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1
MacLeod, R. I. "Dynamics of the Antarctic mesosphere /." Title page, contents and summary only, 1986. http://web4.library.adelaide.edu.au/theses/09PH/09phm1658.pdf.
Texte intégral
2
Lange, Martin, and Christoph Jacobi. "Einfluß des winterlichen stratosphärischen Polarwirbels auf die zonale Symmetrie des Windfeldes in der oberen Mesosphäre und unteren Thermosphäre simuliert mit dem COMMA-Modell." Universitätsbibliothek Leipzig, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-216894.
Texte intégralRésumé :
Langzeitmessungen des Windfeldes in der Mesopausenregion (~ 92km) an verschiedenen Stationen in den mittleren Breiten der Nordhemisphäre zeigen systematische zonale Variationen beim (zeitlich) gemittelten Zonal- und Meridionalwind und bei den Amplituden und Phasen der halbtägigen Gezeiten. Als eines der herausragenden Muster, die zonale Variationen in der unteren mittleren Atmosphäre anregen, wird der Einfluß der Geopotentialstörungen zur zonalen Wellenzahl 1 und 2, die mit dem winterlichen stratosphärischen Polarwirbel verbunden sind, auf das Windfeld in der oberen Mesosphäre / unteren Thermosphäre numerisch mit dem COMMA-Modell der mittleren Atmosphäre untersucht. Die Modellergebnisse zeigen eine gute Übereinstimmung der zonalen Variationen des mittleren Zonalwindes, die im Breitenbereich 52ÆN bis 56ÆN beobachtet werden und in der Größenordnung von 10 - 20 m/s liegen. Auch die halbtägigen Gezeitenamplituden und -phasen zeigen qualitative und quantitative Übereinstimmungen zwischen Beobachtungen und Modellergebnissen<br>Long-term time series of wind field observations in the upper mesosphere / lower thermosphere region at different locations in the midlatitude region indicate longitudinal variability in the (time-) mean zonal and meridional wind and in the amplitudes and phases of the semidiurnal tide, too. Being one of the prominent patterns forcing zonal inhomogenities in the lower middle atmosphere, the influence of the zonal wavenumber 1 and wavenumber 2 disturbances connected with the winter Northern Hemisphere stratospheric polar vortex on the mesosphere- / lower thermosphere wind field is numerically investigated with the COMMA model. The model results show that the zonal variations through the stationary waves coincide with typical observed mean zonal wind differences between different stations along the midlatitude belt between 52ÆN and 56ÆN with values about 10- 20 m/s. Also, the amplitude and phase variations of the semidiurnal tide show qualitative and quantitative agreements between model results and observations
3
Jacobi, Christoph, and Peter Braesicke. "Correlation between stratosphere and upper mesosphere." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-214575.
Texte intégralRésumé :
Collm mesopause winds are analysed with respect to their correlation with 30 hPa northern hemispheric stratospheric winds and pressure level heights. Correlation maps, based on the period of December 1978 through November 1997, are presented for each month of the year, showing possible connections between the lower and upper middle atmosphere, partly owing to the 10-12-year oscillation (TTO). Although in winter due to the propagation of planetary waves into the mesosphere direct coupling between the different layers of the atmosphere especially during stratospheric warmings is possible, the strongest correlation between stratosphere and mesopause region is found in summer, which is for the most part connected with the solar cycle dependence of the middle atmosphere<br>Die Mesopausenwinddaten vom Collm werden in Bezug auf ihre Verbindung mit stratosphärischen Winden und Druckhöhen in 30 hPa untersucht. Abbildungen der Korrelationskoeffizienten, basierend auf dem Zeitraum von Dezember 1978 bis November 1997 zeigen mögliche Verbindungen zwischen Stratosphäre und Mesopausenregion, zum Teil über die 10-12-jährige Schwingung (TTO) der Stratosphäre. Obwohl im Winter wegen der Ausbreitung planetarer Wellen in die Mesosphäre speziell während rascher Stratosphärenerwärmungen eine direkte Verbindung zwischen den Schichten der Atmosphäre auftritt, werden die stärksten Korrelationen im Sommer gefunden, größtenteils durch den Einfluß der TTO
4
Jacobi, Christoph, Nadja Samtleben, and Gunter Stober. "Meteor radar observations of mesopause region long-period temperature oscillations." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-212263.
Texte intégralRésumé :
Meteor radar observations of mesosphere/lower thermosphere (MLT) daily temperatures have been performed at Collm, Germany since August 2004. The data have been analyzed with respect to long-period oscillations at time scales of 2–30 days. The results reveal that oscillations with periods of up to 6 days are more frequently observed during summer, while those with longer periods have larger amplitudes during winter. The oscillations may be considered as the signature of planetary waves. The results are compared with analyses from radar wind measurements. Moreover, the temperature oscillations show considerable year-to-year variability. In particular, amplitudes of the quasi 5-day oscillation have increased during the last decade, and the quasi 10-day oscillations are larger if the equatorial stratospheric winds are eastward.
5
Moss, Andrew. "Wave dynamics of the stratosphere and mesosphere." Thesis, University of Bath, 2017. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.707571.
Texte intégralRésumé :
Gravity waves play a fundamental role in driving the large-scale circulation of the atmosphere. They are influenced both by the variation in their sources and the filtering effects of the winds they encounter as they ascend through the atmosphere. In this thesis we present new evidence that gravity waves play a key role in coupling the troposphere, stratosphere and mesosphere. In particular, we examine the connection of gravity waves to two important large-scale oscillations that occur in the atmosphere, namely the Madden-Julian Oscillation (MJO) in the troposphere and the Mesospheric Semi-Annual Oscillation (MSAO). We present the first ever demonstration that the MJO acts to modulate the global field of gravity waves ascending into the tropical stratosphere. We discover a significant correlation with the MJO zonal-wind anomalies and so suggest that the MJO modulates the stratospheric gravity-wave field through a critical-level wave-filtering mechanism. Strong evidence for this mechanism is provided by consideration of the winds encountered by ascending waves. The Ascension Island meteor radar is used for the first time to measure momentum fluxes over the Island. These measurements are then used to investigate the role of gravity-wave in driving a dramatic and anomalous wind event that was observed to occur during the first westward phase of the MSAO in 2002. Gravity waves are shown to play an important role in driving this event, but the observations presented here also suggest that the current theory of the mechanism describing these anomalous mesospheric wind events is not valid. Both of these studies highlight the critical importance of gravity waves to the dynamics of the atmosphere and highlight the need for further work to truly understand these waves, their processes and their variability.
6
Beldon, Charlotte. "VHF radar studies of mesosphere and thermosphere." Thesis, University of Bath, 2008. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.512294.
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7
Sandford, David J. "Dynamics of the stratosphere, mesosphere and thermosphere." Thesis, University of Bath, 2008. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.512300.
