Dissertations / Theses on the topic 'Water vapour'
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1
Munro, Rosemary. "Middle atmosphere water vapour." Thesis, University of Oxford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293409.
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Alyanak, Didem Balköse Devrim. "Water vapour permeable edible membranes/." [s.l.]: [s.n.], 2005. http://library.iyte.edu.tr/tezler/master/biyoteknoloji/T000420.pdf.
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Calanca, Pierluigi Stefano. "The atmospheric water vapour budget over Greenland /." Zürich, 1993. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10243.
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Kennett, Elizabeth Jane. "Lifetime and variability of atmospheric water vapour." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425367.
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Goss-Custard, Matthew. "Measurements of atmospheric water vapour by ISAMS." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386586.
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Hubbard, Lisa C. M. "Atmospheric water vapour effects on GPS measurements." Thesis, University of Nottingham, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283462.
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Baker, Helen C. "GPS water vapour estimation for meteorological applications." Thesis, University of Nottingham, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263417.
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Chinnaswamy, Arulmani. "Water vapour and sea surface temperature retrievals." Thesis, University of Reading, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270328.
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Duan, Zhouyang. "Water vapour permeability of bio-based polymers." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/13609.
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This project investigates the moisture barrier properties of bio-based polymers and ways of improving them. The first section addresses the effect of crystallinity on the water permeability of poly(lactic acid) (PLA). The second section investigates PLA/talc composites and PLA/ montmorillonite nanocomposites. The third section is focused on a new polymer, polybutylene succinate (PBS), and its nanocomposites with montmorillonite. In the first section, the water vapour transmission rates (WVTR) through samples of polylactic acid of different crystallinities have been measured. Three different grades of commercial PLA were used with different ratios of L-lactide and D-lactide to give a range of crystallinities from 0 to 50%. Sheets of PLA were prepared by melt compounding followed by compression moulding and annealing at different temperatures and for different times to give the range of crystallinities required. Crystallinity was measured by differential scanning calorimetry (DSC) and the morphology of the samples was observed under crossed polars in a transmitted light microscope. Water vapour transmission rates through the films were measured at 38°C and at a relative humidity of 90%. It was found that the measured values of WVTR decreased linearly with increasing crystallinity of the PLA from 0 to 50%. The results are discussed in terms of the effect of crystallinity on solubility and shown to fit the tortuous path model. The model was also successfully used to explain published data on water permeability of polyethylene terephthalate. In the second section, a series of PLA/talc composites and PLA/ montmorillonite nanocomposites were prepared by melt compounding followed by compression moulding. The morphologies of the composites were investigated using transmission electron microscopy (TEM) and wide-angle X-ray diffraction (WAXD) and it was found that the fillers were well dispersed in the polymer matrix. The average aspect ratio of the compounded talc was found to be 8, and that of the nanoclay was found to be 50. Water vapour transmission rates (WVTR) through the films were measured at 38°C and at a relative humidity of 90%. It was found that the measured values of WVTR decreased with increasing filler content and the results gave good agreement with predictions from the Nielsen tortuous path model. In the third section, PBS/ montmorillonite nanocomposites were prepared by melt compounding followed by compression moulding. The melting and crystallisation behaviour of the pure PBS samples were investigated using differential scanning calorimetry (DSC) and cross polarised optical microscopy. A slight decrease of the degree of crystallinity was found in PBS containing 5% nanoclay. The morphology of the composites was investigated using transmission electron microscopy (TEM) and wide-angle X-ray diffraction (WAXD) and it was confirmed that that composite structures were intercalated. Water vapour transmission rates (WVTR) through the PBS sheets were measured using a MOCON Permatran-W®398. The measured values of WVTR decreased with increasing nanoclay content. However, the experimental values were all higher than the values predicted by the Nielsen tortuosity model. This result shows that in the case of PBS, which is a highly crystalline polymer, the nanoclay is not as well dispersed and is not as effective in reducing water vapour permeability as in the case of PLA.
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Wiedner, Martina Corinna. "Atmospheric water vapour and astronomical millimetre interferometry." Thesis, University of Cambridge, 1998. http://www.mma.nrao.edu/workinggroups/cal%5Fimaging/183GHz.html.
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Jalaludin, Zaihan. "The water vapour sorption behaviour of wood." Thesis, Edinburgh Napier University, 2012. http://researchrepository.napier.ac.uk/Output/4905.
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The water vapour sorption properties of several commercial tropical hardwoods and temperate softwood species as well as thermally modified wood and acetylated wood has been studied. A dynamic vapour sorption apparatus was used for this investigation to give data on the sorption isotherms under equilibrium conditions as well as sorption kinetic behaviour. Small differences in the sorption isotherms were found between the wood species, but modification resulted in substantial changes to the sorption isotherms. The sorption isotherms were analysed using the Hailwood-Horrobin model. Sorption kinetics behaviour was found to be accurately described using the parallel exponential kinetics (PEK) model. This model has only recently been applied to wood and this work represents a much more comprehensive study of the applicability of the model. Until now the favoured approach has been based upon Fickian models. The conventional interpretation of the PEK model relies upon the idea of different types of sorption sites, but his work has shown (partly based upon Hailwood-Horrobin analyses of the isotherms) that this interpretation is not applicable. Instead, an interpretation based upon relaxation limited kinetics has been adopted. These ideas are commonly employed in the polymer science literature, but have hardly been used in wood science. The model employed was that involving two Kelvin-Voigt elements in series, from which cell wall moduli and viscosities have been determined. The values of the moduli appear sensible, but the model is only tentative at this stage. The kinetic data has also been used to determine activation energies, entropies and Gibbs free energy of sorption. This is the first time that the entropy and Gibbs free energy of sorption have been studied. The purpose of this work was to understand the phenomenon of sorption hysteresis and in particular to examine if there was a link between sorption hysteresis and sorption kinetics.
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Crombie, Stephanie. "Carbon and water vapour exchange in a temperate fresh water marsh." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114374.
