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1
Saha, Gopal. „Studies on low and high energy particles in cosmic ray extensive air showers observed in the earths atmosphere“. Thesis, University of North Bengal, 1997. http://hdl.handle.net/123456789/684.
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2
Maitra, Santanu Nandan. „Investigation of relative course of Ozone depletion in earths atmosphere and its effects on environment“. Thesis, University of North Bengal, 2000. http://hdl.handle.net/123456789/586.
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3
James, Alexander. „Impacts of meteoric material on Earth's atmosphere : laboratory studies with atmospheric implications“. Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/16617/.
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Analogues were developed for Interplanetary Dust Particles (IDPs) and Meteoric Smoke Particles (MSPs). Candidate materials were characterised and compared to the present understanding of the nature of IDPs and MSPs. Knowledge and understanding from meteoritics was used to inform open questions in atmospheric chemistry. The elemental composition, structural, surface and size distribution properties of the candidates was compared to micrometeorites and remote measurements of MSPs. Both relatively rare carbonaceous and the more common ordinary chondritic meteorites and terrestrial minerals were shown to be useful analogues for IDPs, whilst synthetic materials were identified as analogues for MSPs. Uptake of HNO3 and HO2, based on laboratory experiments, was implemented in a global modelling study. The uptake processes were assessed to determine the region(s) and season(s) in which they would affect atmospheric chemistry. This heterogeneous chemistry augmented previous understanding of gas-phase chemistry, with a view to understanding all sources and sinks of atmospheric species. Whole Atmosphere Community Climate Model (WACCM) runs including uptake were compared to control runs with only gas-phase chemistry. Uptake of both HNO3 and HO2 was shown to alter chemistry in the polar vortex, including effects on many secondary species and feedbacks on each other. Heterogeneous nucleation kinetics of nitric acid hydrates in Polar Stratospheric Clouds (PSCs) was investigated in the laboratory. SiO2 particles were used as analogues for MSPs processed in acidic solution and the phase which formed was investigated. A newly developed drop freeze assay capable of quantifying heterogeneous nucleation kinetics was used. Nucleation events observed in μl droplets were parameterised using current theoretical models and the results compared to atmospheric observations. The measured heterogeneous nucleation kinetics of the Dihydrate, which then readily converts to the Trihydrate, on SiO2 were shown to be capable of explaining the concentrations of crystals observed in the atmosphere.
4
Brissaud, Quentin. „Modélisation numérique des ondes atmosphériques issues des couplages solide/océan/atmosphère et applications“. Thesis, Toulouse, ISAE, 2017. http://www.theses.fr/2017ESAE0016/document.
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Cette thèse se penche sur la propagation d’ondes au sein du système coupléTerre-océan-atmosphère. La compréhension de ces phénomènes a une importance majeure pour l’étude de perturbations sismiques et d’explosions atmosphériques notamment dans le cadre de missions spatiales planétaires. Les formes d’ondes issues du couplage fluide-solide permettent d’obtenir de précieuses informations sur la source du signal ou les propriétés des milieux de propagation. On développe donc deux outils numériques d’ordre élevé pour la propagation d’ondes acoustiques et de gravité. L'u en différences finies et se concentre sur le milieu atmosphérique et la propagation d’ondes linéaires dans un milieu stratifié visqueux et avec du vent. Cette méthode linéaire est validée par des solutions quasi-analytiques reposant sur les équations de dispersion dans une atmosphère stratifiée. Elle est aussi appliquée à deux cas d’études : la propagation d’ondes liée à l’impact d’une météorite à la surface de Mars (mission NASA INSIGHT), et la propagation d’ondes atmosphériques liées au tsunami de Sumatra en 2004. La seconde méthode résout la propagation non-linéaire d’ondes gravito-acoustiques dans une atmosphère couplée, avec topographie, à la propagation d’ondes élastiques dans un solide visco-élastique. Cette méthode repose sur sur le couplage d’une formulation en éléments finis discontinus, pour résoudre les équations de Navier-Stokes la partie fluide, par éléments finis continus pour résoudre les équations de l’élastodynamique dans la partie solide. Elle a été validée grâce à des solutions analytiques ainsi que par des comparaisons avec les résultats de la méthode par différences finiesThis thesis deals with the wave propagation problem within the Earth-ocean-atmosphere coupled system. A good understanding of the these phenomena has a major importance for seismic and atmospheric explosion studies, especially for planetary missions. Atmospheric wave-forms generated by explosions or surface oscillations can bring valuable information about the source mechanism or the properties of the various propagation media. We develop two new numerical full-wave high-order modeling tools to model the propagation of acoustic and gravity waves in realistic atmospheres. The first one relies on a high-order staggered finite difference method and focus only on the atmosphere. It enables the simultaneous propagation of linear acoustic and gravity waves in stratified viscous and windy atmosphere. This method is validated against quasi-analytical solutions based on the dispersion equations for a stratified atmosphere. It has also been employed to investigate two cases : the atmospheric propagation generated by a meteor impact on Mars for the INSIGHT NASA mission and for the study of tsunami-induced acoutic and gravity waves following the 2004 Sumatra tsunami. The second numerical method resolves the non-linear acoustic and gravity wave propagation in a realistic atmosphere coupled, with topography, to the elastic wave propagation in a visco-elastic solid. This numerical tool relies on a discontinuous Galerkin method to solve the full Navier-Stokes equations in the fluid domain and a continuous Galerkin method to solve the elastodynamics equations in the solid domain. It is validated against analytical solutions and numerical results provided by the finite-difference method
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Alei, Eleonora. „Habitability Studies of Super Earths atmospheres“. Doctoral thesis, Università degli studi di Padova, 2019. http://hdl.handle.net/11577/3422351.
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Over the centuries, mankind always wondered whether other worlds existed, as well as other life forms upon their surfaces. This topic was considered “science-fiction” a few decades ago, but now it’s becoming more and more realistic: actually, different planets do exist, and some of them could bear life. Up to date, a database of more than 7000 planets or candidates is continuously updated, as current facilities keep on discovering new ones – a simple estimate suggests that in our galaxy tens of billions of new planets await to be revealed. Being extrasolar planetology a relatively new field of astrophysics, many things need to be set and done. In this case, a full characterization of the different atmospheres terrestrial exoplanets are likely to have is needed to correctly understand observational data; also, one should retrieve information about their formation and be able to presume that some form of life exists on the surface. To do that, theoretical modeling is needed: by simulating a simple imaginary exoplanet, one could have a better understanding of how all active processes interact within the system and what observable features they express so that they could be recognized when observing a real exoplanet. In this Ph.D. project, I explored the topic in various ways, starting with an overview about the detection techniques, the current knowledge about Super Earths, which are massive terrestrial exoplanets, and the concept of habitability. In the framework of a standardized, Virtual Observatory (VO) aware treatment of the exoplanets, I developed Exo-MerCat, which collects data from the most important online archives and merges the information while correcting nomenclature, status, and coordinate issues. This catalog is now a VO resource and has been positively accepted by the International Virtual Observatory Alliance (IVOA), as well as being used for PLATO and ARIEL space missions. Exo-MerCat allowed retrieving the sample of known Super Earths, which is then used as input to create a grid of atmospheric models to be run with the 1D radiative-convective model MAGRATHEA which I contributed to develop. MAGRATHEA can model Earth and Mars-like atmospheres, covering a wide range of the physical and chemical parameter space. It is able to calculate the radiative-convective equilibrium solution of an atmosphere in a very short time (a few hours of computational time), allowing us to fulfill a grid of 18000 atmospheric models of theoretical planets and 2400 ones of observed planets, as retrieved by the Exo-MerCat catalog. These models can be useful to study under which physical and atmospheric conditions it is possible to find liquid water on the surface of the planet, an essential requirement for the habitability of exoplanets. The