Texte intégralRésumé :
This thesis presents observations of the dynamical features of the stratosphere, mesosphere and lower thermosphere. These are made from various observational techniques and model comparisons. A focus of the work is the two-day wave at high latitudes in the MLT region. This has revealed significant wave amplitudes in both summer and winter. However, these waves are shown to have very different origins. Using satellite data, the summertime wave is found to be the classic quasi-two-day wave which maximises at mid-latitudes in the MLT region. The wintertime wave is found to be a mesospheric manifestation of an eastward-propagating wave originating in the stratosphere and likely generated by barotropic and baroclinic instabilities in the polar night jet. The horizontal winds from Meteor and MF radars have been used to measure and produce climatologies of the Lunar M2 tide at Esrange in the Arctic (68°N), Rothera and Davis in the Antarctic (68°S), Castle Eaton at mid-latitude (52°N) and Ascension Island at Equatorial latitudes (8°S). These observations present the longest period of lunar semi-diurnal tidal observations in the MLT region to date, with a 16-year dataset from the UK meteor radar. Comparisons with the Vial and Forbes (1994) lunar tidal model are also made which reveal generally good agreement. Non-migrating lunar tides have been investigated. This uses lunar tidal results from equatorial stations, including the Ascension Island (8°S) meteor radar. Also lunar tidal results from the Rothera meteor wind radar (68°S, 68°W) and the Davis MF radar (68°S, 78°E) are considered. Both of these stations are on the edge of the Antarctic continent. It is demonstrated that there are often consistent tidal phase offsets between similar latitude stations. This suggests that non-migrating modes are likely to be present in the lunar semi-diurnal tidal structure and have significant amplitudes.
8
Holt, Gavin. "Planetary waves in the stratosphere and mesosphere." Thesis, University of Oxford, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318787.
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9
Greet, P. A. "Observations on the sodium airglow /." Title page, contents and abstract only, 1988. http://web4.library.adelaide.edu.au/theses/09PH/09phg8166.pdf.
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10
Phillips, A. "Dynamics of the Antarctic mesosphere and lower thermosphere /." Title page, contents and abstract only, 1989. http://web4.library.adelaide.edu.au/theses/09PH/09php5583.pdf.
Texte intégralRésumé :
Thesis (Ph. D.)--University of Adelaide, Mawson Institute for Antarctic Research, 1990.<br>Copies of author's previously published articles inserted. Includes bibliographical references (leaves 219-226).
11
Murphy, D. J. "Measurements of energy and momentum in the mesosphere /." Title page, table of contents and abstract only, 1990. http://web4.library.adelaide.edu.au/theses/09PH/09phm9772.pdf.
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12
Tingle, Susannah. "The dynamics of the Venusian mesosphere and thermosphere." Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/9060.
Texte intégralRésumé :
We present the first circulation model of Venus' atmosphere to couple the super-rotating cloud tops and upper thermosphere. To drive these simulations, we formulate the first continuous semi-empirical model of atmospheric structure between 60-250 km. Our model hydrostatically links the VIRA and VTS3 models. Our approach is validated by comparisons with observations where we find a good agreement with data. We base our dynamic model on the Müller-Wodarg et al. [2003] general circulation model (GCM) of Titan's thermosphere. Our simulations solve the full non-linear Navier-Stokes momentum equation assuming a realistic thermal structure and lower boundary super-rotation. We find our derived winds are consistent with much of the data between 70-120 km. Solving the full momentum equation we find dynamics below 80km are predominately cyclostrophic. Near 75km we find a good agreement between our GCM, cyclostrophic and cloud tracked winds between 45-85⁰ latitude. Equatorward of 30⁰ cyclostrophic winds decrease steeply with latitude. This is not seen in our GCM winds, which are sustained by an equatorward transport of momentum, neglected in the cyclostrophic approximation. Above 80km we find a balance of advection and pressure gradients replaces cyclostrophic balance poleward of (50-60⁰). Above 75km a pole-to-equator temperature gradient drives equatorward winds with peak speeds of 100ms⁻1 near 95 km, and zonal winds decrease with height. Zonal forcing above 90km drives a reversal in dayside meridional winds and accelerates a subsolar-to-antisolar flow. We find the winds between 90-150km are not characterised by a simple balance of accelerations. Above 150km we find a symmetric subsolar-to-antisolar flow, characterised by a balance of horizontal pressure gradients and viscosity with 200 ms⁻1 cross terminator winds. Our simulations address the origin of the thermospheric super-rotation. We find the cloud top super-rotation does not propagate above 100 km, nor is a super-rotation above 150km driven in situ by our pressure gradients.
13
Yamamoto, Mamoru. "Radar observations of gravity waves in the mesosphere." Kyoto University, 1987. http://hdl.handle.net/2433/74712.
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14
Woithe, Jonathan Mark. "Optical studies of the mesospheric region." Title page, contents and abstract only, 2000. http://web4.library.adelaide.edu.au/theses/09PH/09phw847.pdf.
Texte intégralRésumé :
Includes copies of articles co-authored by the author during the preparation of this thesis. Includes bibliographical references (leaves 233-245). A three-field photometer was employed at the University of Adelaide's Buckland Park field site to collect optical observations of the 557.7nm OI and 730nm OH airglow emissions on an almost continuous basis since May 1995 to May 2000, with observations made whenever the moon was not up.
15
Krug, Amelie, Friederike Lilienthal, and Christoph Jacobi. "The terdiurnal tide in the MUAM circulation model." Universität Leipzig, 2015. https://ul.qucosa.de/id/qucosa%3A16650.
Texte intégralRésumé :
The terdiurnal tide (TDT) in the mesosphere and lower thermosphere has been simulated with a 3D mechanistic circulation model of the middle atmosphere. The tidal temperature amplitude shows a clear seasonal cycle with peaks in the midlatitudes and near the equator at equinox. Under solstice conditions maximum amplitudes occur at 10° in the summer hemisphere and at 30-40° latitude in the winter hemisphere. The vertical wavelengths are large at midlatitudes and small at the equator with about 15 km. These characteristics are compared with SABER/TIMED satellite data from 2002-2009. Especially for temperature amplitudes good agreement is visible. At 90 km, comparison of the zonal wind TDT with radar observations from the literature also shows that the model realistically simulates the seasonal cycle of the TDT.<br>Die achtstündige Gezeit (TDT) in der Mesosphäre und unteren Thermosphäre wurde mit einem 3D mechanistischen Zirkulationsmodell der mittleren Atmosphäre modelliert. Die Amplitude der achtstündigen Gezeit in der Temperatur zeigt dabei eine klare saisonale Variabilität mit Maxima im Bereich der mittleren Breiten und des Äquators während der Äquinoktien. Die vertikale Wellenlänge ist in den mittleren Breiten groß und am Äquator mit ca. 15 km klein. Diese Strukturen werden mit SABER/TIMED Satellitenmessungen der Jahre 2002-2009 verglichen. Vor allem für die Amplituden in der Temperatur ist eine gute Übereinstimmung zu erkennen. Ein Vergleich der achtstündigen Gezeit im Zonalwind in 90 km Höhe mit Radarmessungen aus der Literatur zeigt, dass das Modell den Jahresgang realistisch simuliert.
16
Jacobi, Christoph. "Possible signal of tropospheric circulation patterns in middle atmosphere dynamics, Collm (51.3°N, 13°E) mesosphere lower thermosphere winds: 1979 - 2008." Universität Leipzig, 2009. https://ul.qucosa.de/id/qucosa%3A16368.
Texte intégralRésumé :
Time series of monthly mean Collm mesosphere/lower thermosphere winds 1979 - 2008 are analyses with respect to a possible correlation with North Atlantic Oscillation (NAO) and Southern Oscillation (SO) indices. There is a positive correlation with both indices until the middle 1990s, but later the correlation decreases or even reverses. Owing to the coupling of the SO with the NAO the change of correlation occurs broadly at the same time. The change of correlation is probably connected with changes of the middle atmosphere mean dynamics.<br>Zeitreihen von Monatsmittelwerten des Windes in der Mesosphäre/unteren Thermosphäre über Collm werden auf mögliche Korrelationen mit der Nordatlantischen Oszillation (NAO) und der Südlichen Oszillation (SO) hin untersucht. Während eine positive Korrelation bis in die 1990er Jahre existiert, schwächt sich diese in der Folge ab und kehrt sich teilweise um. Da NAO und SO gekoppelt sind, erfolgen diese Änderungen etwa zur selben Zeit. Die Änderung der Kopplung steht wahrscheinlich in Verbindung mit einer generellen Änderung der Dynamik der mittleren Atmosphäre.