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The ability of wetlands to sequester carbon has given them a considerable amount of attention, especially in light of global climate change. To date, many wetland studies have focused on peatlands, however very few studies have been conducted on marshes. This study used the eddy covariance (EC) technique to measure net ecosystem carbon exchange (NEE) and energy exchange at a temperate freshwater cattail marsh near Ottawa, Canada. The objectives of the study were to use a four year dataset to determine the environmental controls on the variability of carbon and water vapour exchange. The annual cumulative NEE was on average -246 ± 31 gCm-2yr-1 ranging from -216 to -260 gCm-2yr-1. The variability in accumulation between years was a result of the timing of spring and fall transitions in the carbon uptake and the length of the growing seasons, each of which were determined by prevailing weather conditions. Evaluation of the interannual variability indicated that the marsh may be sensitive to carbon (C) losses through enhanced respiration under warmer autumn periods. Maximum daily average values of evapotranspiration (ET) reached 10.75, 9.07, 11.70 and 8.36 mm day-1 in 2005, 2006, 2007 and 2008, respectively. Bowen ratio values varied seasonally with values well below unity during the growing season (May to October) illustrating the dominance of latent heat. Evaluation of the evaporative fraction and Priestley-Taylor α indicated the seasonal importance of ET and mid-season high values of the decoupling coefficient (Ω) indicated that the marsh ET is radiatively driven owing its smooth aerodynamic surface and abundance of water. Overall, the marsh ecosystem was a large annual sink for CO2 as compared to other wetland ecosystems and ET rates were highly dependent on radiative input.La capacité des milieux humides à séquestrer du carbone a beaucoup attiré l'attention, notamment dans le contexte des changements climatiques. À ce jour, bien que plusieurs études aient été menées sur les tourbières, très peu portent sur les marais. Cette étude a utilisé la technique de covariance des turbulences afin de mesurer l'échange écosystémique net (EEN) de CO2 et l'échange d'énergie d'un marécage de quenouilles de l'est de l'Ontario, Canada. Les objectifs de cette étude étaient d'utiliser un ensemble de données de quatre ans afin de déterminer les contrôles environnementaux sur la variabilité des échanges de carbone et de vapeur d'eau. Le EEN annuel cumulé était en moyenne de -246 ± 26,8 gCm-2a-1 allant de -216 à -260 gCm-2a-1. La variabilité de l'accumulation entre les années était le résultat de la synchronisation du printemps et de l'automne au niveau de l'absorption du carbone et de la longueur des saisons de croissance, chacune ayant été déterminée par les conditions météorologiques qui prévalaient. L'étude de la variabilité interannuelle a indiqué que le marécage pourrait être sensible aux pertes de C causées par une augmentation de la respiration au cours de périodes plus chaudes d'automne. Les valeurs moyennes quotidiennes maximales d'évapotranspiration (ET) ont atteint 10,75, 9,07, 11,70 et 8,36 mm jour-1 en 2005, 2006, 2007 et 2008 respectivement. Les valeurs du rapport de Bowen variaient selon la saison, avec des valeurs bien en dessous de l'unité pendant la saison de croissance (mai à octobre), illustrant la dominance de la chaleur latente. Une évaluation de la fraction d'évaporation et du facteur α de Priestley-Taylor indiquaient l'importance saisonnière de l'ET et les valeurs élevées de mi-saison du facteur de découplage (Ω) indiquaient que l'ET du marais est dominé par les radiations en raison de sa surface aérodynamique lisse et de l'abondance d'eau. Dans l'ensemble, l'écosystème du marais était un grand puits de carbone annuel par rapport aux écosystèmes de tourbière et les taux d'ET étaient fortement dépendants de l'apport radiatif.
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Huizing, Ryan Nicholas. "Electrospun nanofibrous membranes for water vapour transport applications." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/61321.
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The full abstract for this thesis is available in the body of the thesis, and will be available when the embargo expires.Applied Science, Faculty of
Materials Engineering, Department of
Graduate
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Diedrich, Hannes [Verfasser]. "Observation of Total Column Water Vapour / Hannes Diedrich." Berlin : Freie Universität Berlin, 2016. http://d-nb.info/1109790406/34.
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Patmore, Nicola Ann. "Water vapour transport and mixing in the tropopause." Thesis, Imperial College London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432458.
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Ea, J.-Y. "Water vapour transfer in breathable fabrics for clothing." Thesis, University of Leeds, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.480540.
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Lossow, Stefan. "Observations of water vapour in the middle atmosphere." Doctoral thesis, Stockholm : Department of Meteorology, Stockholm University, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-8167.
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Hauschildt, Heike [Verfasser]. "Atmospheric liquid water and water vapour under all-sky conditions / Heike Hauschildt." Kiel : Universitätsbibliothek Kiel, 2008. http://d-nb.info/1019766905/34.
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Topçuoğlu, Özge Alsoy Altınkaya Sacide. "Sorption and transport of water vapour in Acrylic Paints/." [s.l.]: [s.n.], 2004. http://library.iyte.edu.tr/tezler/master/kimyamuh/T000498.pdf.
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Eichinger, Roland. "Investigation of stratospheric water vapour by means of the simulation of water isotopologues." Diss., Ludwig-Maximilians-Universität München, 2014. http://nbn-resolving.de/urn:nbn:de:bvb:19-172359.
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This modelling study aims to gain an improved understanding of the processes that determine the water vapour budget in the stratosphere by means of the investigation of water isotope ratios. At first, a separate hydrological cycle has been introduced into the chemistry-climate model EMAC, including the water isotopologues HDO and H218O and their physical fractionation processes. Additionally, an explicit computation of the contribution of methane oxidation to HDO has been incorporated. EMAC simulates explicit stratospheric dynamics and a highly resolved tropical tropopause layer. These model expansions, now allow detailed analyses of water vapour and its isotope ratio with respect to deuterium (deltaD(H2O)), throughout the stratosphere and in the transition region to the troposphere.
In order to assure the correct representation of the water isotopologues in the model's hydrological cycle, the expanded system has been evaluated in several steps. The physical fractionation effects have been evaluated by comparison of the simulated isotopic composition of precipitation with measurements from a ground-based network (GNIP) and with the results from an isotopologue-enabled ECHAM5 general circulation model version. The model's representation of the chemical HDO precursor CH3D in the stratosphere has been confirmed by a comparison with chemical transport models (CHEM1D, CHEM2D) and measurements from radiosonde
flights. Finally, the simulated HDO and deltaD(H2O) have been evaluated in the stratosphere, with respect to retrievals from three different satellite instruments (MIPAS, ACE-FTS, SMR).
Discrepancies in stratospheric deltaD(H2O) between two of the three satellite retrievals can now partly be explained. The simulated seasonal cycle of tropical deltaD(H2O) in the stratosphere exhibits a weak tape recorder signal, which fades out at altitudes around 25 km. This result ranges between the pronounced tape recorder signal in the MIPAS observations and the missing upward propagation of the seasonal variations in the ACE-FTS retrieval. Revisions of different insufficencies in the respective satellite measurements, however, are expected to alter both observational datasets towards the results of the EMAC model.