atmospheric pressure-temperature profiles for the observed Super Earths grid, as retrieved by MAGRATHEA, were then used as an input for the Exoplanet Ozone Model to produce the corresponding ozone profile. The code is, at present, still at its early stages, but can efficiently produce the ozone profile of an atmosphere by solving the (photo-induced and thermal) chemistry of the oxygen-related species. The laboratory experiments performed at the Biology Department of the University of Padua, within the “Atmosphere in a Test-Tube project”, can benefit from the theoretical results from MAGRATHEA. The physical and chemical conditions at the surface are reproduced in the laboratory, forming exotic environments at which cyanobacteria are exposed. The study of the survival rate and the variation of the chemical composition caused by the presence of biological activity can be thus performed: this is indispensable in order to understand if, and when, a habitable planet can be actually inhabited.Nei secoli, ci siamo sempre chiesti se esistessero altri mondi e altre forme di vita sulla superficie di questi. Questo argomento è stato considerato spesso “fantascienza” fino a pochi decenni fa, ma ora sta diventando sempre più realistico: in realtà, pianeti diversi esistono ed alcuni di essi possono ospitare la vita. Ad oggi, un archivio di più di 7000 pianeti confermati o candidati è costantemente aggiornato, al passo con gli strumenti che ne scoprono sempre di più - solo nella nostra Galassia, decine di miliardi di nuovi pianeti aspettano di essere scoperti. Essendo la planetologia extrasolare un campo relativamente nuovo dell'astrofisica, molte cose devono essere ancora studiate. In questo caso, una caratterizzazione più dettagliata delle possibili atmosfere di esopianeti di tipo terrestre è necessaria per comprendere meglio le osservazioni; inoltre, bisognerebbe ricavare informazioni sulla loro formazione e poter presumere se, ed in quali casi, forme di vita potrebbero esistere su quei pianeti. Per fare ciò, un approccio teorico è necessario: simulando un pianeta in maniera semplificata, si potrebbe avere una migliore comprensione di come tutti i processi attivi interagiscono tra loro e quali osservabili producono, affinché possano essere identificate quando si osserva un vero esopianeta. In questo progetto di Dottorato, ho esplorato l'argomento da diversi punti di vista, iniziando con una sintesi dei metodi di scoperta, di ciò che è noto ad oggi sulle Super Terre (pianeti terrestri massivi), e del concetto di abitabilità. In una prospettiva di un trattamento standardizzato dei dati, il quale possa rientrare nei canoni del Virtual Observatory (VO), ho sviluppato Exo-MerCat al fine di collezionare dati dai più importanti archivi online, incrociando le informazioni e correggendo problemi di nomenclatura, status e coordinate. Questo catalogo è ora una risorsa VO ed è stato accettato positivamente dall'International Virtual Observatory Alliance (IVOA), oltre ad essere usato per le missioni spaziali PLATO e ARIEL. Exo-MerCat ha permesso di ricavare l'insieme di Super Terre note, usato poi per creare una griglia di modelli atmosferici utilizzata dal modello 1D radiativo-convettivo MAGRATHEA, che ho contribuito a sviluppare. MAGRATHEA riesce a riprodurre atmosfere di tipo terrestre e marziano, coprendo un largo intervallo di parametri fisici e chimici. Il codice calcola il profilo di equilibrio radiativo-convettivo di una atmosfera in poche ore di tempo computazionale, consentendoci di riempire una griglia di 18000 modelli di pianeti teorici e una di 2400 modelli di pianeti osservati, ricavati dall'insieme prodotto da Exo-MerCat. Questi modelli possono essere utili per studiare sotto quali condizioni fisiche e atmosferiche è possibile trovare acqua liquida sulla superficie di un pianeta, requisito essenziale per l'abitabilità degli esopianeti. I modelli atmosferici delle Super Terre osservate ricavati da MAGRATHEA sono stati usati come input per l'Exoplanet Ozone Model al fine di produrre la concentrazione di ozono corrispondente ai profili stessi. Questo codice è, al momento, ancora preliminare, ma può riprodurre il profilo dell'abbondanza di ozono di una atmosfera risolvendo la chimica foto-indotta e termica delle specie legate all'ossigeno. I risultati teorici ottenuti dai vari codici sono utili agli esperimenti di laboratorio effettuati al Dipartimento di Biologia dell'Università di Padova. Considerando alcune atmosfere calcolate da MAGRATHEA, si possono riprodurre le condizioni fisiche e chimiche alla superficie in laboratorio, formando atmosfere esotiche ed esponendo cianobatteri a queste. Lo studio della sopravvivenza e dell'adattamento dei batteri, così come della variazione della composizione chimica causata dall'attività biologica, può essere eseguito. Ciò è indispensabile per comprendere se, e sotto quali condizioni, un pianeta abitabile può essere effettivamente abitato.
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Annaloro, Julien. „Elaboration of collisional-radiative models applied to atmospheric entry into the Earth and Mars atmospheres“. Phd thesis, Université de Rouen, 2013. http://tel.archives-ouvertes.fr/tel-00915497.
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L'entrée hypersonique d'un objet dans la haute atmosphère d'une planète entraîne la création d'un plasma à la suite de la compression très intense du gaz incident à l'objet. Cette compression s'effectue dans une couche de choc présentant une grande richesse en déséquilibres dont la méconnaissance limite notre capacité à prédire avec précision les contributions convective, radiative et catalytique de la densité de flux d'énergie pariétale, pourtant cruciale pour l'optimisation du dimensionnement du système de protection thermique de l'objet. Les contributions précédentes dépendent fortement des densités de population des états excités qui échappent à un comportement de type boltzmanien et présentent une distribution dépendant des phénomènes élémentaires collisionnels et radiatifs. Dans ces circonstances, le but de ces travaux était d'étudier, dans les situations d'entrée dans l'atmosphère de Mars et de la Terre, le comportement des états excités de mélanges complexes (CO2 -N2 -Ar et N2 -O2 -Ar, respectivement) basée sur le développement de modèles collisionnels-radiatifs (CR) électro-vibrationnels spécifiques. Deux modèles CR ont ainsi été développés : CoRaM-MARS pour l'atmosphère martienne (22 espèces, 10^6 processus élémentaires) et CoRaM-AIR pour l'atmosphère terrestre (13 espèces, 500000 processus élémentaires). Ces modèles, mis en œuvre dans une approche lagrangienne à pression et température constantes dans des conditions thermodynamiques représentatives des situations d'entrée (notamment le cas FIRE II pour les entrées terrestres), ont montré que le rayonnement présente une influence très faible sur la cinétique des mélanges étudiés et que les écarts à la distribution de Boltzmann sont systématiques. Le très grand nombre d'états à prendre en compte interdit une intégration directe des modèles CR précédents dans des codes aérodynamiques. Cependant, une réduction à l'azote de ces modèles a été réalisée. Le modèle CR ainsi constitué (CoRaM-N2 , 5 espèces, 150 états, 40000 processus élémentaires) a été intégré à un code eulérien traitant les écoulements monodimensionnels d'après-choc ou de tuyère divergente. L'accord avec des résultats expérimentaux acquis en tube à choc à fort nombre de Mach est très satisfaisant. Pour des applications 2D ou 3D, des taux globaux ont par ailleurs été déterminés théoriquement pour (1) l'ionisation/recombinaison par impact électronique de l'azote, de l'oxygène, du carbone et de l'argon, (2) la dissociation/recombinaison de N2 , O2 par impact de N, N2 , O, O2 et (3) la dissociation/recombinaison de CO2 par impact de lourd. La comparaison avec des résultats expérimentaux montre un accord en général très satisfaisant. Les taux directs et inverses étant calculés de manière indépendante, il est montré que leur rapport s'écarte de la constante d'équilibre globale correspondante à mesure que la température augmente.
7
Morris, Paul. „Remote sensing of the Earth's atmosphere“. Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.317735.
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8
Mantini, Jennifer Lynn. „A LABORATORY INVESTIGATION OF THE STRUCTURE OF TORNADO-LIKE VORTICES THROUGH MEASUREMENT OF SURFACE PRESSURE“. Miami University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=miami1218653459.
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9
Schofield, Daniel Paul, und n/a. „Hydrated complexes in the earth�s atmosphere“. University of Otago. Department of Chemistry, 2005. http://adt.otago.ac.nz./public/adt-NZDU20070427.120933.
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The interaction between sunlight and our atmosphere is one of the most fundamental processes affecting weather and climate. The majority of the Sun�s radiation is produced in the ultraviolet, visible and near-infrared regions of the electromagnetic spectrum. These spectral regions correspond to the energies of vibrational overtone and electronic transitions. The composition of our atmosphere is complex, and many trace species have a large influence on its chemistry and dynamics. Hydrogen bound hydrated complexes are trace species that could play an important role in the Earth�s atmosphere. However, before this role can be quantified, spectral identification and characterisation of these complexes is essential.