17
Barabash, Victoria. "Investigation of Polar Mesosphere Summer Echoes in Northern Scandinavia." Doctoral thesis, Umeå University, Physics, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-176.
Texte intégralRésumé :
<p>This PhD thesis deals with phenomena which are closely related to the unique thermal structure of the polar summer mesosphere, namely Polar Mesosphere Summer Echoes (PMSE). PMSE are strong radar echoes commonly observed by VHF MST radars from thin layers in the 80-90 km altitude interval at high latitudes during summer. They follow a seasonal pattern of abrupt appearance in late May and a gradual disappearance in mid-August. This period corresponds roughly to the time between the completion of the summer time cooling of the polar mesopause to the time of reversal of the mesospheric circulation to autumn condition. In this connection, PMSE are associated with the extremely low temperatures, i.e. below 140 K, which are unique to the polar summer mesopause. Traditional theories of radar (partial) reflection and scattering have been unable to explain the PMSE and the exact mechanism for their occurrence remains unclear despite the steadily increasing interest in them over the past 20 years. Currently accepted theories regarding the mechanism giving rise to PMSE agree that one of the conditions needed for enhanced radar echoes is the presence of low-mobility charge carries such as large cluster ions and ice aerosols which capture the ambient electrons. It has been established that the PMSE are in some way associated with noctilucent clouds (NLC), layers of ice crystals, which constitute the highest observed clouds in the earth’s atmosphere. PMSE occurrence and dynamics are also found to be closely connected with the planetary and gravity waves.</p><p>Observations of PMSE presented in this thesis have been carried out by the Esrange MST radar (ESRAD) located at Esrange (67°56’N, 21°04’E) just outside Kiruna in northernmost Sweden. The radar operates at 52 MHz with 72 kW peak power and a maximum duty cycle of 5%. The antenna consists of 12x12 array of 5-element Yagis with a 0.7l spacing. During the PMSE measurements the radar used a 16-bit complementary code having a baud length of 1mS. This corresponds to height resolution of 150 m. The sampling frequency was set at 1450 Hz. The covered height range was 80-90 km. The presence of PMSE was determined on the basis of the radar SNR (signal-to-noise ratio). The PMSE measurements have been made during May-August each year since 1997.</p><p>PMSE seasonal and diurnal occurrence rates as well as dynamics have been studied in connection with tidal winds, planetary waves, temperature and water vapor content in the mesosphere (Papers I, IV and VI). Simultaneous and common-volume observations of PMSE and noctilucent clouds have been performed by radar, lidar and CCD camera (Paper V). Correlation between variations in PMSE and variations in extra ionization added by precipitating energetic electrons or high-energy particles from the Sun has been examined (Papers II and III). Possible influence of transport effects due to the electric field on PMSE appearance has been studied during a solar proton event (Paper III).</p>
18
Barabash, Victoria. "Investigation of polar mesosphere summer echoes in northern Scandinavia /." Kiruna : Swedish Institute of Space Physics (Institutet för rymdfysik), 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-176.
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19
Frame, David J. "Wind measurement and momentum balance in the southern mesosphere." Thesis, University of Canterbury. Physics, 1998. http://hdl.handle.net/10092/5938.
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This thesis makes use of diverse data sets in order to develop an understanding of the dynamics of the upper mesosphere in the region near Birdlings Flat, New Zealand.
Medium frequency radar data from the Birdlings Flat site were obtained for the period between May 1993 and December 1996. When analysed, the data reveal two distinct annually varying patterns of circulation, one of which corresponds to seasonal behaviour characteristic of the upper mesospheric, while the other is part of the lower thermospheric climatology. Time-series of wind data in the upper mesosphere also reveal the presence of a feature, recurring each winter, which appears to be the product of breaking gravity waves acting on the mesospheric jet.
Wind data from the Birdlings Flat radar were compared with wind measurements made by the High-Resolution Doppler Imager aboard the Upper Atmosphere Research Satellite. Data from the two instruments were compared on short time-scales and are discussed with reference to a number of physical parameters, especially proximity of measurement, data reliability and the local hour of observation. Although the small number of satellite overpasses limit the reliability of the conclusions of this comparison, proximity was found to be the most relevant of the three features. Data from the two instruments were also compared on longer time-scales with the intention of avoiding tidal contamination in the comparison. Two approaches to this problem are discussed. In one, the overpasses used in the individual comparisons are binned together according to season, while in the other, the longitudinal restriction was lifted from the satellite instrument, and a sampling period corresponding to a full 24 hours of local time was obtained for both the radar and satellite instruments. This approach gave at least as good agreement as the previous methods.
Radar wind data are also compared with wind data derived from the Improved Stratospheric And Mesospheric Sounder for the month of May 1992. The comparison between the two data sets, in conjunction with other material from this thesis, forms the basis of a study of the effects of gravity wave breaking on the momentum budget of the winter mesosphere in the mid-latitude Southern Hemisphere. Even when the maximum likely uncertainty is added to the magnitude of the monthly mean radar winds, there is still a significant discrepancy between observed and derived winds. This appears as unresolved-scale forcing terms in the atmospheric momentum equations. The unresolved-scale term in the zonal momentum equation is due primarily to the effects of breaking gravity waves, and was calculated to be D = 80 ± 40 ms-1d-1. The large and highly variable value of the unresolved-scale term in the meridional momentum equation, E = 88 ± 120 ms-1d-1 is more complicated, but is likely to incorporate a large contribution from the inter-play of various small-scale curvature terms.
20
Nakamura, Takuji. "Mesosphere and Lower Thermosphere Dynamics Revealed by Radar Observations." Kyoto University, 1991. http://hdl.handle.net/2433/74598.
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21
Chu, Ding-Chong Allen. "The interpretation of SAGE II ozone measurements in the lower mesosphere." Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/26221.
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22
Jacobi, Christoph, and Manfred Ern. "Gravity waves and vertical shear of zonal wind in the summer mesosphere-lower thermosphere." Universität Leipzig, 2013. https://ul.qucosa.de/id/qucosa%3A16408.
Texte intégralRésumé :
Gravity wave amplitudes and momentum fluxes derived from SABER temperature measurements are analysed together with Collm meteor radar zonal winds. The momentum flux (MF) divergence derived from the SABER temperatures shows a maximum that is found at greater altitudes during solar minimum than during solar maximum. Therefore, the zonal mean wind and wind shear profiles are shifted upwards
then, leading to a modulation of the otherwise negative correlation between solar cycle and mesosphere/lower thermosphere winds.<br>Amplituden von Schwerewellen und zugehörigen Impulsflüsse werden zusammen mit Windmessungen des Meteorradars Collm analysiert. Die Impulsflussdivergenz, abgeleitet aus SABER-Temperaturprofilen, hat ein Maximum welches im solaren Minimum nach oben verschoben ist. Dadurch werden auch die Vertikalprofile des Zonalwindes und der Windscherung nach oben verschoben, wodurch die ansonsten negative Sonnenfleckenzyklusabhängigkeit des zonalen Windes in der Mesosphäre/unteren
Thermosphäre im solaren Minimum umgekehrt wird.