Extensive analyses of the water isotope ratios have revealed the driving mechanisms of the stratospheric deltaD(H2O) tape recorder signal in the EMAC simulation. A sensitivity study without the impact of methane oxidation on deltaD(H2O) demonstrates the damping effect of this chemical process on the tape recorder signal. An investigation of the origin of the enhanced deltaD(H2O) in the lower stratosphere during boreal summer, shows isotopically enriched water vapour, crossing the tropopause over the subtropical Western Pacic. A correlation analysis confirms this link, and thus the Asian Summer Monsoon could be identified to be the major contributing process for the stratospheric deltaD(H2O) tape recorder. This finding contradicts an analysis of ACE-FTS satellite data, which assigns the lower stratospheric deltaD(H2O) increase during boreal summer to the North American Monsoon. A possible explanation for this discrepancy has been found to be an underrepresentation of convective ice overshooting in the applied convection scheme.Diese Modellstudie hat ein besseres Verständnis jener Prozesse zum Ziel, die das Wasserdampfbudget in der Stratosphäre bestimmen und stützt sich auf die Untersuchung des Isotopenverhältnisses von Wasser. Zunächst wurde ein eigenständiger hydrologischer Zyklus in das Chemie-Klimamodell EMAC eingebaut, welcher die Wasserisotopologe HDO und H218O sowie deren physikalische Fraktionierungsprozesse enthält. Zusätzlich wurde eine explizite Berechnung des Beitrages der Methanoxidation zu HDO eingefügt. EMAC simuliert eine hochaufgelöste tropische Tropopausenschicht sowie explizite Stratosphärendynamik. Mit diesen Modellerweiterungen ist es nun möglich, genaue Analysen von Wasserdampf und dessen Isotopenverhältnis im Bezug auf Deuterium (deltaD(H2O)) in der gesamten Stratosphäre, sowie im Übergangsbereich zur Troposphäre durchzuführen. Um die korrekte Darstellung der Wasserisotopologe im hydrologischen Zyklus des Modells zu gewährleisten, wurde das erweiterte System in mehreren Schritten evaluiert. Die physikalischen Fraktionierungseffekte wurden in einem Vergleich der simulierten Isotopenverhältnisse im Niederschlag mit Messungen eines Netzwerkes an Bodenstationen (GNIP) und mit Ergebnissen einer, mit Wasserisotopologen ausgestatteten, ECHAM5 Modellversion evaluiert. Die Güte des simulierten chemischen HDO-Vorläufers CH3D in der Stratosphäre des Modells wurde durch einen Vergleich der Ergebnisse mit chemischen Transportmodellen (CHEM1D, CHEM2D) und Messungen von Radiosondenaufstiegen überprüft. Abschließend wurde simuliertes HDO und deltaD(H2O) anhand von Messungen drei verschiedener Satelliteninstrumente (MIPAS, ACE-FTS, SMR) evaluiert. Abweichungen im deltaD(H2O) zwischen zwei der drei satellitengestützten Beobachtungen können nun teilweise erklärt werden. Der simulierte Jahresgang von tropischem deltaD(H2O) in der Stratosphäre weist ein schwaches 'tape recorder' Signal auf, welches sich in Höhen um 25 km auflöst. Dieses Ergebnis ist zwischen das ausgeprägte 'tape recorder' Signal in MIPAS- Beobachtungen und die nicht erkennbare vertikale Ausbreitung des Jahresgangs in ACE-FTS-Messungen einzuordnen. Die Beseitigung unterschiedlicher Mängel in den jeweiligen Satellitenmessungen lässt jedoch eine Veränderung beider Beobachtungsdatensätze in Richtung der Ergebnisse des EMAC Modells erwarten. Eingehende Analysen der Wasserisotopenverhältnisse in der EMAC Simulation haben die für den stratosphärischen deltaD(H2O)-'tape recorder' verantwortlichen Prozesse aufgezeigt. Eine Sensitivitätsstudie ohne Einfluss der Methanoxidation auf deltaD(H2O) veranschaulicht den dämpfenden Einfluss dieses chemischen Prozesses auf das 'tape recorder' Signal. Eine Untersuchung des Ursprungs des erhöhten deltaD(H2O) in der unteren Stratosphäre im Nordsommer weist isotopisch angereicherten Wasserdampf nach, welcher die Tropopause über dem subtropischen Westpazifik durchquert. Eine Korrelationsanalyse bestätigt diese Verbindung und kennzeichnet damit den Asiatischen Sommermonsun als den wesentlichen beitragenden Faktor zum stratosphärischen deltaD(H2O)-'tape recorder'. Dieses Ergebnis steht im Gegensatz zu einer Auswertung von ACE-FTS-Satellitendaten, welche den deltaD(H2O) Anstieg in der unteren Stratosphäre im Nordsommer dem Nordamerikanischen Monsun zuweist. Als mögliche Erklärung für diesen Widerspruch konnte das, in dem verwendeten Konvektionsschema unzureichend auftretende, konvektive Überschießen von Wolkeneis ausgemacht werden.
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Daya, Zeinab A. "The thermodynamics of water vapour dissolution in tundish fluxes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ28871.pdf.
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Sodemann, Harald. "Tropospheric transport of water vapour Lagrangian and Eulerian perspectives." Berlin Logos-Verl, 2006. http://deposit.d-nb.de/cgi-bin/dokserv?id=2888383&prov=M&dok_var=1&dok_ext=htm.
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Fischer, Lucas. "Statistical characterisation of water vapour variability in the troposphere." Diss., Ludwig-Maximilians-Universität München, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-162089.
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Tropospheric water vapour plays an important role in thermodynamic and radiative processes which have an immediate impact on the weather and climate system.
However, the processes that determine the distribution of water vapour remain poorly understood.
The complexity arises out of a range of source and sink processes from convective clouds on the kilometre scale to cloud systems associated with motions on scales of a thousand or more kilometres, as well as advection of water vapour as a passive tracer outside of clouds.
While large-scale advection of water vapour is well represented in general circulation models, the simulation of small-scale moist processes that are of central importance to the representation of clouds are heavily dependent on parameterisations.
However, observations as well as processes that determine the distribution of the water vapour field are insufficiently explored, leading to constrained parameterisations and therefore contributing significantly to the uncertainty of numerical weather and climate predictions.
Hence, a more accurate description of the inhomogeneous water vapour field based on high-resolution observations is required.
This thesis investigates a comprehensive data set of two-dimensional airborne water vapour observations in the free troposphere collected by a Differential Absorption Lidar (DIAL) in order to gain a height-resolved statistical characterisation of the inhomogeneous water vapour field.
Structure functions, i.e., statistical moments up to the fifth order of absolute increments over a range of scales, are investigated and power-law behaviour or scale dependence is identified over horizontal distances from about 5~km to 100~km. The slope of the power-law fit, the so-called scaling exponent, is found to take different values, depending on whether or not the observations were taken in an air mass where convective clouds were present. These results are consistent with a non-convective regime that is dominated by large-scale advective processes, leading to monofractal scaling, but strong localised input of small-scale variability by convective circulations leading to intermittent fields.
Further, the observed power-law statistics are used to evaluate the high-resolution numerical weather prediction model COSMO-DE of the German weather service with regard to the small-scale water vapour variability. The results of the scaling exponent analysis of cloud-free and partly cloudy scenes suggest, that the small-scale variance is modeled quite well in comparison with the lidar observations. By using the advantage of the model simulation where data is not limited to a specific flight path, the influence of sampling limitation is estimated and is found to be not significant. Further, the simulation provides humidity data in and beneath clouds which allows for an estimation of the uncertainty of data gaps in the lidar observations due to optically thick clouds. The error is identified to be in a range of only few percents.
This thesis demonstrates that airborne DIAL observations are useful to build up a height-resolved statistical characterisation of tropospheric water vapour variability that allows to distinguish physical mechansims that are responsible for the water vapour distribution, to get new insights into stochastic parameterisations and further to use the structure function method as a suitable reality check of the numerical weather model COSMO-DE.
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Hamm, Torolf Klaus. "The response of a porous stone to water vapour." Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269685.
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Comer, Ruth Elizabeth. "Understanding the diurnal cycle in clouds and water vapour." Thesis, University of Reading, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.446198.
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Koukouli, Mary Elizabeth. "Remote sensing of water vapour in Venus' middle atmosphere." Thesis, University of Oxford, 2002. http://ora.ox.ac.uk/objects/uuid:60216894-5d24-431a-99f0-cc8b0709cb30.