We have developed vibrational local mode Hamiltonians to simulate the absorption spectra of hydrated complexes. To test the approximations made in the vibrational model, we have peformed calculations on the diatomics OH, HF and CO, which can be considered to act as pure local modes. When highly correlated ab initio methods and large basis sets are used to calculate the potential energy and dipole moment curve, the simulated vibrational transitions of the diatomics are in excellent agreement with experiment.
We have derived approximate vibrational Hamiltonians which describe the OH-stretching and HOH-bending modes of vibration in the complexes H₂O�H₂O, H₂O�HO₂ and H₂O�HO. The calculated spectrum of H₂O�H₂O has been used to assess its atmospheric importance, and to succesfully guide experimental efforts to detect H₂O�H₂O in the laboratory and the Earth�s atmosphere. The calculated transition energies and intensities of H₂O�H₂O and H₂O�HO are in good agreement with experimental matrix isolation and gas-phase studies.
To investigate the effect of low frequency modes on OH-stretching overtone spectra we have simulated the spectrum of HOONO. We have derived a Hamiltonian that couples the NOOH-torsional mode to the high frequency OH-stretching and OOH-bending modes. The simulated spectrum is in good agreement with the experimentally observed spectrum. We find that the OH-stretching spectra are perturbed strongly only if the barrier to torsion is low.
We have also investigated changes in the electronic spectrum of hydrated complexes and the corresponding parent monomers. Upon complex formation, the lowest-lying electronic transition in the hydroxyl radical is strongly redshifted outside the region of monomeric absorption.
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Kazil, Jan, Philip Stier, Kai Zhang, Johannes Quaas, Stefan Kinne, D. O'Donnell, Sebastian Rast et al. „Aerosol nucleation and its role for clouds and Earth’s radiative forcing in the aerosol-climate model ECHAM5-HAM“. Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-185342.
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Nucleation from the gas phase is an important source of aerosol particles in the Earth’s atmosphere, contributing to the number of cloud condensation nuclei, which form cloud droplets. We have implemented in the aerosolclimate model ECHAM5-HAM a new scheme for neutral and charged nucleation of sulfuric acid and water based on laboratory data, and nucleation of an organic compound and sulfuric acid using a parametrization of cluster activation based on field measurements. We give details of the implementation, compare results with observations, and investigate the role of the individual aerosol nucleation mechanisms
for clouds and the Earth’s radiative forcing. The results of our simulations are most consistent with observations when neutral and charged nucleation of sulfuric acid proceed throughout the troposphere and nucleation due to cluster activation is limited to the forested boundary layer. The globally averaged annual mean contributions of the individual
nucleation processes to total absorbed solar short-wave radiation
via the direct, semi-direct, indirect cloud-albedo and cloud-lifetime effects in our simulations are −1.15 W/m2 for charged H2SO4/H2O nucleation, −0.235 W/m2 for cluster activation, and −0.05 W/m2 for neutral H2SO4/H2O nucleation. The overall effect of nucleation is −2.55 W/m2, which exceeds the sum of the individual terms due to feedbacks
and interactions in the model. Aerosol nucleation contributes over the oceans with −2.18 W/m2 to total absorbed solar short-wave radiation, compared to −0.37 W/m2 over land.
We explain the higher effect of aerosol nucleation on Earth’s radiative forcing over the oceans with the larger area covered by ocean clouds, due to the larger contrast in albedo between clouds and the ocean surface compared to continents, and the larger susceptibility of pristine clouds owing to the saturation of effects. The large effect of charged nucleation in our simulations is not in contradiction with small effects seen in local measurements: over southern Finland, where cluster activation
proceeds efficiently, we find that charged nucleation of sulfuric acid and water contributes on average less than 10% to ultrafine aerosol concentrations, in good agreement with observations.
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Kataria, Tiffany. „Atmospheric Circulation of Hot Jupiters and Super Earths“. Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/338971.
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This dissertation explores the atmospheric circulation of extrasolar planets ranging from hot Jupiters to super Earths. For each of these studies, I utilize a three-dimensional circulation model coupled to a state-of-the-art, plane-parallel, two-stream, non-grey radiative transfer model dubbed the SPARC/MITgcm. First, I present models of the atmospheric circulation of eccentric hot Jupiters, a population which undergoes large variations in flux throughout their orbits. I demonstrate that the eccentric hot Jupiter regime is qualitatively similar to that of planets on circular orbits. For a select number of model integrations, I generate full-orbit lightcurves and find that the timing of transit and secondary eclipse viewed from Earth with respect to periapse and apoapse can greatly affect what is seen in infrared (IR) lightcurves. Next, I present circulation models of WASP-43b, a transiting hot Jupiter that is joining the ranks of HD 189733b and HD 209458b as a 'benchmark' hot Jupiter, with a wide array of observational constraints from the ground and space. Here I utilize the robust dataset of spectrophotometric observations taken with the Wide Field Camera 3 (WFC3) aboard the Hubble Space Telescope (HST) to interpret my model results. I find that an atmospheric composition of 5x solar provides the best match to the data, particularly in emission. Lastly, I present atmospheric simulations of the super Earth GJ 1214b, exploring the planet's circulation as a function of atmospheric metallicity and composition. I find that atmospheres with a low mean-molecular weight have strong day-night temperature variations at pressures above the infrared photosphere that lead to equatorial superrotation. For these atmospheres, the enhancement of atmospheric opacities with increasing metallicity leads to shallower atmospheric heating, larger day-night temperature variations and hence stronger superrotation. In comparison, atmospheres with a high mean-molecular weight have larger day-night and equator-to-pole temperature variations than low mean-molecular weight atmospheres, but differences in opacity structure and energy budget lead to differences in jet structure. By comparing emergent flux spectra and lightcurves for 50x solar and water-dominated compositions, I show that observations in emission can break the degeneracy in determining the atmospheric composition of GJ 1214b. In sum, these three studies explore exoplanet atmospheric circulation as a function of mass, radius, gravity, rotation rate, eccentricity and orbital distance.
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Arnold, Nathan Patrick. „Atmospheric Superrotation in Warm Earth Climates“. Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:11213.
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This thesis considers atmospheric superrotation, a state of westerly equatorial winds which must be maintained by up-gradient eddy momentum fluxes. Superrotation has appeared in simulations of warm climates that generate enhanced Madden-Julian Oscillation (MJO)-like variability. This led to hypotheses that the warmer atmospheres of the early Pliocene and Eocene may have been superrotating, and that the phenomenon may be relevant to future climate projections.Earth and Planetary Sciences
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Whalley, Charlotte Louise. „Magnesium chemistry in the upper atmosphere of Earth and Mars“. Thesis, University of Leeds, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.551263.
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Ablation of cosmic dust causes the deposition of metals into the upper atmospheres of Earth and Mars between 80 -120 km. Magnesium is one of the most abundant metals in this dust and large concentrations have been observed in the terrestrial atmosphere. Kinetic measurements have been made of the reactions of Mg- and Mg+- containing species with relevant atmospheric constituents using a pulsed laser photolysis-laser induced fluorescence technique and a fast flow tube. The resulting rate coefficients were then input into a 1-dimensional atmospheric model in order to test them against mid-latitude satellite observations of the Mg and Mg+ layers. The model was able to replicate the main observations such as peak concentration, peak height, Mg depletion and seasonal variation. In the Martian atmosphere radio occultation measurements have observed a third sporadic layer of electrons. It has been suggested that this electron layer could indicate a layer of Fe+ and Mg+ ions in analogy with the terrestrial atmosphere. However, it would be expected that in the CO2-rich Martian atmosphere metal ions would be rapidly neutralised. Experimental studies of the effectiveness of CO2 as a third-body in pressure dependant Mg+ reactions were undertaken in a PLP-L1F system. These measurements were combined with the rate coefficients measured in the earlier work to model the lifetime of metal ions within the atmosphere of Mars. The model was able to replicate the observations and found the sporadic third layer to consist mainly of Mg+.
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Kazil, Jan, Philip Stier, Kai Zhang, Johannes Quaas, Stefan Kinne, D. O''Donnell, Sebastian Rast et al. „Aerosol nucleation and its role for clouds and Earth’s radiative forcing in the aerosol-climate model ECHAM5-HAM“. Copernicus Publication, 2010. https://ul.qucosa.de/id/qucosa%3A13791.