23
Hultgren, Kristoffer. "Tomographic views of the middle atmosphere from a satellite platform." Doctoral thesis, Stockholms universitet, Meteorologiska institutionen (MISU), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-106833.
Texte intégralRésumé :
The middle atmosphere is a very important part of the Earth system. Until recently, we did not realize the importance of the structure of this vaporous shell and of the fundamental role it plays in both creating and sustaining life on the planet. Thanks to the development and improvement of new sounding methods and techniques, our knowledge of the composition of the atmosphere has become more detailed than ever before. We have also learned how to reveal complex interactions between different species and how they react to the incoming solar radiation. The middle part of the Earth’s atmosphere serves as a host for the Polar Mesospheric Clouds. These clouds consist of a thin layer of water-ice particles, only exsisting during the summer months and only close to the poles. There are indications that the occurrence of Polar Mesospheric Clouds may be linked to climate change. It has been pointed out that the first sightings coincide with the industrial revolution. Satellite observations have shown that Polar Mesospheric Clouds have become brighter and possibly more widely distributed during the 20th century. The clouds might therefore be suited as indicators of the variability of the climate - a good reason for studying this night-shimmering phenomena. The clouds can also be used as a proxy for middle atmospheric dynamics. In order to fully utilize Polar Mesospheric Clouds as tracers for atmospheric variability and dynamics, we need to better understand their local properties. The Optical Spectrograph and Infra-Red Imager System (OSIRIS) is one of two instruments installed on the Odin satellite. The optical spectrograph of this instrument observes sunlight scattered by the atmosphere and thus the Polar Mesospheric Clouds. This thesis deals with a tomographic technique that can reconstruct both horizontal and vertical structures of the clouds by using observations from various angles of the atmospheric region. From this information, microphysical properties such as particle sizes and number densities are obtained. The tomographic technique presented in this thesis also provides a basis for a new satellite concept - MATS. The idea behind the MATS satellite mission is to analyze wave activity in the atmosphere over a wide range of spatial and temporal scales, based on the scientific heritage from Odin/OSIRIS and the tomographic algorithms presented in this thesis.<br><p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper3: Submitted. Paper 4: Manuscript.</p>
24
Harris, Trevor. "Large-scale dynamics of the upper mesosphere and lower thermosphere /." Title page, contents and abstract only, 1993. http://web4.library.adelaide.edu.au/theses/09PH/09phh3165.pdf.
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Tjelle, Erlend Magnus. "Mesoscale gravity wave activity in the Mesosphere over Northern-Norway." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-26135.
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The purpose of this study is to examine wind data retrieved from the SKiYMET-radarsat Trondheim and Andenes during the time period of the 27th of November to the 02ndof December 2012. These dates surrounds the night between the 29th-30th of November,were Hennum (2013) discovered large scale fluctuations in the hydroxyl layer dueto gravity wave activity over Trondheim. Similar fluctuations where found over Andenes(although not mentioned in Hennum's thesis), providing for the possibility of a mesoscale connected gravity wave system with wavefronts stretching over 700 km in the middle atmosphere.The analyses of the wind data results in a significant correlation for the mean zonal and meridional anomalies over Andenes and Trondheim. Further, balloon soundings duringthe period show that the Scandinavian mountain range does not seem to be the source,but rather a large scale moving frontal wave system, or shear waves.
26
Fan, Zeyu. "Satellite retrievals of the global sodium layer in the mesosphere." Thesis, University of East Anglia, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.433788.
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Day, Kerry. "Planetary wave dynamics of the stratosphere, mesosphere and lower thermosphere." Thesis, University of Bath, 2011. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.547637.
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28
Lange, Martin, and Christoph Jacobi. "Einfluß des winterlichen stratosphärischen Polarwirbels auf die zonale Symmetrie des Windfeldes in der oberen Mesosphäre und unteren Thermosphäre simuliert mit dem COMMA-Modell: Einfluß des winterlichen stratosphärischen Polarwirbels auf die zonale Symmetrie des Windfeldes in der oberen Mesosphäre und unteren Thermosphäresimuliert mit dem COMMA-Modell." Wissenschaftliche Mitteilungen des Leipziger Instituts für Meteorologie ; 22 = Meteorologische Arbeiten aus Leipzig ; 6 (2001), S. 111-120, 2001. https://ul.qucosa.de/id/qucosa%3A15212.
Texte intégralRésumé :
Langzeitmessungen des Windfeldes in der Mesopausenregion (~ 92km) an verschiedenen Stationen in den mittleren Breiten der Nordhemisphäre zeigen systematische zonale Variationen beim (zeitlich) gemittelten Zonal- und Meridionalwind und bei den Amplituden
und Phasen der halbtägigen Gezeiten. Als eines der herausragenden Muster, die zonale Variationen in der unteren mittleren Atmosphäre anregen, wird der Einfluß der Geopotentialstörungen zur zonalen Wellenzahl 1 und 2, die mit dem winterlichen stratosphärischen Polarwirbel verbunden sind, auf das Windfeld in der oberen Mesosphäre / unteren Thermosphäre numerisch mit dem COMMA-Modell der mittleren Atmosphäre untersucht. Die Modellergebnisse zeigen eine gute Übereinstimmung der zonalen Variationen des mittleren Zonalwindes, die im Breitenbereich 52ÆN bis 56ÆN beobachtet werden und in der Größenordnung von 10 - 20 m/s liegen. Auch die halbtägigen Gezeitenamplituden und -phasen zeigen qualitative und quantitative Übereinstimmungen zwischen Beobachtungen und Modellergebnissen.<br>Long-term time series of wind field observations in the upper mesosphere / lower thermosphere region at different locations in the midlatitude region indicate longitudinal variability in the (time-) mean zonal and meridional wind and in the amplitudes and phases of the semidiurnal tide, too. Being one of the prominent patterns forcing zonal
inhomogenities in the lower middle atmosphere, the influence of the zonal wavenumber 1 and wavenumber 2 disturbances connected with the winter Northern Hemisphere stratospheric polar vortex on the mesosphere- / lower thermosphere wind field is numerically investigated with the COMMA model. The model results show that the zonal variations through the stationary waves coincide with typical observed mean zonal wind differences between different stations along the midlatitude belt between 52ÆN and 56ÆN with values about 10- 20 m/s. Also, the amplitude and phase variations of the semidiurnal tide show qualitative and quantitative agreements between model results and observations.
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Allgood, Michael David Baginski Michael E. "Finite element analysis of the mesosphere's electromagnetic response to large scale lightning associated with sprites and other transient luminous events." Auburn, Ala, 2008. http://repo.lib.auburn.edu/EtdRoot/2008/SPRING/Electrical_and_Computer_Engineering/Thesis/Allgood_Michael_37.pdf.
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Cox, Rachel Mary. "On the origin of sporadic neutral sodium layers." Thesis, University of East Anglia, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365136.
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Smith, Steven Michael. "Optical and radar wind comparisons in the mesosphere and lower thermosphere." Thesis, University of Canterbury. Physics, 1996. http://hdl.handle.net/10092/8159.
Texte intégralRésumé :
This project involved the comparison of horizontal winds in the upper mesosphere at 80-105 km which were obtained by two different ground-based techniques located in Canterbury. Optical Doppler winds were derived from night time observations of the mesospheric 557.7 nm airglow emission near 95 km (FWHM intensity ∼10-12 km) using a Fabry-Perot Spectrometer (FPS) during the period February 1991 to July 1994. These were compared to simultaneous radar winds obtained using a partial-reflection MF (2.4 MHz) wind-profiling radar. The comparisons were made on 103 nights considered suitable by exhibiting no cloud and low magnetic activity (low Kp) in order to eliminate the possibility of auroral contamination in the FPS measurements.