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The Pioneer Venus Orbiter Infrared Radiometer and Venera 15 Fourier Transform Spectrometer observations of thermal emission from Venus' middle atmosphere between 10°S and 50°N were used to determine global maps of temperature, cloud optical depth and water vapour abundance. The spectral regions observed include the strong 15 μtm carbon dioxide band and the 45 μm fundamental rotational water band. The main aim of this thesis is to reconcile the water vapour abundance results from these two sets of observations reported in previous studies. New radiative transfer and retrieval models have been developed for this purpose based on new correlated-k absorption tables calculated with up-to-date spectral line data. The H2SO4 cloud opacity and scattering properties have been recalculated from new refractive index data using Mie theory. For the first time these two sets of observations have been analysed using the same retrieval tools. From the Pioneer Venus Orbiter Infrared Radiometer observations we report a high abundance of water vapour in the early afternoon at the equatorial cloud-top region and a strong day-night variability in the cloud-top pressure. From the Venera 15 Fourier Transform Spectrometer observations we report medium local variability in water vapour abundance, with highest values in the near-equatorial region and slight decrease towards the polar region. It is found that serious constraints are placed on the validation of the retrievals by the lack of adequately accurate H2SO4 optical properties data in the shorter wavelengths and by the poor vertical resolution when sensing the complex but interesting cloud region which prohibits its rigorous modelling. The proposed European Space Agency Venus Express mission will carry a number of high resolution infrared and UV instruments that will shed new light to the interesting question of water vapour abundance in Venus' middle atmosphere.
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Dethof, Antje. "Quasi-horizontal water vapour transport across the dynamical tropopause." Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301955.
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Zhang, Rui. "Modelling carbon dioxide and water vapour over European forests." Thesis, University of Edinburgh, 2007. http://hdl.handle.net/1842/10672.
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We tested several hypotheses which all link the carbon cycling in European forests using the Soil-Plant-Atmosphere model (SPA) and eddy covariance measurements from the CARBOEUROPE project. Firstly we run the model against flux data and obtained the optimised set of parameters for ten flux sites at a variety of climatic conditions. The inter-site model parameters are investigated to test whether the variations in parameters display a pattern which can be used in up-scaling of model application. It was found that maximum carbonylation rate (Vcmax) displays a simple linear relationship with latitude (R2 = 0.72) and the ratio of autotrophic respiration to GPP remains at a constant (0.47). Furthermore we applied a Bayesian calibration method, which quantifies both flux measurement error and parameter priori distribution, to the same ten flux sites to tackle the uncertainty of model outputs. It was found that given amount of data and associated errors, model parameters and the confidence intervals that are related to plant functional type (PFT) can be identified. The third hypothesis we tested in the thesis is that carbon uptake by plant is enhanced under diffuse radiation. We compared the light use efficiency (LUE) under both direct and diffuse regime for eight contrasting ecosystems using both flux data and modelled outputs. Our results show that diffuse radiation results in a higher LUE for both forests and grasslands and response of forests to diffuse radiation is even higher. The model produced strikingly similar results. Finally we applied the model to a specific flux site experiencing drought to test the hypothesis that soil moisture and precipitation may influence the carbon uptake of forests and further have an impact on the carbon cycling.
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Johansson, Erik. "Simulations of water clustering in vapour, hydrocarbons and polymers." Doctoral thesis, Högskolan i Borås, Institutionen Ingenjörshögskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-3436.
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It is commonly known that water plays a crucial role in many natural and industrial processes. One of these processes is the formation of water trees, and the subsequent breakdown of polyethylene used for high voltage cable insulation purposes. It has been shown that the mechanism for water molecules diffusing through amorphous polyethylene includes the formation of small water clusters. Gibbs Ensemble Monte Carlo molecular simulations has been performed to study the clustering of vapour phase water under vapour - liquid equilibrium conditions at temperatures ranging from 300 K to 600 K. The increase in vapour density with increasing temperature leads to a radical increase in the fraction of molecules belonging to clusters with two or more water molecules. It is also seen that the size of the clusters increases with temperature. The topologies of the smaller clusters, up to pentamers, have also been studied. A structural transition is observed from a large percentage with cyclic topology, which is the minimum energy configuration, at lower temperatures to predominantly linear clusters, favoured by entropic effects, at higher temperatures. Similar water properties have been obseved in simulations where the vapour phase has been replaced with a hydrocarbon rich phase ( n-alkanes and polyethylene ). Application of an external electric field to the polymer system reduces the water solubility and affects the water structure. A dramatic increase in water solubility in the hydrocarbon phase is observed when two oppositely charged ions are introduced in the hydrocarbon. The structure of the water have changed from several small clusters to a single large cluster with a rod-like shape. The cluster is extremely stable during the simulation. Application of an external electric field may enhance or reduce the effect of the ions depending on the direction of the field. Based on these observations is an alternative mechanism for water tree propagation proposed.
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Trent, Timothy James. "Climate and variability of water vapour in the troposphere." Thesis, University of Leicester, 2015. http://hdl.handle.net/2381/32243.
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Atmospheric water vapour is an important (natural) greenhouse gas, infuencing both directly and indirectly the global radiative balance of the Earth as well as heat and moisture fluxes at the surface. Since water vapour concentrations may change as a result of surface warming and other environmental/meteorological factors, there is a need to understand the long-term behaviour. Changes are small, so it is critical to use high quality data with well-defined uncertainties and biases, particularly for climate research. Hyper-spectral infrared (IR) sounders such as the Infrared Atmospheric Sounding Interferometer (IASI) and the Atmospheric Infrared Sounder (AIRS) allow for higher vertical resolution profile measurements of water vapour to be obtained compared to their predecessors. First results of global comparisons of AIRS profiles show that for tropospheric layers between 925-374 hPa biases are within +-10% and a significant dry bias of 20% in regions of the upper troposphere, consistent with recent comparisons to reanalysis. A consistent approach to the retrieval of temperature and water vapour profiles from all hyper-spectral IR sounders is outlined and an initial set of retrievals from IASI at global climate sites is performed. Results from the University of Leicester Water Vapour Processor (UoL-WVP) show errors of ≈1 K and Atmospheric water vapour is an important (natural) greenhouse gas, infuencing both directly and indirectly the global radiative balance of the Earth as well as heat and moisture fluxes at the surface. Since water vapour concentrations may change as a result of surface warming and other environmental/meteorological factors, there is a need to understand the long-term behaviour. Changes are small, so it is critical to use high quality data with well-defined uncertainties and biases, particularly for climate research. Hyper-spectral infrared (IR) sounders such as the Infrared Atmospheric Sounding Interferometer (IASI) and the Atmospheric Infrared Sounder (AIRS) allow for higher vertical resolution profile measurements of water vapour to be obtained compared to their predecessors. First results of global comparisons of AIRS profiles show that for tropospheric layers between 925-374 hPa biases are within +-10% and a significant dry bias of 20% in regions of the upper troposphere, consistent with recent comparisons to reanalysis. A consistent approach to the retrieval of temperature and water vapour profiles from all hyper-spectral IR sounders is outlined and an initial set of retrievals from IASI at global climate sites is performed. Results from the University of Leicester Water Vapour Processor (UoL-WVP) show errors of ≈1 K and ≤20% within the troposphere for temperature and humidity respectfully. The significance of surface characterisation at a sub-pixel level is also demonstrated. Retrievals from IASI at selected climate sites for 2012 are inter-compared in a three-way analysis with high resolution radiosonde profiles and AIRS data. Results show that the mean standard deviation of observational error for IASI is 2.2% while AIRS is 3.6%. This thesis work represents a step forward in the use of AIRS and IASI data for climate research. However, proven long-term stability is needed for the water vapour data question to be answered. and humidity respectfully. The significance of surface characterisation at a sub-pixel level is also demonstrated. Retrievals from IASI at selected climate sites for 2012 are inter-compared in a three-way analysis with high resolution radiosonde profiles and AIRS data. Results show that the mean standard deviation of observational error for IASI is 2.2% while AIRS is 3.6%. This thesis work represents a step forward in the use of AIRS and IASI data for climate research. However, proven long-term stability is needed for the water vapour data question to be answered.