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Nucleation from the gas phase is an important source of aerosol particles in the Earth’s atmosphere, contributing to the number of cloud condensation nuclei, which form cloud droplets. We have implemented in the aerosolclimate model ECHAM5-HAM a new scheme for neutral and charged nucleation of sulfuric acid and water based on laboratory data, and nucleation of an organic compound and sulfuric acid using a parametrization of cluster activation based on field measurements. We give details of the implementation, compare results with observations, and investigate the role of the individual aerosol nucleation mechanisms
for clouds and the Earth’s radiative forcing. The results of our simulations are most consistent with observations when neutral and charged nucleation of sulfuric acid proceed throughout the troposphere and nucleation due to cluster activation is limited to the forested boundary layer. The globally averaged annual mean contributions of the individual
nucleation processes to total absorbed solar short-wave radiation
via the direct, semi-direct, indirect cloud-albedo and cloud-lifetime effects in our simulations are −1.15 W/m2 for charged H2SO4/H2O nucleation, −0.235 W/m2 for cluster activation, and −0.05 W/m2 for neutral H2SO4/H2O nucleation. The overall effect of nucleation is −2.55 W/m2, which exceeds the sum of the individual terms due to feedbacks
and interactions in the model. Aerosol nucleation contributes over the oceans with −2.18 W/m2 to total absorbed solar short-wave radiation, compared to −0.37 W/m2 over land.
We explain the higher effect of aerosol nucleation on Earth’s radiative forcing over the oceans with the larger area covered by ocean clouds, due to the larger contrast in albedo between clouds and the ocean surface compared to continents, and the larger susceptibility of pristine clouds owing to the saturation of effects. The large effect of charged nucleation in our simulations is not in contradiction with small effects seen in local measurements: over southern Finland, where cluster activation
proceeds efficiently, we find that charged nucleation of sulfuric acid and water contributes on average less than 10% to ultrafine aerosol concentrations, in good agreement with observations.
15
Goodman, Jason (Jason Curtis) 1973. „Interannual middle-latitude atmosphere-ocean interactions“. Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/16779.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2001.Includes bibliographical references (p. 144-151).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
This thesis discusses the interaction of atmosphere and ocean in midlatitudes on interannual and decadal timescales. We investigate the extent to which mutuallycoupled atmosphere-ocean feedback can explain the observed coupled variability on these timescales, and look for preferred modes of atmospheric response to forcing by sea-surface temperature anomalies. First, we formulate and study a very simple analytical model of the mutual interaction of the middle-latitude atmosphere and ocean. The model is found to support coupled modes in which oceanic baroclinic Rossby waves of decadal period grow through positive coupled feedback between the thermal forcing of the atmosphere induced by associated SST anomalies and the resulting windstress forcing of the ocean. Growth only occurs if the atmospheric response to thermal forcing is equivalent barotropic, with a particular phase relationship with the underlying SST anomalies. The dependence of the growth rate and structure of the modes on the nature of the assumed physics of air-sea interaction is explored, and their possible relation to observed phenomena discussed. We then construct a numerical model with the same physics; this enables us to consider the effects of nontrivial boundary conditions and background flows within the model. We find that the finite fetch of a closed ocean basin reduces growth rate and can lead to decay. However, the coupled mode described above remains the least-damped, and is thus the pattern most easily energized by stochastic forcing. Using a non-uniform atmospheric background flow focuses perturbation energy into particular areas, so that the coupled mode's expression in the atmosphere becomes fixed in space, rather than propagating. This improves the mode's resemblance to observed patterns of variability, such as the North Atlantic Oscillation, which are generally stationary patterns which fluctuate in intensity. The atmospheric component of the coupled mode exists in a balance between Rossby-wave propagation and vorticity advection. This is the same balance as the "neutral vectors" described by Marshall and Molteni (1993). Neutral vectors are the right singular vectors of the linearized atmospheric model's tendency matrix that have the smallest eigenvalues; they are also the patterns that exhibit the largest response to forcing perturbations in the linear model. We explain how the coupled mode arises as the ocean excites atmospheric neutral vectors. Neutral vectors act as pattern-specific amplifiers of ocean SST anomalies. We then proceed to study the neutral vectors of a quasigeostrophic model with realistic mean flow. We find a striking similarity between these patterns and the dominant patterns of variability observed in both the full nonlinear model and in the real world. We provide a mathematical explanation for this connection. Investigation of the "optimal forcing patterns" - the left singular vectors - proves to be less fruitful. The neutral modes have equivalent barotropic vertical structure, but their optimal forcing patterns are baroclinic and seem to be associated with low level heating. But the horizontal patterns of the forcing patterns are not robust, and are sensitive to the form of the inner product used in the SVD analysis. Additionally, applying "optimal" forcing patterns as perturbations to the full nonlinear model does not generate the response suggested by the linear model.
by Jason Goodman.
Ph.D.
16
Olkin, Catherine Blair. „Stellar occultation studies of Triton's atmosphere“. Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/55046.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1996.Includes bibliographical references (p. 127-136).
by Catherine Blair Olkin.
Ph.D.
17
Salyk, Colette Vanessa. „Stellar occultation investigations of Pluto's atmosphere“. Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/114110.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2003.Cataloged from PDF version of thesis. Page 21 missing from original thesis.
Includes bibliographical references (pages 27-28).
We investigate the shape of Pluto's atmosphere using data from the occultation of the V=15.7 star P131.1 by Pluto on 2002 Aug 21 (UT). We find that Pluto's atmosphere, as projected onto the sky, is noticeably non-circular. This implies an overall ellipsoidal shape, which could be an indication of high winds and/or latitudinal stratification. We decide to compare our results to those obtained from datasets of the occultation of P8 by Pluto on 1988 June 9 (UT). Previous analyses of these datasets by Millis et al. (1993) had led to the conclusion that Pluto's atmospheric shape did not deviate from that of a sphere. However, we find that the 1988 datasets do not conclusively demonstrate that this is the case. We conclude that Pluto's atmosphere is currently non-spherical and could have been non-spherical at the time of the 1988 occultation. Implications for high winds and/or latitudinal stratification present exciting possibilities to be investigated by the upcoming New Horizons mission to Pluto.
by Colette Salyk.
S.B.
18
Liebmann, Janne. „Linking Atmospheric Oxygenation to the Deep Earth“. Thesis, Curtin University, 2020. http://hdl.handle.net/20.500.11937/82608.
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This thesis proposes a model for the co-evolution of the Earth’s interior and surface environment. Specifically, this model suggests that the emergence of continents above sea-level 2.4 billion years ago led to a flush of nutrients into the oceans providing a boost for photosynthetic bacteria. Eventually, these processes and concomitant changes in the composition of volcanic gases and weathering patterns led to the rise of oxygen in our atmosphere, enabling the development of complex life.
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Muller-Wodarg, Igo Carl Friedrich. „Modelling tides propagating through the menopause into the earth's upper atmosphere“. Thesis, University College London (University of London), 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268013.
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Ortega, San Martin Luis. „Where is the xenon that is missing from the Earth's atmosphere?“ Revista de Química, 2013. http://repositorio.pucp.edu.pe/index/handle/123456789/99511.
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El análisis químico de los meteoritos que más se parecen a la materia que dio lugar a la formación de la Tierra revela que la concentración del gas xenón en la atmósfera de nuestro planeta es menor de la que se debería esperar. Investigaciones recientes parecen indicar que el origen de esta deficiencia podría estar relacionado con la solubilidad de los gases nobles en las vacantes de oxígeno de la estructura perovskita del silicato de magnesio, MgSiO3, principal componente del manto terrestre.The chemical analysis of the meteorites considered to resemble closely the primordial matter which led to the formation of the Earth indicates that the concentration of xenon gas in our atmosphere is lower than expected. It seems that this deficiency is related to the noble gases’ solubility in the oxygen vacancies present in the perovskite structure of magnesium silicate, MgSiO3, the main constituent of the Earth’s mantle.
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Gelman, Sarah E. (Sarah Eva). „Mantle thermal evolution of tidally-locked super-earths“. Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/114370.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 37-41).