The results of the FPS/radar wind comparisons were of limited success due to the significant effect of RF noise associated with the radar wind measurements. The meridional optical/radar wind comparisons produced more consistent results than the zonal wind comparisons.
The distribution of daily mean radar wind vectors for all 103 days was aligned perpendicular to the direction of the magnetic meridian. This indicates that the radar winds at 85-105 km are possibly under partial geomagnetic control.
The mean height of best agreement from the cross-correlations between the night time FPS and radar hourly mean winds was 95.8 km with a standard deviation of 6.4 km. This height is agrees closely with the average height of 95.2 km obtained from studies of (satellite) WINDII 557.7 nm emission data. In a second comparison of simultaneous hourly FPS and radar winds, observations averaged over several nights during March/ April 1993 were compared with a mean 557.7 nm emission height profile at 44°S from WINDII data for March/ April. There was good agreement between the FPS and radar hourly winds height in the 88-96 km height region, with best agreement at 92 km.
In an alternative, best agreement between the comparison of phase of the semidiurnal tide fitted to the optical and radar winds was found to occur in the 100-105 km height region.
The amplitudes of the semi-diurnal tide as exhibited in the optical and radar wind fields were investigated and the optical tidal amplitudes were generally larger than the corresponding radar amplitudes. The median optical/radar semi-diurnal amplitude at a height of 95 km was 1.4 with a lower and upper quartile values of 1.0 and 2.5, respectively. The amplitude discrepancy was largest near 95 km.
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Tunbridge, Victoria. "2-day planetary waves in the stratosphere, mesosphere and lower thermosphere." Thesis, University of Bath, 2011. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.538116.
Texte intégralRésumé :
This thesis presents observations of the 2-day planetary wave in the stratosphere, mesosphere and lower thermosphere. These observations were made using two ground-based meteor radars at polar latitudes and the satellite-borne microwave limb sounder (MLS) on the NASA Aura satellite. There have been relatively few observations of the 2-day wave at polar latitudes made using ground-based radars. This is particularly so in the Antarctic. Measurements of summertime and wintertime polar 2-day waves in the mesosphere and lower thermosphere (MLT) region were made using identical meteor radars at the conjugate geographical latitudes of Rothera (68!S, 68!W) in the Antarctic and Esrange (68!N, 21!E) in Arctic Sweden. This allows accurate quantification of the differences in the nature and seasonal variability of the 2day wave between the two polar regions. A clear seasonal variability is evident with the maximum amplitudes occurring during the summer months in both hemispheres. However, significant differences are found in the behaviour of the summertime wave between the two polar regions. In particular, wave activity is shorter lived but of larger amplitude in the Antarctic. These differences are suggested to be partly due to the different background winds of the two polar regions and possible differences in the component zonal wavenumbers in the northern and southern hemispheres. These radar studies have excellent spatial, height and time resolution but cannot resolve the component zonal wavenumbers of the 2-day wave. Therefore, Earth Observing System (EOS) Aura Microwave Limb Sounder (MLS) measurements of atmospheric temperature were used to investigate the climatology and interhemispheric differences of the different zonal wavenumbers (westward propagating zonal wavenumbers 2, 3 and 4) that compose the 2-day wave “complex”. This study demonstrates that the wave is dominated by different wavenumbers in the northern and southern hemisphere and that some of the interhemispheric differences observed in ground-based studies can be explained by the seasonal variability of these different zonal wavenumbers. These satellite studies led to participation in a multi-technique international collaboration to study the short-term variability of the summertime 2-day wave. Observations made in the northern hemisphere at mid-latitudes revealed that there are typically three peaks of enhanced 2-day wave amplitude during the summer, probably originating from a combination of baroclinic instability and critical wind speed.
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Liu, R. Q., and Ch Jacobi. "Piecewise linear trend detection in mesosphere/lower thermosphere wind time series." Universität Leipzig, 2010. https://ul.qucosa.de/id/qucosa%3A16361.
Texte intégralRésumé :
A piecewise linear model is developed to detect climatic trends and possible structural changes in time series with a priori unknown number and positions of breakpoints. The initial noise is allowed to be interpreted by the first- and second-order autoregressive models. The goodness of fit of candidate models, if the residuals are accepted as normally distributed white noise, is evaluated using the Schwarz Bayesian Information Criterion. The uncertainties of all modeled trend parameters are estimated using the Monte-Carlo method. The model is applied to the mesosphere/lower thermosphere winds obtained at Collm (52°N, 15°E) during 1960-2007. A persistent increase after ~1980 is observed in the annual mean zonal wind based on the primary model while only a weak positive trend arises in the meridional component. Major trend breakpoints are identified around 1968-71 and 1976-79 in both the zonal and meridional winds.
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Younger, Peter Thomas. "Radar studies of the dynamics of the mesosphere and lower thermosphere." Thesis, University of Bath, 2004. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487553.
Texte intégralRésumé :
Meteor radars are powerful tools for the study of the atmosphere at heights between -80-100 lan. These heights span the boundary between the mesosphere and the lower thermosphere (MLT) and include the temperature rp.inimum of the mesopause - the coldest naturally occurring place on Earth. This thesis describes studies made using two modem VHF meteor radars. The first was installed at Esrange (68°N, 21°E) in Arctic Sweden in October 1999. The second was deployed on Ascension Island (80 S, 14°W) in the equatorial Atlantic in May 2001. The work is in three parts. The first part is a study of the behaviour of the 8-hour tide at Arctic latitudes undertaken with the Esrange meteor radar. The tide is found to be a persistent feature of the Arctic MLT region and, at times, its amplitude can exceed that of the 24-hour tide. This study investigates the possible excitation mechanisms of this tide - proposals for which have included either direct thermal excitation or non-linear coupling between the 12- and 24-hour tides. The results suggest that, at least some ofthe time, non-linear interactions may contribute to the excitation ofthe tide. The second part uses one year of data from the Ascension Island radar to construct a simple climatology of the mean winds and 12- and 24-hour tides in the equatorial region. The mean winds reveal the clear signature ofthe planetary-scale Dobson-Brewer circulation. Comparisons with simultaneous observations made at higher latitudes suggest that the circulation may contain significant longitudinal structure. The tides are found to be a major part of the MLT-region motion field over Ascension Island. Comparisons with the NCAR HAO Global Scale Wave Model and equatorial observations of tides made elsewhere reveal a number of significant differences and points to the potential importance of non-migrating tides. The final part investigates the planetary-wave field in the MLT region over Ascension Island. A rich and varied field ofplanetary waves is evident. Detailed studies address the quasi-two-day wave, ultra-fast Kelvin waves with periods near three days and the 16day wave. The seasonal behaviour and variability of each type of wave is delineated. Observations of ultra-fast Kelvin waves suggest that the effects of inertia-gravity waves must be considered in the analysis ofsuch waves.
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Schminder, Rudolf. "Die Entwicklung des Arbeitsgebietes Physik der Hochatmosphäre am Geophysikalischen Obsenratorium Collm." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-212298.