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Combrink, Adriaan Zacharias Albertus. "Sensing atmospheric water vapour using the global positioning system." Doctoral thesis, University of Cape Town, 2006. http://hdl.handle.net/11427/14811.
Full textAbstract:
Includes bibliographical references .Atmospheric water vapour measurements are of importance to meteorologists, radio astronomers and geodesists. Precipitable water vapour (PWV) is a greenhouse gas to be reckoned with in numerical weather models and climate change studies, it is a nuisance in centimetre-wavelength radio astronomy and introduces range errors in space geodetic techniques. The propagation time of electromagnetic waves is the principal observable in the Global Positioning System (GPS). Accurate estimates of the delays experienced by the radio signals travelling from the satellites to ground-based receivers are made during the post-processing of GPS observations. In combination with meteorological observations made at the receiver, the estimated delays can be used to determine the amount of integrated precipitable water vapour along the signal path. In this thesis an overview of the basic GPS principles and components is provided, as well as a derivation, from first physical principles, of the mechanisms contributing to the delay experienced by a radio signal traversing the ionosphere and troposphere. Implementing this theoretical background, PWV and tropospheric delays are estimated and compared to measurements made by other techniques, namely radiosondes, water vapour radiometry and very long baseline interferometry (VLBI). A high degree of correlation is observed in all instances of inter-technique comparison. The usefulness of GPS-derived slant delays is demonstrated by their ability to reduce VLBI inter-station baseline repeatabilities when they are included in the VLBI analysis. However, this contributed to a higher mean formal baseline error. Furthermore, it shown that GPS-derived slant delay accuracies, when compared to radiometry, can be improved through the stacking of GPS processing residuals to make corrections for the effects of multi path and antenna phase centre variations. A modified residual stacking (MRS) method is proposed, in which data weighting is based on a measured autocorrelation function; however, in most instances the more complex MRS failed to significantly improve on the corrections made by normal residual stacking. GPS-derived PWV time-series from thirty South African stations for a four-year period are presented. A four-parameter model was fitted to the time-series to correct for seasonal effects and detect linear trends. It is shown that an autoregressive moving average (ARMA) model is required to estimate realistic trend uncertainties, rather than the white-noise model implicit in standard least-squares analyses. Furthermore, significant trends in PWV were observed in South Africa with the central parts showing a decrease in PWV during the study period, while an increase is observed over the southwest and northeast. These trends coincide with a temperature increase observed over the whole of South Africa for the study period. A hypothesis is presented to explain the different trends, based on the different sources of PWV in different climate areas. Lastly, vertical earth tide displacements (VETD) measured by gravimetry are compared to the modelled VETD applied during GPS processing. It is shown that rnismodelled VETD can contribute significant errors to GPS-derived PWV. A number of methods to mitigate this error are proposed and compared to each other, including a novel technique to accurately measure VETD by GPS.
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Tanaka, Mizuho. "Analysis of the spectra of isotopically substituted water vapour." Thesis, University College London (University of London), 2005. http://discovery.ucl.ac.uk/1446544/.
Full textAbstract:
The spectrum of water vapour is widely studied due to its significance in many areas of science. Isotopically substituted water vapour such as H 217O and H218O are known to contribute significantly to the absorption of solar radiation in the Earth's atmosphere, yet they have been less extensively studied. Recent advances in the variational nuclear motion calculations, high quality potential energy surfaces (PES) and dipole moment surfaces (DMS) allow us to accurately calculate the energy levels and spectra of water vapour. Using the DVR3D program suite developed at UCL, the energy levels of D2O have been calculated in order to analyse the spectrum by the D2O laser. The calculated band origins of D2O is given in this thesis. New linelists for H2 17O and H218O are also generated using the DVR program suite. Using these linelists, several experimental spectra of isotopically substituted water vapour have been studied. We analysed the H 217O and H218O spectra measured by Fourier transform spectrometer at Kitt Peak National Solar Observatory (AZ, USA). Both spectra lie m 3+ and 4 polyad region where currently no data is publicly available. We also analysed the the H217O and H218O spectra in 5? polyad region recorded by cavity ring-down spectroscopy at the Vrije Universiteit (Amsterdam, the Netherlands). The wavenumber region analysed in this work is the highest to date for both water isotopologues. The results of analyses are presented in this thesis.
33
Rodger, Andrew P. "Atmospheric water vapour determination from remotely sensed hyperspectral data." Thesis, Curtin University, 2002. http://hdl.handle.net/20.500.11937/701.
Full textAbstract:
The accurate estimation of atmospheric water vapour and the subsequent derivation of surface spectral reflectance from hyperspectral VNIR-SWIR remotely sensed data is important for many applications. A number of algorithms have been developed for estimating water vapour content from remotely sensed hyperspectral data that do not require in-situ measurements. Two algorithms, the Continuum Interpolated Band Ratio (CIBR) and the Atmospheric Precorrected Differential Absorption (APDA) have proven to be highly effective at estimating atmospheric water vapour. Although highly successful, the two methods still exhibit unwanted or spurious results when challenging conditions are encountered. Such conditions include the estimation of atmospheric water vapour over dark targets, when uncorrected atmospheric aerosols are present and over surfaces with complex spectral signatures.A differential absorption method called the Transmittance Slope Ratio (TSR) has been developed that negates these problems. The TSR method is comprised of a weighted mean radiance that is defined between two atmospheric water absorption features which is divided by a reference channel radiance to produce a measurable ratio value. This, is turn, may be related to a reference curve, such that, the TSR value may be expressed as an atmospheric water vapour content. To test the TSR method over real terrains, AVIRIS and HyMap measured hyperspectral radiometric data were used. Three test sites were used in total with each site allowing different aspects of the water vapour estimation to be critically examined. The sites are, Jasper Ridge and Moffett Field in California and Brukunga in South Australia.The TSR method is found to significantly improve estimated atmospheric water vapour over dark targets (with less than 3.5 % error for reflectances as low as 0.5 %), improvement over nonlinear surfaces, and finally, improvement in water vapour estimation when atmospheric aerosol conditions are not well known. In the final case the TSR method is found to estimate atmospheric water vapour with an error of less than 2 % when a 5 km visibility is assumed to be 25 km. The final result is at least an order of magnitude better than the CIBR and APDA methods.
34
Rodger, Andrew P. "Atmospheric water vapour determination from remotely sensed hyperspectral data." Curtin University of Technology, School of Applied Science, 2002. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=12544.