Most super-Earth (mass < 10M[mathematical symbol]) detection techniques are biased towards massive planets with close-in orbits. A planet's orbital decay timescale decreases with a lower semi-major axis, thereby providing a high probability of detecting exoplanets which are in tidal-lock with their star. We model the effect of fixed stellar flux on an Earth-like planet's mantle convection structure and evolution using an axisymmetric finite element fluid convection code, SSAXC. Three punctuating evolutionary steps have been identified. First, a sequence of three initial downwellings form at the antistellar point, the substellar point, and at the terminator. After approximately 250,000 years, lithospheric instabilities drip down into the mantle, inducing pervasive small scale convective cells. Finally, after 3.5 billion years of planetary evolution, a cold region (~ 300°C) develops at the antistellar point, spanning the depth of the mantle, and inducing a pseudo-Mode 1 convective pattern. Though initial models have focused on an incoming stellar flux equivalent to that at the Earth, we also discuss the possibility of steady-state partial magma oceans in the substellar region induced by higher stellar fluxes. We propose that, though these tidally-locked planets may not be considered habitable in general, they may contain locally habitable regions due to their variety of long-lived extreme environments.
by Sarah E. Gelman.
S.B.
22
Rappaport, Elliot D. „Understanding Weather: Phase Changes of Water in the Atmosphere“. Fogler Library, University of Maine, 2007. http://www.library.umaine.edu/theses/pdf/RappaportED2007.pdf.
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Cronin, Timothy (Timothy Wallace). „Land-atmosphere interaction and radiative-convective equilibrium“. Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/90605.
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Thesis: Ph. D. in Climate Physics and Chemistry, Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2014.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 161-171).
I present work on several topics related to land-atmosphere interaction and radiative-convective equilibrium: the first two research chapters invoke ideas related to land-atmosphere interaction to better understand radiative-convective equilibrium; the last two research chapters use the framework of radiative-convective equilibrium to better understand land-atmosphere interaction. First, I calculate how averaging the incident solar radiation can lead to biases in idealized climate models. I derive an expression for the absorption-weighted solar zenith angle, which minimizes the bias in mean absorbed shortwave radiation, and I find that it is closely matched by the insolation-weighted zenith angle. Common use of daytime-weighted zenith angle likely leads to high biases in albedo by ~3%. Second, I explore the time scales of approach to radiative-convective equilibrium with both a simple linearized two-variable model, and a single-column model with full physics. I show that there is a long time scale of approach to radiative-convective equilibrium that is order hundreds of days even when the surface heat capacity vanishes. The impact of water vapor on the effective atmospheric heat capacity can more than double this time scale for warm temperatures and low surface heat capacities. Third, I develop an analytic theory for the sensitivity of near-surface temperature to properties of the land surface. I show that the theory compares well against a simple numerical model of the coupled boundary layer-surface system, as well as a more complex two-column model, and discuss application of the theory to questions of how changes in land use or ecosystem function may affect climate change. Finally, I find that the diurnal cycle of convection is important for the spatial distribution of rainfall in idealized simulations of radiative-convective equilibrium with a cloud-resolving model. In a region that is partly an island and mostly ocean, precipitation over the island falls primarily in a regular, strong, afternoon thunderstorm, with a time-mean rainfall rate more than double the domain average. I explore mechanisms for this island rainfall enhancement, investigate the importance of island size for my results, and find that the upper troposphere warms with the inclusion of an island, which may have implications for the large-scale tropical circulation.
by Timothy Cronin.
Ph. D. in Climate Physics and Chemistry
24
Wang, Xiaoli Ph D. Massachusetts Institute of Technology. „Global thermohaline circulation and ocean-atmosphere coupling“. Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/58357.
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Jansen, Malte F. (Malte Friedrich). „Equilibration of an atmosphere by geostrophic turbulence“. Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79329.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 183-187).
A major question for climate studies is to quantify the role of turbulent eddy fluxes in maintaining the observed atmospheric mean state. It has been argued that eddy fluxes keep the mid-latitude atmosphere in a state that is marginally critical to the deepest mode of baroclinic instability, which provides a powerful constraint on the response of the atmosphere to changes in external forcing. A similar criterion does, however not hold in the Southern Ocean, a region whose dynamics are otherwise very similar to the mid-latitude atmosphere. This thesis resolves this apparent contradiction, using a combination of theoretical considerations and eddy-resolving numerical simulations. It is shown that the adjustment of the extra-tropical troposphere to states of marginal criticality does not follow from a fundamental constraint, but is rather the result of the particular parameters characterizing Earth's troposphere. Both marginally critical and strongly supercritical zonal mean flows can be obtained in planetary atmospheres if external parameters are varied. We argue that changes in the equilibrated mean state over a wide range of simulations can better be understood in terms of a balance between the diabatic forcing and the eddy driven overturning circulation. Using a diffusive closure for the eddy flux of potential vorticity, we can relate the eddy-driven overturning transport to properties of the mean flow, and derive scaling relations for both the baroclinicity and vertical stratification of the equilibrated state.
by Malte F. Jansen.
Ph.D.
26
Cooray, Asantha Roshan. „Stellar occultation observations of Saturn's upper atmosphere“. Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/53030.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1997.Includes bibliographical references (leaves 74-79).
by Asantha Roshan Cooray.
M.S.
27
Foust, Jeffrey Alan 1971. „Stellar occultation studies of Saturn's upper atmosphere“. Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/9528.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1999.Includes bibliographical references (p. 224-230).
The properties of Saturn's upper atmosphere are not well-known despite several spacecraft flybys. However, the region of 1-100 [mu]bar can be studied in detail by observing stellar occultations -- when the planet passes in front of a star -- from ground-based or Earth-orbiting telescopes. We use data from five such occultations: three observed in 1995 by the Faint Object Spectrograph (FOS) on the Hubble Space Telescope (HST), one observed in 1996 at the NASA Infrared Telescope Facility (IRTF) and one in 1989 observed by a different instrument at the IRTF. The data span latitudes from 52° south to 75 ° north. We fit isothermal models to each data set and also perform numerical inversions. These analyses show that temperatures in the 1-10 [mu]bar range can vary significantly as a function of season and latitude, ranging from 121 to 160 K, in accordance with radiative transfer models for the atmosphere. We also search for evidence of gravity wave saturation in Saturn's upper atmosphere, as seen in other planetary atmospheres, by analyzing the power spectra of temperature and density data and by studying the temperature lapse rate in the atmosphere. Our analysis is consistent with saturated gravity waves for all data sets, although gravity wave saturation is not the sole explanation for the spectra. We take advantage of the wavelength-resolved HST FOS data to study the composition of Saturn's upper atmosphere. We measured the difference in feature times for data taken at two wavelengths, and use the different refractivities of hydrogen and helium, as a function of wavelength to compute the relative amounts of the two elements in the planet's atmosphere. We find that the helium mass fraction is 0.26 ± 0.10, higher than that found using Voyager data, but marginally consistent with theoretical models for the evolution of Saturn's atmosphere, although the large error bars on the results make a definitive conclusion problematic.
by Jeffrey Alan Foust.
Ph.D.
28
Anderson, Kelly Elizabeth. „Molecular simulation of earth systems from the atmosphere to the mantle“. Diss., Click on "Connect to Digital Dissertations", 2009. http://www.lib.umn.edu/articles/proquest.phtml.
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Chen, Jianli. „Geodynamical interconnections between the atmosphere, ocean, hydrosphere, cryosphere, and solid earth /“. Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
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30
Mauk, Rachel Grant. „Tropical Cyclone Formation in Environments with Cool SST and High Wind Shear over the Northeastern Atlantic Ocean (1975-2005)“. The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1275445016.
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Saunders, Russell W. „Laboratory studies of aerosol formation in the Earth's lower and upper atmosphere“. Thesis, University of East Anglia, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.433795.
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32
Donahue, Neil M. (Neil McPherson). „Nonmethane hydrocarbon chemistry in the remote marine atmosphere“. Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/52929.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1991.Vita.
Includes bibliographical references (p. 169-173).
by Neil McPherson Donahue.
Ph.D.
33
Reppert, Philip M. (Philip Miles) 1957. „Electrokinetics in the Earth“. Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/8851.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2000.Includes bibliographical references.