Texte intégralRésumé :
Am Geophysikalischen Observatorium Collm, das 1932 als experimentelle Basis des Geophysikalischen Institutes der Universität Leipzig für meteorologische, seismologische und geomagnetische Messungen von Professor LUDWIG WEICKMANN errichtet worden war, wurde 1956 in Vorbereitung des Internationalen Geophysikalischen Jahres (International Geophysical Year [IGY]) mit hochattnosphärischen Messungen begonnen. Seit 1959 liegt der Schwerpunkt auf Windmessungen im Höhenbereich der oberen Mesosphäre / unteren Thermosphäre (80 - 110 km). Die Meß- und Auswertemethode wurde in den vergangenen Jahrzehnten aus sehr bescheidenen Anfängen heraus theoretisch und experimentell so entwickelt, daß derzeit eine vollautomatische komplexe Apparatur zur quasi-kontinuierlichen Windmessung in drei Referenzpunkten über Mitteleuropa (gegenseitige Entfernung 200 km) zur Verfügung steht, die die Momentanwerte des Windes nach Richtung und Geschwindigkeit mißt, die zugehörige Höhe feststellt, Mittelwerte bildet, Grund- und Gezeitenwind voneinander trennt und Höhen-Wind-Profile über vorgebbare Zeitabschnitte rechnet, aus denen letztendlich Höhen-Zeit-Schnitte der Windfeldparameter konstruiert werden können. Die vorliegende Arbeit skizziert die einzelnen Etappen dieser Entwicklung, berichtet von Problemen und ihrer Lösung und gibt Beispiele von Windfeldanalysen aus dem Jahre 1992<br>The Collm Geophysical Observatory was founded by Professor L. WEICKMANN in 1932 as an experimental base of Leipzig University's Geophysical Institute for meteorological, seismological and geomagnetic observations. In 1956 as a preparation for the Internal Geophysical Year (IGY) we began with high-atmosphere measurements, and since 1959 wind measurements in the height range of the upper mesosphere / lower thennosphere (80 - 110 km) have been emphasized. During the past decades the method of measuring and analysing was developped theoretically and experimentally from primitive Starts so far, that at present a fully automatic and complex equipment with quasi-continuous measurements of the wind at three reference points within Central Europe (mutual distance 200 km) is available. These devices measure the instantaneous data of the wind according to direction and velocity, ascertain the corresponding height, calculate averages, separate the tidal wind components from the prevailing wind, and compute height wind-profiles for adjustable periods of time, from which height-time cross section of the wind field parameters can be finally constructed. The following paper outlines the particular stages of this development, informs about problems and their solution, and offers examples of wind field analyses for 1992
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Stevens, M. H., D. E. Siskind, J. S. Evans, S. K. Jain, N. M. Schneider, J. Deighan, A. I. F. Stewart, et al. "Martian mesospheric cloud observations by IUVS on MAVEN: Thermal tides coupled to the upper atmosphere." AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/624978.
Texte intégralRésumé :
We report observations of Martian mesospheric ice clouds and thermospheric scale heights by the Imaging Ultraviolet Spectrograph on NASA's Mars Atmosphere and Volatile Evolution mission. The clouds are observed between 6A.M. and 8A.M. local time using mid-UV limb observations between 60 and 80km tangent altitude where ice particles that scatter sunlight can appear as detached layers near the equator. The equatorial longitudinal distribution shows populations of clouds near -110 degrees E and -10 degrees E as well as a population near 90 degrees E, which does not have a clear precedent. The cloud populations indicate a wave 3 pattern near 70km, which is confirmed by independent mesospheric temperature observations. Scale heights 100km above the clouds derived from concurrent Imaging Ultraviolet Spectrograph (IUVS) observations also reveal a wave 3 longitudinal structure, suggesting that the temperature oscillations enabling the formation of mesospheric clouds couple to the upper atmosphere. Plain Language Summary The manuscript describes the observation of Martian mesospheric clouds between 60 and 80km altitude by the Imaging Ultraviolet Spectrograph (IUVS) on NASA's MAVEN spacecraft. The cloud observations are uniquely obtained at early morning local times, which complement previous observations obtained primarily later in the diurnal cycle. Differences in the geographic distribution of the clouds from IUVS observations indicate that the local time is crucial for the interpretation of mesospheric cloud formation. We also report concurrent observations of upper atmospheric scale heights near 170 km altitude, which are diagnostic of temperature. These observations suggest that the dynamics enabling the formation of mesospheric clouds propagate all the way to the upper atmosphere.
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Igarashi, Kiyoshi. "MF radar studies on the dynamics of the mesosphere and lower thermosphere." 京都大学 (Kyoto University), 2006. http://hdl.handle.net/2433/135950.
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Samtleben, Nadja, and Christoph Jacobi. "Long-period oscillations derived from mesosphere/lower thermosphere meteor radar temperature measurements." Universität Leipzig, 2015. https://ul.qucosa.de/id/qucosa%3A16649.
Texte intégralRésumé :
Using measurements, derived from a meteor radar in Collm (51.3°N, 13°E), the mesopause region is analyzed with respect to the temperature distribution at an altitude of 90 km over a period of 10 years. The analyzed period lasts from 2005 till 2013. Based on these measurements, the typical temperature seasonal cycle of the mesopause region can be observed. The temperature reaches its minimum of about 130 K in summer and its maximum of about 220 K in winter. At this altitude, also strong day-today- fluctuations of up to 35 K exist, which are probably partly induced by planetary waves. Shorter-period oscillations with a period between 2 and 6 days have maximum amplitudes during summer, while longer-period oscillations with a period between 7 and 20 days maximize during winter. During the measurement period the amplitudes of oscillations with periods between 4 and 6 days, which may be attributed to the quasi-5-day-wave, increase with time.<br>Auf der Grundlage von Messungen eines Meteorradars in Collm (51.3°N, 13°E), die in einer Höhe von 90 km erfolgten, was in etwa der Mesopause entspricht, wird die Temperatur hinsichtlich ihres Jahresganges und insbesondere ihrer Variationen in einem Messzeitraum von 10 Jahren analysiert. Der analysierte Zeitraum erstreckt sich von 2005 bis 2013. Anhand der Daten kann man den typischen Jahresgang der Temperatur in der Mesopausenregion erkennen. Die Temperatur erreicht im Sommer das Minimum bei etwa 130 K und im Winter das Maximum bei etwa 220 K. Zudem treten starke Tag-zu-Tag-Fluktuationen auf, die im Maximum 35 K betragen. Diese werden vermutlich durch planetare Wellenaktivität der Atmosphäre hervorgerufen. Hierbei spielen im Sommer die kurzwelligen und im Winter die langwelligen Oszillationen, letztere mit Perioden größer 7 Tage, die wesentliche Rolle. Ferner sind innerhalb des Messzeitraums zunehmende Amplituden von Oszillationen mit Perioden zwischen 4 und 6 Tagen (quasi 5-Tage-Welle) zu erkennen.
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Jacobi, Christoph, Friederike Liilienthal, T. Schmidt, and la Torre A. de. "Modeling the Southern Hemisphere winter circulation using realistic zonal mean gravity wave information in the lower atmosphere." Universität Leipzig, 2016. https://ul.qucosa.de/id/qucosa%3A16703.