Full textAbstract:
The accurate estimation of atmospheric water vapour and the subsequent derivation of surface spectral reflectance from hyperspectral VNIR-SWIR remotely sensed data is important for many applications. A number of algorithms have been developed for estimating water vapour content from remotely sensed hyperspectral data that do not require in-situ measurements. Two algorithms, the Continuum Interpolated Band Ratio (CIBR) and the Atmospheric Precorrected Differential Absorption (APDA) have proven to be highly effective at estimating atmospheric water vapour. Although highly successful, the two methods still exhibit unwanted or spurious results when challenging conditions are encountered. Such conditions include the estimation of atmospheric water vapour over dark targets, when uncorrected atmospheric aerosols are present and over surfaces with complex spectral signatures.A differential absorption method called the Transmittance Slope Ratio (TSR) has been developed that negates these problems. The TSR method is comprised of a weighted mean radiance that is defined between two atmospheric water absorption features which is divided by a reference channel radiance to produce a measurable ratio value. This, is turn, may be related to a reference curve, such that, the TSR value may be expressed as an atmospheric water vapour content. To test the TSR method over real terrains, AVIRIS and HyMap measured hyperspectral radiometric data were used. Three test sites were used in total with each site allowing different aspects of the water vapour estimation to be critically examined. The sites are, Jasper Ridge and Moffett Field in California and Brukunga in South Australia.The TSR method is found to significantly improve estimated atmospheric water vapour over dark targets (with less than 3.5 % error for reflectances as low as 0.5 %), improvement over nonlinear surfaces, and finally, ++improvement in water vapour estimation when atmospheric aerosol conditions are not well known. In the final case the TSR method is found to estimate atmospheric water vapour with an error of less than 2 % when a 5 km visibility is assumed to be 25 km. The final result is at least an order of magnitude better than the CIBR and APDA methods.
35
Bai, Zhengdong. "Near-Real-Time GPS Sensing of Atmospheric Water Vapour." Thesis, Queensland University of Technology, 2005. https://eprints.qut.edu.au/16059/1/Zhengdong_Bai_Thesis.pdf.
Full textAbstract:
An important goal in modern weather prediction is to improve short-term weather
forecasts, especially of severe weather and precipitation. However, the ability to
achieve this goal is hindered by the lack of timely and accurate observations of
atmospheric water vapour, which is one of the most poorly measured and least
understood constituents of the Earth's atmosphere due to its high temporal and spatial
variability. This situation is being addressed by the Global Positioning System (GPS)
technology. GPS radio signals are slowed and bent by changes in temperature,
pressure and water vapour in the atmosphere. Traditionally, the GPS signal
propagation delay is considered a nuisance parameter that is an impediment to
obtaining precise coordinates using GPS. Recent development in GPS precise
positioning and orbit determination has enabled the atmospheric parameters to be
determined to a high degree of accuracy on a routine basis, using continuous tracking
data from ground-based GPS receivers.
The aim of this research is to address several critical scientific challenges in
estimating the atmospheric water vapour content in near-real-time (NRT) in
Australia. Contributions are made to the field of GPS meteorology in the following
five areas:
First of all, research efforts were made to develop a technical platform for the
ground-based GPS meteorology studies and demonstration of GPS Precipitable
Water Vapour (PWV) estimation using observations from Australian Regional GPS
Networks (ARGN). Methods of estimation of water vapour from GPS and
radiosonde data have been developed and tested. GAMIT-based GPS data processing
strategies and compare analysis with radiosonde water vapour solutions from the
Australia Upper Air Network (AUAN) were undertaken, providing an effective
technical basis for further studies.
Secondly, the research has developed techniques to allow estimation of atmospheric
water vapour from GPS data and surface meteorological observations collected
around the GPS sites. Ideally a dedicated meteorological sensor is installed adjacent
to the GPS antenna. However, meteorological sensors are normally not installed at
most Australian GPS stations. Installing a new meteorological sensor at each GPS
station would involve additional cost at the level of one-third or half of the geodetic
GPS receiver cost. We have experimentally developed and demonstrated
interpolation methods for making use of hourly collected surface meteorological data
from the Australian Automatic Weather Station (AWS) network operated by the
Bureau of Meteorology (BOM) to estimate atmospheric water vapour.
Thirdly, the research has studied ocean tidal loading and its effects on GPS derived
precipitable water vapour estimates. The periodic motion of the Earth's surface due
to ocean loading is one of the largest periodic motions. However, very little work has
been done to quantify their effects on GPS-derived solutions at the GPS sites in the
Australian region surrounded by ocean waters. The research presents the theoretical
analysis and experimental results from the ARGN network, focusing on ocean
loading and its effects on GPS derived precipitable water vapour estimates.
The fourth important effort was the development of techniques for estimating highrate
Slant Water Vapour (SWV) values for future operational meteorological
applications in Australia, including addressing such issues as slant-path delay
recovery from post-fit double-difference residuals, and overcoming site multipath
effects. The experimental results have demonstrated the efficiency of the proposed
methods.
Finally, in order to address the meteorological applications with the existing and
anticipated GPS reference stations in the Australian region, and measure the
atmospheric water vapour content in near-real-time, the technical issues to
implement NRT GPS water vapour estimation were identified and discussed,
including the data requirements for meteorological and climate applications, NRT
data processing and quality control procedures for GPS orbits. The experimental
GPS PWV results from NRT and post data processing are compared and presented.
36
Bai, Zhengdong. "Near-Real-Time GPS Sensing of Atmospheric Water Vapour." Queensland University of Technology, 2005. http://eprints.qut.edu.au/16059/.
Full textAbstract:
An important goal in modern weather prediction is to improve short-term weather forecasts, especially of severe weather and precipitation. However, the ability to achieve this goal is hindered by the lack of timely and accurate observations of atmospheric water vapour, which is one of the most poorly measured and least understood constituents of the Earth's atmosphere due to its high temporal and spatial variability. This situation is being addressed by the Global Positioning System (GPS) technology. GPS radio signals are slowed and bent by changes in temperature, pressure and water vapour in the atmosphere. Traditionally, the GPS signal propagation delay is considered a nuisance parameter that is an impediment to obtaining precise coordinates using GPS. Recent development in GPS precise positioning and orbit determination has enabled the atmospheric parameters to be determined to a high degree of accuracy on a routine basis, using continuous tracking data from ground-based GPS receivers. The aim of this research is to address several critical scientific challenges in estimating the atmospheric water vapour content in near-real-time (NRT) in Australia. Contributions are made to the field of GPS meteorology in the following five areas: First of all, research efforts were made to develop a technical platform for the ground-based GPS meteorology studies and demonstration of GPS Precipitable Water Vapour (PWV) estimation using observations from Australian Regional GPS Networks (ARGN). Methods of estimation of water vapour from GPS and radiosonde data have been developed and tested. GAMIT-based GPS data processing strategies and compare analysis with radiosonde water vapour solutions from the Australia Upper Air Network (AUAN) were undertaken, providing an effective technical basis for further studies. Secondly, the research has developed techniques to allow estimation of atmospheric water vapour from GPS data and surface meteorological observations collected around the GPS sites. Ideally a dedicated meteorological sensor is installed adjacent to the GPS antenna. However, meteorological sensors are normally not installed at most Australian GPS stations. Installing a new meteorological sensor at each GPS station would involve additional cost at the level of one-third or half of the geodetic GPS receiver cost. We have experimentally developed and demonstrated interpolation methods for making use of hourly collected surface meteorological data from the Australian Automatic Weather Station (AWS) network operated by the Bureau of Meteorology (BOM) to estimate atmospheric water vapour. Thirdly, the research has studied ocean tidal loading and its effects on GPS derived precipitable water vapour estimates. The periodic motion of the Earth's surface due to ocean loading is one of the largest periodic motions. However, very little work has been done to quantify their effects on GPS-derived solutions at the GPS sites in the Australian region surrounded by ocean waters. The research presents the theoretical analysis and experimental results from the ARGN network, focusing on ocean loading and its effects on GPS derived precipitable water vapour estimates. The fourth important effort was the development of techniques for estimating highrate Slant Water Vapour (SWV) values for future operational meteorological applications in Australia, including addressing such issues as slant-path delay recovery from post-fit double-difference residuals, and overcoming site multipath effects. The experimental results have demonstrated the efficiency of the proposed methods. Finally, in order to address the meteorological applications with the existing and anticipated GPS reference stations in the Australian region, and measure the atmospheric water vapour content in near-real-time, the technical issues to implement NRT GPS water vapour estimation were identified and discussed, including the data requirements for meteorological and climate applications, NRT data processing and quality control procedures for GPS orbits. The experimental GPS PWV results from NRT and post data processing are compared and presented.