The study of Streaming potentials has applications in the earth sciences, ranging from fluid flow monitoring, to permeability determination, to studying the surface chemistry of rocks and minerals. In this thesis study of frequency-dependent electrokinetics is presented with both theoretical development and experimental verification. The complex (real and imaginary) streaming potential coupling coefficient is explained. This is followed by the first experiments to measure the real and imaginary part of frequency-dependent streaming potential coupling coefficients. As part of this study an experimental apparatus and data acquisition system were constructed to measure the streaming potential coupling coefficients as a function of frequency. The purpose of the experiments was to measure, for the first time, the real and imaginary part of streaming potentials. In addition, the measured frequency range was extended beyond any previous measurements. Frequency-dependent streaming potential experiments were conducted on one glass capillary, two porous glass filters, and one rock. The sample pore diameters ranged from 34 micrometers to 1 millimeter. Without these experiments, the validity of modeling of the frequency dependence of the seismoelectric effect using existing models streaming potential models would be in question. Two frequency- dependent models (Packard and Pride) were compared to the data. Both Pride's and Packard's models have a good fit to the experimental data in the low and intermediate frequency regime where viscous terms dominate in the fluid. In the high frequency regime, where inertial terms start to dominate, the data fits the theory after being corrected for capacitance effects of the experimental setup. Pride's generalized model appears to have the ability to more accurately estimate pore sizes in the porous medium samples. Packard's model has one unknown model parameter whereas Pride's model has four unknown model parameters, two of which can be independently determined experimentally. Pride's additional parameters may allow for a determination of permeability. As part of the study of frequency-dependent electrokinetics, this thesis presents the theory for frequency-dependent electro- osmosis. It is shown that the electro- osmosis frequency-dependent coupling coefficient is constant with increasing frequency until the critical frequency is reached, at which point the coupling coefficient starts to decrease with increasing frequency. The frequency response- electro- osmosiso- osmosis coupling coefficient is dependent on the capillary radius. The smaller the capillary radius the higher the critical frequency. Data is presented for a 0.127 mm capillary. In addition to studying frequency-dependent electrokinetics, this thesis examines the temperature-dependent behavior of streaming potential coupling coefficients. As part of this examination a review is made of the previous literature that discusses the temperature dependence of streaming potentials. The streaming potential coupling coefficient is determined using the permittivity, the conductivity, and the viscosity of the fluid. It has been determined that the temperature-dependent behavior of the permittivity, conductivity, and viscosity are well documented and do not alone account for temperature dependence of streaming potentials. The other quantity used in calculating the streaming potential coupling coefficient is the zeta potential. The temperature dependence of the zeta potential is not well understood at the present time. By examining the theory, it appears that the zeta potential temperature dependence is controlled by the fluid concentration and the adsorption properties of the surface. After examining the theory, streaming potential experiments at elevated temperature and pressure were conducted on Fontainebleau Sandstone, Berea Sandstone, and Westerly Granite. The experiments were conducted in a pressure vessel with temperatures ranging from 23° C to 200° C at pore pressure ranging from 20 bar to 50 bar and confining pressures ranging from 200 bar to 250 bar. The zeta potential was found to increase with increasing temperature, and the coupling coefficient can increase or decrease depending on how the conductivity of the sample varies. This implies that in geothermal regions, streaming potentials can have large magnitudes depending on the conductivity of the geothermal fluid.
by Philip M. Reppert.
Ph.D.
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Torres-Bello, Omar. „A simple zonal average energy budget model of the earth-atmosphere system“. Diss., Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/28033.
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Sallum, Stephanie E. „Pluto's atmosphere from the May 22, 2011 stellar occultation“. Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/114349.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 40-41).
This paper reports the observations and atmospheric fitting results from the May 22, 2011 stellar occultation by Pluto. Of the nine sites across the United States that attempted to observe the event, three obtained light curves at the predicted midtime without being clouded out. Simultaneous fitting of these three light curves utilizing a model fully detailed in Elliot and Young [1992] resulted in a best fit half-light radius of 1309 ± 25 km, a calculated temperature of 94 ± 4 K, and a calculated pressure scale height of 55 ± 2 km. These parameters, in the context of the previous occultations, reveal a trend in which Pluto's half-light radius has been increasing slightly since an initial dramatic increase between 1988 and 2002. While the pressure scale height has remained relatively constant, the temperature has decreased slightly over the recorded events. The changes in half-light radius agree with frost migration models in which Pluto's surface has a low thermal inertia [Hansen and Paige, 1996; Elliot et al., 2007], but further constraints on frost migration model parameters such as substrate and frost albedo, frost emissivity, and the supply of N2 require additional observations. The New Horizons spacecraft should encounter a dynamic atmosphere on Pluto during the scheduled fly by in 2015.
by Stephanie E. Sallum.
S.B.
36
Geiger, Felix [Verfasser]. „Fast-response measurements of organic trace species in the Earth's atmosphere / Felix Geiger“. Karlsruhe : KIT Scientific Publishing, 2015. http://www.ksp.kit.edu.
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Mashburn, Courtney Dyan. „Laboratory studies on the heterogeneous chemistry of clay minerals in the Earth's atmosphere“. Diss., Connect to online resource, 2006. 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:3239413.
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De, Pascuale Sebastian. „The plasmasphere extension of Earth's atmosphere: a perspective from the Van Allen probes“. Diss., University of Iowa, 2018. https://ir.uiowa.edu/etd/6405.
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Earth's plasmasphere persists as an extension of the ionosphere into space. The toroidal region of plasma is shaped by electric and magnetic forces in the terrestrial magnetosphere. As a dense population of cold plasma, the plasmasphere interacts with particles in the hot ring current and energetic radiation belts. Evolution of plasmaspheric density under the driving influence of the solar wind crosses many physical scales. Convective erosion during geomagnetic storms occurs on the order of hours, reducing the size of the plasmasphere by forming an abrupt plasmapause density gradient that varies in radial and diurnal location. The history of geomagntic activity determines the presence of morphological structures as small as notches and as large as plumes. Plasma of atmospheric origin is carried sunward by convection through drainage plumes towards the magnetopause where it can diminish the effectiveness of magnetic reconnection. Long-lived plumes are sustained by a higher rate of refilling than typically observed during plasmasphere recovery from geomagnetic disturbances. The response of the plasmasphere, then, is an integral part of the feedback cycle between the magnetosphere and ionosphere in the exchange of energy and particles.
This thesis aims to address three questions concerning the nature of the plasmasphere through the development of empirical and physics-based models under recent observations provided by the Van Allen Probes (RBSP-A & -B).
First, what is the distribution of density content in the plasmasphere? For a two year period with full MLT coverage by RBSP, the upper-hybrid resonance frequency in plasma wave spectra is used to identify sudden changes consistent with the plasmapause feature and to calculate the magnetic equatorial electron density. Plasmapause encounter radial locations for both spacecraft are correlated with a geomagnetic activity index showing significant scatter around a linear fit. On average, the predicted plasmapause location does account for the separation between the saturated plasmasphere and the depleted plasmatrough. A density threshold corresponding to the plasmapause boundary is used to sort RBSP measurements into these two classified plasma regions. Model profiles are developed for each region and compared to the results from previous missions. The importance of solar wind properties in regulating the severity of plasmasphere erosion is demonstrated.
Second, how does the plasmapause form and vary with geomagnetic activity? The two-dimensional plasmasphere density model, RAM-CPL, is employed to simulate two geomagnetic storms observed by the RBSP spacecraft. Inner-magnetospheric convection is parameterized by the Kp-index and solar wind properties. The performance of RAM-CPL is evaluated by the correspondence between virtual and actual plasmapause encounters. Overall, RAM-CPL achieved good agreement with RBSP observations of the plasmapause to within 0.5 L and measurements of electron density to within one order of magnetude inside the plasmasphere. An empirical model of ring current-ionosphere feedback was included to account for asymmetric erosion, but did not contribute significantly in the MLT sectors of interest when compared to electric field measurements. The difference in background activity level during quiet conditions between the two convection parameterizations was found to lead to 1 L difference in plasmapause location for each simulation trial. Solar wind driven simulations produce sharper and deeper erosion of the plasmapause at the onset of a geomagnetic storm, but also allow for larger recovery of the plasmasphere when compared to Kp-index driven simulations.
Third, what is the role of the ionosphere in sustaining the plasmasphere? Four geomagnetic events are observed by RBSP in opposing MLT sectors to exhibit undisturbed plasmasphere refilling following significant erosion of the plasmapause. RAM-CPL simulations of the strongest storm parameterized by solar wind properties shows the full evolution of plasmasphere density from the narrowing of a sunward plume at the onset of erosion, that begins to corotate into a duskside bulge as activity diminishes, to the outward recovery of the plasmapause over several days. A piecewise empirical model of plasmasphere refilling is composed from profiles of equatorial electron density and the observed correlation between the Kp-index and plasmapause location. The RAM-CPL timescale of refilling mediates the increase in density from plasmatrough to plasmasphere levels matching RBSP measurements during the quiet period after the storm. Density observations of the other geomagnetic events are consistent with reports of a two-stage refilling process.