Texte intégralRésumé :
A mechanistic global circulation model is used to simulate the mesospheric and lower thermospheric circulation during austral winter. The model includes a gravity wave (GW) parameterization that is initiated by prescribed GW parameters in the troposphere. In standard configuration, these waves are described by a simple distribution with large amplitudes in the winter hemisphere and small ones in summer. Here we replace this distribution by a more realistic one, which is based on observations of potential GW energy using GPS radio occultations, but which is normalized to the same global mean amplitude. The model experiment shows that this new gravity wave distribution leads to weaker zonal winds in the mesosphere, a downward shift of the meridional poleward mesospheric wind jet, enhanced downwelling in the mid-to-high-latitude winter mesosphere and warming of the polar stratopause.<br>Ein globales mechanistisches Zirkulationsmodell wird verwendet um die Dynamik der Mesosphäre und unteren Thermosphäre im Südwinter zu simulieren. Das Modell beinhaltet eine Schwerewellenparametrisierung die durch eine vorgeschriebene Schwerewellenverteilung in der oberen Troposphäre angetrieben wird. In der Standardkonfiguration besteht diese aus einer einfachen zonal gemittelten Verteilung mit größeren Amplituden im Winter als im Sommer. Wir ersetzen diese Verteilung durch eine realistischere, die auf der beobachteten globalen Verteilung der potentiellen Energie von Schwerewellen basiert und auf die gleiche global gemittelte Amplitude normiert wird. Das Modellexperiment zeigt, dass die neue Schwerewellenverteilung zu schwächeren zonalen Winden in der Mesosphäre, einer Verschiebung des meridionalen Jets nach unten, verstärkten Abwinden in der Mesosphäre mittlerer und höherer Breiten im Winter, und einer Erwärmung der polaren Winterstratopause führt.
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Smirnova, Maria. "Long-term observations of polar mesosphere summer echoes using the ESRAD MST radar." Doctoral thesis, Luleå tekniska universitet, Rymdteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18134.
Texte intégralRésumé :
Polar Mesosphere Summer Echoes (PMSE) are strong radar echoes observed from altitudes of 80-90 km in polar regions, during summer time. PMSE are closely related to the fascinating atmospheric phenomenon known as noctilucent clouds (NLC). Since it has been suspected that NLC could respond to climate change in the mesosphere, they have attracted considerable interest in the scientific community during recent years. However, continuous visual or photographic NLC observations suffer from weather restrictions and the human factor. In contrast, PMSE radar measurements can easily be made over a long interval and are very attractive for long-term studies of the atmospheric parameters at the polar mesopause. This thesis uses the world’s longest data set of PMSE observations made by the same radar at the same place. Since 1997 these measurements have been carried out with the 52 MHz ESRAD MST radar located near Kiruna in Northern Sweden. The data set for 1997-2008 has been used for studies of diurnal, day-to-day and year-to-year variations of PMSE. We showed that PMSE occurrence rate and volume reflectivity on a daily scale show predominantly semidiurnal variations with the shape of the diurnal curves remaining consistent from year to year. We found that day-to-day and inter-annual variations of PMSE correlate with geomagnetic activity while they do not correlate with mesopause temperature or solar activity. We did not find any statistically significant trends in PMSE occurrence rate and length of PMSE season over 1997-2008. The thesis also presents also a new, independent calibration method, which can be used to estimate changes in transmitter output and antenna feed losses from year to year (for example due to changes of antenna configuration) and allows making accurate calculations of PMSE strength. This method is based on radar-radiosonde comparisons in the upper troposphere/lower stratosphere region simultaneously with PMSE observations. Using this calibration we calculated the distribution of PMSE strength over magnitudes; it varies from year to year with the peak of the distribution varying from 2×10−15 to 3×10−14 m−1. We found that inter-annual variations of PMSE volume reflectivity strongly correlate with the local geomagnetic k-index and anticorrelate with solar 10.7 cm flux. We did not identify any significant trend in PMSE volume reflectivity over 1997–2009. Finally, using 11 years of measurements, we calculated in-beam the PMSE aspect sensitivities using the FCA technique. We showed that half of PMSE detected each year cannot be explained by isotropic turbulence since they are highly aspect sensitive echoes. The distribution of these echoes remains consistent from year to year with median values of aspect sensitivity from 2.9 to 3.7°. The remaining half of the PMSE have aspect sensitivity parameters larger than 9-11°. We found that PMSE aspect sensitivity has altitude dependence: the scatter becomes more isotropic with increasing height. We did not identify any dependence of PMSE aspect sensitivity on backscattered power for any year. We analysed limitations of the in-beam and off-zenith beam methods and concluded that the former is suitable for highly aspect sensitive echoes while the latter is needed for more isotropic scatterers.<br><p>Godkänd; 2011; 20110926 (marsmi); DISPUTATION Ämnesområde: Rymdteknik/Space Technology Opponent: Professor Patrick Joseph Espy, Dep of Physics, Norwegian University of Science and Technology (NTNU), Trondheim, Norway, Ordförande: Docent Evgenia Belova, Swedish Institute of Spaces Physics, Kiruna Tid: Måndag den 31 oktober 2011, kl 10.00 Plats: Aulan, Swedish Institute of Spaces Physics, Kiruna</p>
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Wilms, Henrike [Verfasser], and Markus [Akademischer Betreuer] Rapp. "Microphysics of ice particles in the polar summer mesosphere / Henrike Wilms ; Betreuer: Markus Rapp." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2016. http://d-nb.info/1119073677/34.
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Jacobi, Christoph, and Dierk Kürschner. "A possible connection of midlatitude mesosphere/lower thermosphere zonal winds and the Southern oscillation." Universitätsbibliothek Leipzig, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-216880.
Texte intégralRésumé :
Collm (52°N, 15°E) midlatitude mesosphere/lower thermosphere (MLT) zonal winds are investigated with respect to a possible influence of the Southern Oscillation (SO). It is found that in winter the prevailing wind is positively correlated with the Southern Oscillation index (SOI), which qualitatively fits to the response of the low-latitude stratosphere on the SO. In summer, however, there is a negative correlation between MLT zonal winds and SOI. A possible mechanism, which includes slightly enhanced planetary wave propagation to the MLT in summers of low SOI is discussed<br>Windmessungen aus Collm (52°N, 15°E) wurden hinsichtlich eines möglichen Einflusses der Southern Oscillation (SO) in ihnen untersucht. Es zeigt sich, dass im Winter der mittlere Zonalwind positiv mit dem \"Southern Oscillation Index\" SOI korreliert ist, was qualitativ mit der Reaktion der Stratosphäre auf ENSO übereinstimmt. Im Sommer findet sich jedoch ein negativer Zusammenhang zwischen hochatmosphärischem Zonalwind und SOI. Ein möglicher Mechanismus, der die Ausbreitung planetarer Wellen beinhaltet, wird diskutiert
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Jacobi, Christoph, and Dierk Kürschner. "A possible connection of midlatitude mesosphere/lower thermosphere zonal winds and the Southern oscillation." Wissenschaftliche Mitteilungen des Leipziger Instituts für Meteorologie ; 22 = Meteorologische Arbeiten aus Leipzig ; 6 (2001), S. 98-110, 2001. https://ul.qucosa.de/id/qucosa%3A15211.
Texte intégralRésumé :
Collm (52°N, 15°E) midlatitude mesosphere/lower thermosphere (MLT) zonal winds are investigated with respect to a possible influence of the Southern Oscillation (SO). It is found that in winter the prevailing wind is positively correlated with the Southern Oscillation index (SOI), which qualitatively fits to the response of the low-latitude stratosphere on the SO. In summer, however, there is a negative correlation between MLT zonal winds and SOI. A possible mechanism, which includes slightly enhanced planetary wave propagation to the MLT in summers of low SOI is discussed.<br>Windmessungen aus Collm (52°N, 15°E) wurden hinsichtlich eines möglichen Einflusses der Southern Oscillation (SO) in ihnen untersucht. Es zeigt sich, dass im Winter der mittlere Zonalwind positiv mit dem \"Southern Oscillation Index\" SOI korreliert ist, was qualitativ mit der
Reaktion der Stratosphäre auf ENSO übereinstimmt. Im Sommer findet sich jedoch ein negativer Zusammenhang zwischen hochatmosphärischem Zonalwind und SOI. Ein möglicher Mechanismus, der die Ausbreitung planetarer Wellen beinhaltet, wird diskutiert.
