Thesis (Ph. D.)--Rijksuniversiteit te Utrecht, 1946. / Vita. Summary in Dutch. Includes bibliographical references.

Thesis (Doctorgrade)--Universität Hamburg, 1984. / Bibliography: p. 99-100.

Thesis (Ph. D.)--University of Hawaii, 2001. / Includes bibliographical references (leaves 176-184).

Empirical techniques are developed to adjust dynamic model forecasts on the seasonal time scale for southern African summer rainfall. The techniques, called perfect prognosis and model output statistics (MOS), are utilized to statistically "recalibrate" general circulation model (GCM) large-scale fields to three equi-probable rainfall categories for December to February. The recalibration is applied to a GCM experiment where simultaneously observed sea-surface temperature (SST) fields serve as the lower boundary forcing, referred to as the simulation mode experiment. Cross-validation sensitivity tests are first performed over a 28-year climate period to design an optimal canonical correlation analysis (CCA) model for each of the two recalibration methods. After considering several potential predictor fields, the 700 hPa geopotential height field is selected as the single predictor field in the two sets of statistical equations that are subsequently used to produce recalibrated rainfall simulations over a 1 a-year independent test period. Patterns analysis of the predictor and predictand fields suggests that anomalously low (high) 700 hPa geopotential heights over the subcontinent are associated with wet (dry) conditions over land, an association that is supported by observational evidence of rain (drought) producing systems. Additionally, the dominant mode of the recalibration equations is associated with the EI Nino/Southern Oscillation (ENSO) phenomenon. Somewhat higher retro-active skill levels are found using the MOS technique, but the computationally less intensive perfect prognosis technique should also be able to produce usable seasonal rainfall forecasts over southern Africa in an operational forecast environment hampered by the lack of computing resources. / Dissertation (MSc)--University of Pretoria, 2006. / Geography, Geoinformatics and Meteorology / Unrestricted

The Antarctic sea ice region is relatively stable in extent from year to year and sees little long-term variability, the primary driver for its seasonal advance and retreat being the seasonal changes in advection of heat through the atmosphere. However, observations show a slight positive trend in its extent over recent decades. Recent work has built on the hypothesis that anomalous poleward moisture fluxes could be seen in concert with anomalous decreases in sea ice variability by providing evidence of this correlation in the Arctic sea ice region. In order to test this hypothesis and to investigate the atmospheric circulation patterns during states of low sea ice concentration in the Antarctic, records of de-seasonalized sea ice concentration anomalies are made for five regions of the Antarctic polar region, and composite distributions of variables of atmospheric circulation for the lowest 10th percentile of months with low mean sea ice concentration are compiled. Meridional moisture fluxes from these composites are tested against the entire population of meridional moisture fluxes using the Student's t-test with a confidence level of 95%, and the differences from the overall mean fields for atmospheric conditions during these cases are calculated. Of the five regions, the Ross Sea, Weddell Sea, and Pacific Ocean sections exhibit significant local moisture flux anomalies in the direction of the pole during months with low sea ice concentration, supporting the hypothesis that moisture transport into the polar region is important for the variability of sea ice in the Antarctic. The Bellingshausen - Amundsen Seas and Indian Ocean sectors show weak local signals of poleward moisture fluxes, indicating that there are other varying factors affecting the sea ice more heavily in these regions. Mean geopotential height anomalies during months with anomalously low sea ice concentration indicate that the Weddell Sea and Pacific Ocean regions are coupled with the positive phase of the Southern Annular Mode, while low sea ice concentration in the Indian Ocean as well as the Bellingshausen and Amundsen Seas regions show concurrence with the negative phase. With general circulation models predicting a persistence of the positive phase of the Southern Annular Mode in a warming climate, it is important to understand how the Antarctic sea ice region responds to the phase of this oscillation.