39
Du, Toit Daniel N. J. „Low Earth orbit satellite constellation control using atmospheric drag“. Thesis, Link to the online version, 1997. http://hdl.handle.net/10019/2999.
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Wu, Jianghua. „Simulating northern peatland-atmosphere carbon dioxide exchange with changes in climate“. Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86815.
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About half of the global wetlands are located between 50-70° N, where climate change is projected to be greater than other regions. More than 95% of northern wetlands are peatlands. The majority of peatlands accumulate soil carbon (C) because, on average, net primary production (NPP) exceeds decomposition. Peatlands store ~ 450 G t soil carbon (1Gt C=1015 g C), a mass equivalent to about 20% of global terrestrial soil C, or half of atmospheric C. The carbon exchange between peatlands and the atmosphere is sensitive to climate variability and change because of the tight coupling with hydrology and ecosystem biogeochemistry. A critical question of this thesis is "Will northern peatlands continue to function as C sink under the projected climate change?"I use a modelling approach to answer this question. Firstly, a peatland C cycling model, the McGill Wetland Model (MWM), originally developed to simulate the C dynamics of ombrotrophic bogs, was modified, parameterized and evaluated for the simulation of the CO2 biogeochemistry of fens. Three modifications were made: (1) a function describing the impact of soil moisture on the optimal gross primary production (GPP); (2) a scheme to partition the peat profile into oxic and anoxic C compartments based on the effective root depth as a function of daily sedge NPP; and (3) a modified function describing the fen moss water dynamics. Secondly, I have examined the effect of bog microtopography on the simulation of ecosystem-level C cycling and found model processes scale linearly, so "parameter" upscaling can be used in regional scale assessments. Thirdly, I successfully evaluated a coupled Wetland version of Canadian Land Surface Scheme (CLASS3W) and MWM (called CLASS3W-MWM) for bogs and fens. The sensitivity analysis indicates that northern peatlands are thermally and hydrologically conservative and the combination of changes in temperature, precipitation and double CO2 concentration is much different than the sensitivity of peatlands to each environmental variable on their own.
Finally, I used CLASS3W-MWM to do a first-order experiment on how the CO2 exchange in northern peatlands might change under the changing climate. For future climate, I adjusted the site "measured" climate variables by the climate anomalies estimated by the CCCma-GCM3.0 for three time slices (2030, 2060 and 2100) using four different climate scenarios (A1B, A2, B1 and Commit). These simulations showed that bogs and fens have significantly different responses to climate change, particularly that fens are more sensitive to environmental change than bogs. At 2100, the bog remains a C sink for all the climate scenarios assessed because a significant increase in GPP still offset, to a smaller extent, the large increase in total ecosystem respiration (TER). However, by 2100, the fen switches to a C source for two scenarios (A1B and A2), due to a dramatic decrease in GPP and a significant increase in TER resulting from water stress linked to a large drop of water table depth.
Environ la moitié de l'ensemble des tourbières sont situées entre 50-70° N, là où les changements climatique prévus risquent d'être plus important que dans les autres régions. Plus de 95% des milieux humides nordiques sont des tourbières. La majorité des tourbières accumule du carbone (C) puisqu'en moyenne, la production nette primaire (NPP) excède la décomposition. Les tourbières accumulent environ 450 G t de C (1Gt C=1015 g C), une masse équivalente à environ 20% du C terrestre, ou la moitié du C atmosphérique. L'échange de C entre les tourbières et l'atmosphère est sensible aux changements climatiques et varie en fonction du lien entre leur hydrologie et la biogéochimie de l'écosystème. Une des questions critiques de cette thèse est « est-ce que les tourbières du nord demeureront des puits de C malgré les changements climatiques projetés? ».
J'utilise une approche de modélisation pour répondre à cette question. Premièrement, le modèle représentant le cycle du C dans les tourbière, le McGill Wetland Model (MWM), développé à l'origine pour simuler la dynamique du C dans les tourbières ombrotrophiques, a été modifié et les paramètres ajustés et évalués afin de simuler la biogéochimie du dioxide de carbone (CO2) des tourbières oligotrophiques. Trois modifications ont été faites : (1) une fonction décrivant l'impact de l'humidité du sol sur la production primaire brute (GPP) optimale; (2) un schéma pour partitionner le profil de la tourbière selon les compartiments oxiques et anoxiques du C basé sur la profondeur effective des racines en fonction de la NPP journalière du carex; et (3) une fonction modifiée décrivant la dynamique de l'eau de la tourbe en milieu oligotrophique. Deuxièmement, j'ai examiné l'effet de la microtopographie de la tourbière sur la simulation du cycle du C à l'échelle de l'écosystème et trouvé les processus du modèle à l'échelle linéaire, pouvant ainsi modifier les paramètres en changeant l'échelle utilisée pour l'évaluation à l'échelle régionale. Troisièmement, j'ai évalué avec succès une version couplée du modèle Canadian Land Surface Scheme (CLASS3W) et MWM, nommé (CLASS3W-MWM) pour les types de tourbières ombrotrophiques et oligotrophiques. L'analyse de sensibilité indique que les tourbières du nord sont conservatrices au niveau thermal et hydrologique et la combinaison du changement de température, de précipitation et une double concentration de CO2 est très différente par rapport à la sensibilité de chaque variable individuellement.
Finalement, j'ai utilisé le CLASS3W-MWM pour faire une expérience de premièr-ordre vérifiant comment l'échange de CO2 dans les tourbières du nord peuvent être modifiés sous un climat changeant. Pour les climats futurs, j'ai ajusté la variable climatique du site « mesuré » par les anomalies climatiques estimées par le CCma-GCM3.0 pour trois périodes de temps (2030, 2060 et 2100) en utilisant quatre différents scénarios climatiques (A1B, A2, B1 et Commit). Ces simulations ont montré que les tourbières oligotrophiques et ombrotrophiques ont des réponses significativement différentes aux changements climatiques, particulièrement les tourbières oligotrophiques, qui sont plus sensibles au changements environnementaux que les tourbières ombrotrophiques. En 2100, la tourbière ombrotrophique demeure un puits de C durant la totalité du scénario puisqu'une augmentation significative de la GPP compensait toujours, même si de manière moindre, l'augmentation importante de la respiration de l'écosystème (TER). Toutefois, en 2100, la tourbière oligotrophique est devenue une source de C pour deux scénarios (A1B et A2), dû à une diminution drastique de la GPP et une augmentation du TER résultant du stress hydrique lié à une grande diminution de la profondeur de la nappe phréatique. fr
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Blasch, Kyle William. „Analysis of the Earth's Schumann resonance“. Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/12122.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1994.Includes bibliographical references (p. [193]-[198]).
by Kyle William Blasch.
M.S.
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Ghent, Darren John. „Land surface modelling and Earth observation of land/atmosphere interactions in African savannahs“. Thesis, University of Leicester, 2011. http://hdl.handle.net/2381/10274.
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Land/atmosphere feedback processes play a significant role in determining climate forcing on monthly to decadal timescales. Considerable uncertainty however exists in land surface model representation of these processes. This investigation represents an innovative approach to understanding key land surface processes in African savannahs in the framework of the UK‘s most important land surface model – the Joint UK Land Environment Simulator (JULES). Findings from an investigation into the carbon balance of Africa for a 25-year period from 1982 to 2006 inclusive show that JULES estimated Africa to behave as a carbon sink for most of the 1980‘s and 1990‘s punctuated by three periods as a carbon source, which coincided with the three strongest El Niño events of the period. From 2002 until 2006 the continent was also estimated to be a source of carbon. Overall, the JULES simulation suggests a weakening of the African terrestrial carbon sink during this period primarily caused by hot and dry conditions in savannahs. Applying the model further, land surface temperature (LST) displayed large uncertainty with respect to savannah field measurements from Kruger National Park, South Africa, and JULES systematically underestimated LST with respect to Earth Observation data continent-wide. The postulation was that a reduction in the uncertainty of surface-to-atmosphere heat and water fluxes could be achieved by constraining JULES simulations with satellite-derived LST using an Ensemble Kalman Filter. Findings show statistically significant reductions in root mean square errors with data assimilation than without; for heat flux simulations when compared with Eddy Covariance measurements, and surface soil moisture when compared with derivations from microwave scatterometers. The improved representation of LST was applied to map daily fuel moisture content – one of the most important wildfire determinants - over the mixed tree/grass landscapes of Africa, whereby values were strongly correlated with field measurements acquired from three savannah locations.