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Bardeen, Charles Gaylord. "Three-dimensional numerical simulations of clouds and aerosols in the mesosphere using WACCM/CARMA." Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3337072.
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Cuevas, Brian J. "Synthesis and properties of protein micro/mesosphere-drug compositions designed for intratumoral cancer therapy." [Gainesville, Fla.] : University of Florida, 2003. http://purl.fcla.edu/fcla/etd/UFE0001106.
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Narayanan, V. Lakshmi. "Study of dynamical coupling of the mesosphere-lower thermosphere-ionosphere region at low latitudes." Thesis, Indian Institute of Geomagnetism, Mumbai, 2011. http://localhost:8080/xmlui/handle/123456789/223.
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Jacobi, Christoph, Peter Hoffmann, and Dierk Kürschner. "Trends and climatic shifts in mesosphere / lower thermosphere planetary waves Collm (52°N, 15°E)." Universität Leipzig, 2007. https://ul.qucosa.de/id/qucosa%3A15567.
Texte intégralRésumé :
Long-period oscillations in the period range between 2-30 days, interpreted as planetary wave (PW) signatures, have been analysed using daily upper mesosphere/lower thermosphere wind measurements near 90 km over Collm (52°N, 15°E) in the time interval 1980-2005. Strong interannual and interdecadal variability of PW are found. Since the 1990s, a tendency for larger zonal amplitudes compared to meridional ones, has been observed, thus long-term trends are visible, which are positive in the zonal component, but negative in the meridional component. The change appears in a stepwise manner, so that a sudden change of the mean is visible rather than a linear trend. The behaviour of the upper middle atmosphere winds is similar to analysed wave changes in the stratosphere, indicating a coupling of the atmospheric layers through planetary waves.<br>Mit Hilfe von täglichen Windmessungen im Mesopausenbereich bei 90 km werden langperiodische Schwankungen im Zeitbereich von 2-30 Tagen untersucht, die als das Signal planetarer Wellen gelten. Im Zeitraum 1980-2005 werden deutliche Schwankungen von Jahr zu Jahr als auch langfristige Trends gefunden. Einer Zunahme der zonalen Komponente der Schwankungen seit 1990 steht eine Abnahme der meridionalen Komponente gegenüber. Diese Änderung erfolgt in rascher Form, so dass sich die Änderung der Zirkulation im Mesopausenbereich als klimatische Verschiebung, und weniger als Trend darstellt. Das Verhalten der Dynamik im Mesopausenbereich korrespondiert mit möglichen Änderungen klimatischer Parameter in anderen Schichten der Atmosphäre und weist auf eine Kopplung atmosphärischer Schichten untereinander hin.
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Chen, Chen. "Electron Temperature Enhancement Effects on Plasma Irregularities Associated with Charged Dust in the Earth's Mesosphere." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/25937.
Texte intégralRésumé :
Recently, experimental observations have shown that Polar Mesospheric Summer Echoes PMSE may be modulated by radio wave heating the irregularity source region with a ground-based ionospheric heating facilities. It is clear from these past
investigations that the temporal behavior of PMSE during ionospheric heating shows promise as a diagnostic for the associated dust layer. To investigate the temporal behavior of plasma irregularities thought to produce PMSE, this work describes a new model that incorporates both finite diffusion time effects as well as dust charging. The hybrid model utilizes fluid ions described by continuity and momentum equations, electrons whose behavior is determined from quasi-neutrality, and charged dust described by the standard Particle-In-Cell PIC method. The model has been used to investigate the temporal behavior of charged dust associated electron irregularities during electron temperature enhancement associated with radio wave heating. The model predicts that the temporal behavior of the irregularities depends on the ratio
of the electron-ion ambipolar diffusion time to the dust particle charging time Td/Tc. The results indicate that typically for Td/Tc << 1, an enhancement in electron irregularity amplitude occurs for a period after turn-off of the radio wave heating. The work also predicts that for Td/Tc >> 1, an enhancement in electron irregularity amplitude occurs for a time period after the turn-on of the radio wave heating. Due to the dependence of Td on irregularity scale-size, these results have important implications
for observations of PMSE modification at different radar frequencies. Both continuous and discrete charging model were embedded into this computational model, the results were compared and analyzed.
It is evident that significant diagnostic information may be available about the dust
layer from the temporal behavior of the electron irregularities during the heating process which modifies the background electron temperature. Particularly interesting and important periods of the temporal behavior are during the turn-on and turn-off of the radio wave heating. Although a number of past theoretical and experimental
investigations have considered both these on and off period, this dissertation considers further possibilities for diagnostic information available as well as the underlying physical processes. Approximate analytical models are developed and compared to a more accurate full computational model as a reference. Then from the temporal behavior of the electron irregularities during the turn-on and turn-off of the radio wave
heating, the analytical models are used to obtain possible diagnostic information for various charged dust and background plasma quantities.
Finally, two experiment campaigns have been performed at HAARP, Gakona, Alaska. Preliminary observation results look promising for the existence of PMSE turn-on overshoot. However, more careful experiments need to be done before firm conclusions can be drawn. The new designed Echotek digital receiver is ready for use now. It will be much superior to the experimental setup used for measurements in the previous campaign.Therefore, future experimental campaigns are planning next year to support the theoretical research.<br>Ph. D.
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Jacobi, Christoph, Peter Hoffmann, and Dierk Kürschner. "Trends and climatic shifts in mesosphere / lower thermosphere planetary waves Collm (52°N, 15°E)." Universitätsbibliothek Leipzig, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-223160.
Texte intégralRésumé :
Long-period oscillations in the period range between 2-30 days, interpreted as planetary wave (PW) signatures, have been analysed using daily upper mesosphere/lower thermosphere wind measurements near 90 km over Collm (52°N, 15°E) in the time interval 1980-2005. Strong interannual and interdecadal variability of PW are found. Since the 1990s, a tendency for larger zonal amplitudes compared to meridional ones, has been observed, thus long-term trends are visible, which are positive in the zonal component, but negative in the meridional component. The change appears in a stepwise manner, so that a sudden change of the mean is visible rather than a linear trend. The behaviour of the upper middle atmosphere winds is similar to analysed wave changes in the stratosphere, indicating a coupling of the atmospheric layers through planetary waves<br>Mit Hilfe von täglichen Windmessungen im Mesopausenbereich bei 90 km werden langperiodische Schwankungen im Zeitbereich von 2-30 Tagen untersucht, die als das Signal planetarer Wellen gelten. Im Zeitraum 1980-2005 werden deutliche Schwankungen von Jahr zu Jahr als auch langfristige Trends gefunden. Einer Zunahme der zonalen Komponente der Schwankungen seit 1990 steht eine Abnahme der meridionalen Komponente gegenüber. Diese Änderung erfolgt in rascher Form, so dass sich die Änderung der Zirkulation im Mesopausenbereich als klimatische Verschiebung, und weniger als Trend darstellt. Das Verhalten der Dynamik im Mesopausenbereich korrespondiert mit möglichen Änderungen klimatischer Parameter in anderen Schichten der Atmosphäre und weist auf eine Kopplung atmosphärischer Schichten untereinander hin
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Simmons, Shelton O'Brien. "A study of the mesosphere-lower thermosphere noctilucent cloud observations and rocket borne density measurements /." Connect to this title online, 2009. http://etd.lib.clemson.edu/documents/1263397391/.
Texte intégral