirements may impose very high costs or limit the number and size of storage site unnecessarily, thus potentially reducing the regional and global storage resources severely. Given the important role that carbon capture and storage (CCS) plays, as a part of negative emission technologies (NETs) and emission reduction technologies, in most climate scenarios (IPCC, IEA and others), a balance between the merits of CCS on a global scale and the potential risks at a local scale, needs to be evaluated. A growing body of knowledge, gleaned over the past two decades into the environmental impact of leaked CO2 have included studying the impact of CO2 release in: natural seings, potable aquifers, via laboratory and controlled release experiments and modelling. It was desirable, therefore, that these learnings were summarised and evaluated in a clear and accessible document that would be of value to policymakers, project developers and regulators.
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Loso, Michael, e Michael Loso. Glacier monitoring in the Central Alaska Network: Protocol narrative, version 1.0. National Park Service, 2025. https://doi.org/10.36967/2308209.
Testo completoAbstract (sommario):
Two of the three national parks that comprise the National Park Service Inventory & Monitoring Program?s Central Alaska Network (CAKN) are covered by large quantities of glacier ice. Wrangell-St. Elias National Park and Preserve has 3,121 glaciers and Denali National Park and Preserve has 881. These glaciers cover significant portions of the parks and exert substantial influence over the surrounding landscapes with impacts on weather, vegetation, animal migration, river flow, aquatic life, and even downstream marine ecosystems. They also provide a significant attraction?and hazard?for visitors. These glaciers are changing rapidly, primarily due to the influence of warming air temperatures. The impacts of glaciers on park resources and park visitors are not only important, but quickly evolving, with important consequences for park management. For all these reasons, the Central Alaska Network has identified glaciers as one of the vital signs that should undergo long-term monitoring. This document describes the protocol for conducting that monitoring program. Glacier monitoring in the CAKN parks began in 1991 with measurements of mass balance (snow accumulation and melt) and surface elevation at one site on Denali?s Kahiltna Glacier. The monitoring has evolved since that time to include mass balance measurements on a second large glacier (Kennicott Glacier) in Wrangell-St. Elias. Those two glaciers are highly visited, compared to most other glaciers in the parks, and are relatively accessible for monitoring purposes. The objectives of these measurements are to document seasonal and interannual changes in the primary climatic forces that control glacier change: snow accumulation and melt. Combined with periodic remeasurements of the glacier boundaries and surface elevations, the protocol records mass balances of these two glaciers with both glaciological and geodetic methods, allowing analysis of total mass balance with accompanying understanding of the climatic forces behind it. The glacier monitoring protocol also calls for the use of increasingly available remote sensing techniques to document changes in glacier areas, surface elevations, and surface velocities for a broad collection of park glaciers. Outside the scope of the CAKN protocol, boundaries of all park glaciers have been digitized twice over the last decade, and this protocol calls for continuation of that decadal inventory using whatever remote sensing data and techniques are most applicable at each decadal time step. A subset of the largest park glaciers is also slated for measurement of surface elevations every 4-6 years, continuing the measurements made by Operation IceBridge since the mid-1990s.
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Schlossnagle, Trevor H., e Torri Duncan. Analysis of Septic-Tank Density for Rockville, Washington County, Utah. Utah Geological Survey, settembre 2024. http://dx.doi.org/10.34191/ri-288.
Testo completoAbstract (sommario):
Rockville is a small rural town in southwestern Utah that is experiencing an increase in residential development. New developments in rural areas often use septic tank soilabsorption systems for wastewater disposal, although there is potential to utilize an existing community sewer system. Because potential future septic-tank systems may overlie the principal drinking water aquifer for Rockville, city off icials asked the Utah Geological Survey to conduct a septictank density analysis. The purpose of our study is to provide tools for water-resource management and land-use planning. In this study we (1) characterize the groundwater quality of Rockville with an emphasis on nitrate, and (2) provide a mass-balance analysis for three subdomains (Virgin River corridor, South Mesa, South Mesa subdivision) based on numbers of septic-tank systems, groundwater flow available for mixing, and baseline nitrate concentrations, and thereby determine appropriate septic-system density requirements to limit water-quality degradation. There are two aquifers commonly utilized in Rockville: The Shinarump Conglomerate (primary aquifer) and the Shnabkaib Member of the Moenkopi Formation and overlying alluvial deposits along the Virgin River (secondary aquifer). Using 11 groundwater samples taken from water wells and a spring, we established that baseline nitrate concentrations for these two Rockville aquifers are low, at 0.1 mg/L for the primary aquifer and 0.26 mg/L for the secondary aquifer. To determine the ideal septic-tank density, we employed a mass-balance approach using existing septic systems and baseline nitrate concentrations. Nitrogen in the form of nitrate is one of the principal indicators of pollution from septic tank soil-absorption systems. For the mass-balance approach, the nitrogen mass from projected additional septic tanks is added to the current nitrogen mass and then diluted with groundwater flow available for mixing plus the water added by the septic-tank systems themselves. We used an allowable degradation of 1 mg/L with respect to nitrate. Groundwater flow volume available for mixing was calculated from existing hydrogeologic data. We used data from aquifer tests and specific capacity data from water well logs to derive hydraulic conductivity for Rockville’s aquifers. Existing publications and potentiometric surface datasets were used to determine groundwater flow directions and hydraulic gradients. Our results using the mass balance approach indicate that the most conservative septic-tank densities for the Virgin River corridor, South Mesa, and South Mesa subdivision subdomains are 11 acres per system, 13 acres per system, and 8 acres per system, respectively. Due to the low baseline nitrate concentrations, higher septic-tank densities may still be conservative enough to protect water quality. These determinations are based on hydrogeologic parameters used to estimate groundwater flow volume. Connecting to existing community sewer systems may be a safer alternative to septic-tank systems where feasible.
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Dasberg, Shmuel, Jan W. Hopmans, Larry J. Schwankl e Dani Or. Drip Irrigation Management by TDR Monitoring of Soil Water and Solute Distribution. United States Department of Agriculture, agosto 1993. http://dx.doi.org/10.32747/1993.7568095.bard.
Testo completoAbstract (sommario):
Drip irrigation has the potential of high water use efficiency, but actual water measurement is difficult because of the limited wetted volume. Two long-term experiments in orchards in Israel and in California and several field crop studies supported by this project have demonstrated the feasibility of precise monitoring of soil water distribution for drip irrigation in spite of the limited soil wetting. Time Domain Reflectometry (TDR) enables in situ measurement of soil water content of well defined small volumes. Several approaches were tried in monitoring the soil water balance in the field during drip irrigation. These also facilitated the estimation of water uptake: 1. The use of multilevel moisture probe TDR system. This approach proved to be of limited value because of the extremely small diameter of measurement. 2. The placement of 20 cm long TDR probes at predetermined distances from the drippers in citrus orchards. 3. Heavy instrumentation with neutron scattering access tubes and tensiometers of a single drip irrigated almond tree. 4. High resolution spatial and temporal measurements (0.1m x 0.1m grid) of water content by TDR in corn irrigated by surface and subsurface drip. The latter approach was accompanied by parametric modelling of water uptake intensity patterns by corn roots and superimposed with analytical solutions for water flow from point and line sources. All this lead to general and physically based suggestions for the placement of soil water sensors for scheduling drip irrigation.