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Baron, Richard Leigh. „Occultation astronomy and instrumentation : studies of the Uranian upper atmosphere“. Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/51472.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1989.Includes bibliographical references (leaves 207-208).
by Richard Leigh Baron.
Ph.D.
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Mazarico, Erwan Matías Alexandre 1981. „Study of the Martian upper atmosphere using radio tracking data“. Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/42923.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2008.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references.
Since the first in situ observations of the Martian atmosphere were made by the twin Viking landers, we have learned considerably more about its composition, dynamics and variability. Not only did the new data on global atmospheric densities generate opportunities to understand the atmospheric composition of early Mars and supply constraints at the upper limit of General Circulation Models, it is critical for the design and planning of future exploration missions. We can complement the successes of remote sensing and accelerometer investigations by using radio tracking data that have not been studied from an atmospheric science perspective, or are available for the first time. Due to the very low density of the higher layers atmosphere, the estimation of the drag acceleration using Precision Orbit Determination is a challenge. We developed new numerical models of the non-conservative forces acting on the spacecraft. In particular, the spacecraft crosssectional area is calculated using improved spacecraft macro-models which include interplate shadowing. These improvements in the force modeling enable a more robust estimation of the atmospheric density. The density structure from the middle atmosphere up to the exosphere is studied using radio tracking data from the Mars Odyssey and the Mars Reconnaissance Orbiter spacecraft. Measurements in the Martian middle atmosphere, near 100 -- 110 km, are obtained from the aerobraking phase of the Mars Odyssey spacecraft; we obtain periapsis density estimates consistent with the Accelerometer Team, and estimate scale heights representative of the drag environment from an operational point of view. The orbit of Mars Odyssey during its mapping and extended phases allows us to probe very high in the exosphere, near 400 km altitude. In the retrieved density time series, we observe some of the features of solar forcing and seasonal cycle predicted by different atmospheric models.
(cont.) The most recent radio tracking data, from the Mars Reconnaissance Orbiter mapping mission, enables a monitoring of densities near 250 -- 300 km at higher temporal and spatial resolutions, allowing a more detailed study than previously possible.
by Erwan Mazarico.
Ph.D.
45
Xu, Kuanman. „Vertical structure and the convective characteristics of the tropical atmosphere“. Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/57925.
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46
Gertler, Charles Garrison. „Extratropical storm tracks and the mean state of the atmosphere“. Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/129058.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2020Cataloged from student-submitted PDF of thesis.
Includes bibliographical references (pages 127-135).
The exact impacts of changes in the mean state of the atmosphere on the high-frequency phenomena that form the extratropical atmospheric circulation are uncertain. The extratropical storm tracks, regions of frequent extratropical cyclones, dominate weather in the extratropics, affecting the lives and livelihoods of billions of people. The results presented in this thesis connect changes in the mean state of the atmosphere to changes in the extratropical storm tracks. The Northern Hemisphere summer extratropical storm track has weakened in observations over the satellite era, while evidence indicates convective precipitation in the extratropics has concurrently increased. Using the concept of mean available potential energy (MAPE) partitioned into nonconvective and convective components, the second chapter of this thesis demonstrates that the changes in storm track strength and convection are consistent with changes in the temperature and humidity structure of the atmosphere.
Further, experiments with idealized atmospheres indicate how characteristic changes in surface temperatures over this period lead to diverging changes in the energy available to extratropical cyclones and their associated convection. In the third chapter of this thesis, the storm track strength is examined in solar geoengineering scenarios using results from climate models. The Northern Hemisphere extratropical storm track weakens in response to increased CO₂ by similar magnitudes regardless of whether solar geoengineering is used. In the Southern Hemisphere, the storm track strengthens in global warming scenarios, but weakens with solar geoengineering. Storm track intensity changes are shown to be consistent with changes in the structure of temperature and humidity using MAPE. In the fourth chapter of this thesis, a new method to calculate MAPE is introduced and used to perform the first exact MAPE calculations in a three-dimensional domain.
Further, an eddy-size restriction on the MAPE calculation is developed and introduced, which provides a measure of available energy that could be accessed locally by an extratropical cyclone. This approach is also used to identify the thermodynamic potential for ascent on the eddy lengthscale, which is shown to relate strongly to the frequency of warm conveyor belts (WCBs), dynamic components of extratropical cyclones with large impacts on weather.
by Charles Garrison Gertler.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences
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Baker, Scott Edward. „Power Distribution and Probabilistic Forecasting of Economic Loss and Fatalities due to Hurricanes, Earthquakes, Tornadoes, and Floods in the United States“. Wright State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=wright1462540615.
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Mitchell, Alexandra Lai Ching Kao Andrews. „Hydrous melt generation in the Earth's mantle“. Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104593.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2016.Cataloged from PDF version of thesis. "June 2016."
Includes bibliographical references.
This thesis focuses on quantifying the role of H₂O in the generation and modification of mantle melts at shallow pressures in subduction zones. In the first and second chapters, two experimental studies are presented that investigate direct mantle melting and then subsequent reaction of deeper mantle melts with overlying, cooler depleted mantle. In Chapter 1, the melting behavior of an olivine + orthopyroxene +/- spinel - bearing fertile mantle composition is investigated as a function of variable pressure and water content. The experimental results are used to calibrate a model that can predict the pressure and temperature or the temperature and H₂O content of last equilibration for mantle melts that were in equilibrium with olivine orthopyroxene +/- spinel. In Chapter 2, reaction experiments were conducted to explore the role of melt - rock reaction in the shallow part of the mantle wedge. Results demonstrate the importance of both the temperature of the overlying mantle and the amount of infiltrating melt on the mantle lithology that remains after reaction. Reaction coefficients are calculated to quantify the experimental results. In Chapter 3, H₂O solubility was experimentally determined at upper mantle pressures. The 1.0 GPa result is the first H₂O solubility determination in basalt at any pressure above 0.6 GPa. The final chapter is a modeling study that shows how and when to correct for low pressure fractional crystallization to get lavas back to equilibrium with the mantle. Terms are calibrated (in part, on experiments presented in Chapter 1) that add H₂O to spinel lherzolite multiple saturation point models as well as to thermometers and barometers. The H₂O correction provides the quantitative and qualitative basis for making low pressure fractional crystallization corrections to near-primitive hydrous lavas. All chapters contribute to the understanding of subduction zone magmatism, with a particular emphasis on processes in the shallowest region of the mantle wedge.
by Alexandra Lai Ching Kao Andrews Mitchell.
Ph. D.
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Riese, Martin. „Remote sensing and modeling of the earth's middle atmosphere results of the CRISTA experiment /“. [S.l.] : [s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=964178168.
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50
Stone, Thomas Coleman 1958. „Analysis of the N⁺₂ first negative band system in the Earth's upper atmosphere dayglow“. Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/282770.
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The First Negative (1N) band emission of the molecular nitrogen ion, N⁺₂ , is one of the most prominent features of the terrestrial dayglow spectrum. However, past N⁺₂ studies have encountered problems in validating the intensity of this emission. Also, some anomalous characteristics of the dayglow 1N spectrum remain unexplained, such as a highly developed rotational and vibrational structure. These anomalies appear to be due to the charge exchange reaction: O⁺ + N₂ → N⁺₂ + O, which dominates N⁺₂ ion production at high altitudes. This thesis examines dayglow 1N spectra acquired by the Arizona Airglow Experiment (GLO) flown on the space shuttle mission STS-74. In the analysis the emission is separated into two components. First is the emission from ions produced by photoionization and electron bombardment. Second is emission from ions produced by the charge exchange reaction, which cannot be modeled. The first source is evaluated and subtracted from the observed spectrum. The remaining emission is then used to derive empirical parameters related to the charge exchange reaction. These parameters can be used to estimate the 1N emission rate expected from the thermosphere, based on model atmosphere predictions. This emission rate can be used to determine the dayside O⁺ concentration using the GLO observations.