37
Querel, Richard Robert, and University of Lethbridge Faculty of Arts and Science. "Remote sensing of atmospheric water vapour above the Chilean Andes." Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Physics and Astronomy, 2010, 2010. http://hdl.handle.net/10133/2586.
Full textAbstract:
Water vapour is the principle source of opacity at infrared wavelengths in the Earth’s atmosphere.
In support of site testing for the European Extremely Large Telescope (E-ELT),
we have used La Silla and Paranal as calibration sites to verify satellite measurements of
precipitable water vapour (PWV). We reconstructed the PWV history over both sites by
analysing thousands of archived high-resolution echelle calibration spectra and compared
that to satellite estimates for the same period. Three PWV measurement campaigns were
conducted over both sites using several independent measurement techniques. Radiosondes
were launched to coincide with satellite measurements and provide a PWV reference
standard allowing intercomparison between the various instruments and methods. This
multi-faceted approach has resulted in a unique data set. Integral to this analysis is the
internal consistency provided by using a common atmospheric model.xvii, 206 leaves : ill. (some col.) ; 28 cm
38
Dodd, James Paul. "Diagnostics and models of the global atmospheric water." Thesis, University of Reading, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260662.
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Albert, Peter. "Remote sensing of atmospheric water vapour for numerical weather prediction." [S.l.] : [s.n.], 2005. http://www.diss.fu-berlin.de/2005/113/index.html.
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Smith, Claire Anne. "The radiative effects of observed trends in stratospheric water vapour." Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395646.
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Davis, G. R. "Remote sensing of atmospheric water vapour by pressure modulation radiometry." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233505.
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Burchell, Ian Robert. "Water vapour and temperature retrievals from the EURECA occultation radiometer." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337562.
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Reininger, Francis M. "A spatially modulated interferometer for mapping Martian water vapour sources." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365352.
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Fiadzomor, Phyllis Aku Yayra. "Trace detection of water vapour by cavity ring-down spectroscopy." Thesis, University of Bristol, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492638.
Full textAbstract:
A continuous wave cavity ring-down (CRD) spectrometer has been developed for the measurement of trace levels of water vapour by absorption spectroscopy at wavelengths m make cavity ring-down spectroscopy potentially more useful than current techniques for measurement of trace water in process gases and vacuum environments of semiconductor manufacture where water vapour contamination has a detrimental effect on the final product.
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Maycock, Amanda Claire. "The impact of changes in stratospheric water vapour on climate." Thesis, University of Reading, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.558720.
Full textAbstract:
. There is now overwhelming evidence that the stratosphere and troposphere behave as a two-way dy- namically coupled system, such that changes in temperature and wind in the stratosphere can influence the tropospheric circulation and vice versa. This has motivated interest in the role of the stratosphere in determining the climate response to forcing. Observations show that stratospheric water vapour (SWV) increased by ",30% between 1980 and 2000. Despite this, few studies have assessed the tropospheric dynamical response to SWV trends; this is the main aim of this thesis. The first part of the thesis focuses on modelling the radiative response to changes in SWV. It is shown that there are differences of up to ",70% in the magnitude of the temperature response to a given SWV perturbation between two different broad-band radiation codes. The physical basis for the structure of the purely radiative temperature response to an increase in SWV is then considered. The largest cooling occurs in the lower stratosphere and is enhanced in the extratropics compared to the tropics. The typically low concentration of SWV (a few ppmv) and the horizontal gradient in tropopause height are shown to be the dominant drivers of this structure. The second part of the thesis considers the response to SWV perturbations in global climate models (GCMs). An advanced GCM (H~dGAM I) is used to test the response to changes in SWV in the absence of changes in sea surface temperatures (SSTs). A uniform doubling in SWV results in a poleward shift in the rnidlatitude jets, a more positive annular mode index and an increase in the strength of the Brewer- Dobson circulation. In the more simplified Reading IGCM, the inclusion of the changes in SSTs causes a negative feedback, which reduces the amplitude of the tropospheric circulation response to a uniform SWV perturbation.
46
Salih, Hamid Hadi. "Process simulation of an engine driven vapour compression desalination plant." Thesis, University of Hertfordshire, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387146.
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Lei, Wenwen. "The physics of water leaks and water nanoflows." Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/13295.
Full textAbstract:
The encapsulation of devices sensitive to moisture is necessary to prolong lifetimes under adverse environmental conditions. Therefore, quantifying moisture flow is important in design and verification of the encapsulations. Gaseous flows have been studied after Knudsen’s paper appeared in 1909, with one important exception: water vapour. A recent unexpected finding from Holt et al. concerned ultra-fast water and air flows in carbon nanotubes. While Gruener and Huber did not obtain ultra-fast nitrogen flows in silicon nanotubes. This leaves us to concern main effective factors for flows in tubes. We use a theory of extended Navier-Stokes equations, having one equation for all flow regimes with an empirical parameter (Cha and McCoy theory), for predicting flow rates of nitrogen and water vapour through a 25 μm diameter silica glass cylindrical tube under isothermal condition. We measure nitrogen flow rates through microtubes across a wide range of Knudsen number (0.0048 ~ 12.4583) using a two-chamber method. We find that the nitrogen flow obeys the Cha and McCoy theory with values of the tangential momentum accommodation coefficient (TMAC) α= 0.91 at small Kn and α close to one at large Kn, consistent with the redefinition of α by Arya et al. We obtain fast transport of water vapour compared to the predictions from the Cha and McCoy theory over a range of pressures using the two-chamber method and a mass loss method. We attribute the excess flows to: (1) a thin adsorbed layer of chain-like water on the walls reducing the TMAC at low pressures; (2) liquid or two-phase flow appearing for inlet pressure close to saturation pressure. A theory for TMAC is developed based on the Langmuir adsorption. We measure interdiffusive flow rates of water vapour in atmospheric air for the first time using the mass loss method and compare experimental results with ideal gas interdiffusive flow theory. We find interdiffusive flows of water vapour in air agree with the theory except for the case where water vapour partial pressures are close to the saturation pressure. Liquid or two-phase flow causes an enhancement of the interdiffusive flow by up to three orders of magnitude. Using the available theories we predict the dominant flow types as a function of channel diameter and make recommendations on the moisture hermeticity testing in devices.
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Vey, Sibylle. "Bestimmung und Analyse des atmosphärischen Wasserdampfgehaltes aus globalen GPS-Beobachtungen einer Dekade mit besonderem Blick auf die Antarktis." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1199897148238-94043.
Full textAbstract:
Der Wasserdampfgehalt der Atmosphäre gehört zu den Hauptkontrolleuren des Treibhauseffektes und spielt eine Schlüsselrolle im globalen Energiekreislauf, wobei den Polargebieten als globale Wärmesenken eine besondere Bedeutung zukommt. Im Rahmen dieser Arbeit wurde aus Messungen des Global Positioning System (GPS) der integrierte Wasserdampfgehalt innerhalb der letzten Dekade bestimmt und analysiert. Die Untersuchungen stützen sich auf die Reprozessierung eines aus 195 Stationen bestehenden globalen GPS-Netzes. Die aus den geschätzten GPS-Troposphärenparameter bestimmten Wasserdampf- zeitreihen wurden hinsichtlich Genauigkeit und Homogenität untersucht. Nach Korrektion der Inhomogenit äten ist es möglich, mit GPS mehrjährige Schwankungen im potenziellen Niederschlagswasser mit einer Genauigkeit besser als 0,3 mm Höhe der Wassersäule zu erfassen. Als Ergebnis der Untersuchungen zeigen sich in Europa und großen Teilen Nordamerikas Anomalien des Wasserdampfgehaltes im Bereich eines Millimeters, welche sich vor allem auf thermodynamische Effekte zurückführen lassen. In den Tropen und im Südosten der USA können die Wasserdampfanomalien 3 bis 5 mm betragen. Sie sind durch dynamische Prozesse bedingt, die mit der Südlichen Oszillation im Zusammenhang stehen. Eine Anwendung der aus GPS-Beobachtungen bestimmten Wasserdampfzeitreihen ist die Validierung des Wasserdampfes im globalen Wettervorhersagemodell des National Center for Environmental Predicton (NCEP). Über Europa und großen Teilen Nordamerikas reproduziert NCEP die Schwankungen des Wasserdampfgehaltes sehr gut und stellt damit eine gute Datengrundlage für ?ächendeckende Untersuchungen langfristiger Veränderungen im Wasserdampfgehalt dar. In der Antarktis und den Tropen wird jedoch das saisonale und mehrjährige Signal des Wasserdampfes von NCEP um 25% bis 40% unterschätzt. Als zweite Anwendung der GPS-Wasserdampfzeitreihen erfolgt die Validierung satellitenbasierter Radiometermessungen über der Antarktis. Sie zeigt eine gute Übereinstimmung der Wasserdampfwerte aus GPSund Radiometermessungen. Die im Rahmen dieser Arbeit aus GPS-Beobachtungen bestimmten Wasserdampfzeitreihen bilden eine sehr gute Datengrundlage für weitergehende Untersuchungen der Wetter- und KlimaforschungThe atmospheric water vapour is one of the main variables controlling the greenhouse effect and it plays a crucial role in the global energy cycle. In this context the polar regions which act as global heat sinks are especially important. This study uses observations from the Global Positioning System (GPS) to investigate changes of the integrated atmospheric water vapour. It is based on a reprocessing of a global GPS network consisting of 195 stations. A strong emphasis was placed on the investigation of the accuracy and the homogeneity of the GPS derived water vapour time series. After correcting the inhomogeneities interannual ?uctuations in the precipitable water can be determined from GPS data with an accuracy of 0.3 mm in water column height. As a result, the interannual variations in the water vapour content are in the order of one millimetre over Europe and over large areas of North America. They are mainly related to thermodynamic effects. In the tropics and in the south east of the USA water vapour anomalies can reach 3 to 5 mm caused by dynamic processes connected to the Southern Oscillation. As one application of the estimated GPS water vapour time series a validation of water vapour from the global numerical weather prediction model of the National Center for Environmental Prediction (NCEP) was carried out. Over Europe and large parts of North America the seasonal signal and the interannual variations of the water vapour are very well reproduced by NCEP. Hence, in these regions NCEP presents a good database for area-wide investigations of long-term changes in the water vapour content. However, in Antarctica and in the Tropics the seasonal and also the interannual signals of the NCEP water vapour are strongly underestimated by 25% to 40%. A second application of the estimated GPS water vapour time series is the validation of satellite-based radiometer measurements over Antarctica. A good agreement was found between the water vapour derived from GPS and radiometer data. The water vapour time series estimated in this study provide a good basis for further weather and climate related investigations
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Pritchard, Tilsley. "Studies of minor constituents in the atmosphere." Thesis, University of Oxford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318870.
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Prillieux, Aurélien. "Hydrogen and water vapour effects on oxygen solubility and diffusivity in high temperature Fe-Ni alloys." Phd thesis, Toulouse, INPT, 2017. http://oatao.univ-toulouse.fr/18676/1/PRILLIEUX_Aurelien.pdf.
Full textAbstract:
It is a worldwide priority to reduce emissions of greenhouse gases such as CO2. One solution for reducing these emissions is to improve the efficiency of energy production units by increasing their operating temperature. However, in order to increase operating temperature, new austenitic materials based on the Fe-Ni-Cr system have to be designed. In addition, these materials need to exhibit good protection against high temperature oxidation, which is achieved by the formation of a slow growing chromium oxide or alumina scale on the metal. However, to predict the formation of a protective scale, knowledge of the oxygen permeability, the product of oxygen solubility and diffusivity, in the base alloy is required. The objective of this study is to measure the permeability, solubility and diffusivity of oxygen in Fe- Ni alloys at temperatures above 1,000°C. In order to obtain the best results, the formation of an external oxide layer during the experiment has to be avoided. To achieve this, the oxygen partial pressure was fixed at the Fe/FeO equilibrium pressure in all experiments. In addition, two types of atmospheres were used: one dry and one wet, in order to investigate the effect of water vapour on oxygen permeability, solubility and diffusivity. The dry atmosphere was achieved using the Rhines Pack technique. The samples were oxidised in vacuum-sealed quartz capsules, which contained a mixture of powdered iron and wüstite. The humid atmosphere was obtained by using H2/H2O gas mixtures with the appropriate water vapour to hydrogen ratio to fix oxygen partial pressure at the Fe/FeO equilibrium. The maximum oxygen solubility was found in pure iron, and decreased continuously with nickel additions to the alloy. The dependence of solubility on alloy composition is non-ideal, and cannot be predicted from simple models. Moreover, the presence of water vapour in the atmosphere seems to increase the solubility by a factor of 2 in alloys with nickel content lower than 80 at.% at temperatures near 1,000°C. However, at 1,150°C the solubility of the oxygen is independent of the environment. The oxygen permeability was determined by measuring the internal oxidation kinetics of Fe-Ni-Cr alloy. These kinetics were evaluated by measuring the internal oxidation zone depth by optical microscopy, or by continuous and discontinuous thermogravimetry. Results showed that the oxygen permeability exhibits the same variation with alloy composition as the oxygen solubility, independent of the atmosphere. In particular, no significant effect of water vapour on oxygen permeability values was observed. In the present study, the oxygen diffusion coefficient was also determined using permeability, in addition to the independent measurement of the oxygen solubility carried out in the present study. For temperature above 1,000°C, the variation of oxygen diffusion coefficient with the alloy composition is similar in all environments tested, and a maximum is observed for alloys with a nickel content of 40 at.%. However, for a given nickel content up to 60 at.%, the presence of water vapour in the atmosphere decreases the value of the oxygen diffusion coefficient by a factor of 2-3 at 1,000°C. In addition, this difference between diffusion coefficients measured in a dry and wet atmosphere increases as the temperature decreases. Overall, it was found that the water vapour has no effect on the way in which oxygen permeability, solubility and diffusivity vary with the alloy composition. However, the presence of water vapour in the environment appears to increase the oxygen solubility and decrease the oxygen diffusivity in iron-rich alloys, the effect being more significant at low temperatures. These results suggest further research into interactions between O, H and metal vacancies, particularly for temperature around 1,000°C and below, as the latter defect is thought to change the diffusion and solubility properties of interstitial species.