Ce travail est l'expression d'une volonté de chercheurs, de la Carabe d'améliorer les connaissances scientifiques méso- et micro-météorologiques appliquées aux milieux insulaires sous influence des alizés et de développer la recherche dans ces domaines.On sait que le phénomène météorologique le plus remarquable impactant les îles de la Caraïbe reste le cyclone tropical. Mais d'autres phénomènes, a des échelles inferieures, telles que les pluies intenses, les houles, la dégradation de la qualité de l'air ont une importance aigüe en termes de risques naturels ou de risques sur la sante. Ces exemples attestent la nécessité d'utiliser des méthodes de descente d'échelle pour exploiter l'information météorologique et/ou climatique de grande échelle et dériver des scenarios locaux et régionaux appliques aux territoires insulaires. Ce défi est important car l'attente d'analyses scientifiques pertinentes dans ces domaines est grande.Les travaux présentés dans ce mémoire ont pour principaux objectifs la simulation numérique puis l'analyse des mécanismes méso- et micro-échelles qui induisent des circulations locales diurnes et nocturnes sur l'archipel de la Guadeloupe à l'aide de codes numériques météorologiques éprouves car largement utilises en recherche et en prévision opérationnelle.Ils constituent donc la première étude de modélisation numérique à haute résolution en basse atmosphère, par descente d'échelle dynamique, pour des intervalles d'espace compris entre 1 km et 111 m sur cet archipel.Le modelé atmosphérique Weather Research and Forecasting ARW V3.4 (WRF ARW), non-hydrostatique, a été utilise pour l'ensemble des simulations pour modéliser la troposphère depuis l'échelle globale à l'échelle de la turbulence.Trois situations météorologiques classiques réelles d'une durée de 48 heures, correspondant à 80 % des situations météorologiques observées dans la zone, alizes soutenus (AS), alizes moyens (AM), alizes faibles (AF) ont été examinées. Ces situations sont caractérisées par les valeurs du nombre de Froude local suivantes : 0,82 (AS), 0,41 (AM) et 0,21 (AF). Six domaines de modélisation ont été sélectionnés pour effectuer les descentes d'échelle dynamiques : D01 (maille de 27 km), D02 (maille de 9 km), D03 (maille de 3 km), D04 (maille de 1 km), D05 (maille de 333 m) et D06 (maille de 111 m) avec soixante-dix niveaux verticaux. Les quatre premiers domaines (D01 à D04) couvrent l'archipel de la Guadeloupe et sont utilisés en mode méso-échelle à l'aide d'un schéma d'ensemble de couche limite planétaire YSU. Les domaines D05 (couvrant l'île de la Basse-Terre et le centre de l'archipel) et D06 (couvrant la zone littorale et rurale du Petit Cul-de-Sac Marin et la zone urbaine de l'agglomération pointoise) sont utilisés en mode Large Eddy Simulation avec une fermeture de la turbulence 1,5 TKE 3D. Le modèle WRF a été forcé toutes les six heures par l'assimilation des champs d'analyses globales du modèle NCEP FNL (1° de résolution). Les simulations effectuées ont permis d'obtenir des champs de variables météorologiques 10-minutes à très hautes résolutions spatiales.Les résultats des simulations méso- et micro-échelles ont été confrontés aux valeurs expérimentales obtenues à l'aide de capteurs places sur des mâts météorologiques (campagne Atmo-Mangrov et réseau de mesure Météo-France). Il s'agissait d'optimiser l'utilisation des couplages de codes numériques tout en conservant la possibilité de les confronter aux observations expérimentales.Les résultats des simulations numériques micro-échelles, des différents cas (AS, AM, AF) sont utilisées pour forcer (c'est-à-dire définir les conditions limites) un modèle lagrangien de dispersion de particules : FLEXPART. Le système couple FLEXPART-WRF a été employé dans le domaine D06 pour étudier la dispersion du panache d'oxydes d'azote émis par la principale usine de production d'électricité de l'île. / The present work expresses the will of Caribbean researchers to improve the meso- and micro-meteorological scientific knowledge of the trade winds influenced island areas, and to develop research in these domains.It is well known that tropical hurricanes remain the most remarkable meteorological phenomena that affect the Caribbean islands. But some other phenomena, of smaller scale, such as intense rainfall events, swells, or air quality degradation, are of extreme importance for natural or health hazards. These examples show the need to use downscaling methods to exploit large scale meteorological or climatic information, and to obtain local and regional scenarios for the island areas. This is an important challenge, as sound scientific studies in these matters are eagerly expected. The aim of the research works exposed in the present dissertation is numerical simulation and analysis of the meso- and microscale mechanisms that induce diurnal and nocturnal local circulations in the Guadeloupe archipelago, using numerical meteorological models that are widely used in research and in operational forecasting.These works represent the first high-resolution (1 km to 111 m) numerical study of the lower atmosphere over the Guadeloupe archipelago. The Weather Research and Forecasting ARW 3.4 (WRF-ARW) model is used to simulate the troposphere from global scale to turbulence scale. Real cases of three typical weather types (80% of cases during a year) are examined during 48 hours : strong trade winds (STW), medium trade winds (MTW) and weak trade winds (WTW). These weather types are characterized by values of the local Froude number : 0.82 (STW), 0.41 (MTW) and 0.21 (WTW). Six domains have been selected for the dynamical downscaling : D01 (grid spacing of 27 km), D02 (grid spacing of 9 km), D03 (grid spacing of 3 km), D04 (grid spacing of 1 km), D05 (grid spacing of 333 m) and D06 (grid spacing of 111 m), including 70 vertical levels. The first four domains (D01 to D04) cover the Guadeloupe archipelago and are used in the meso-scale simulations with the planetary boundary layer scheme YSU (ensemble mean). Domain D05 (covering the Basse-Terre island and the middle of the archipelago) and domain D06 (covering the coastal and rural area of Le Petit Cul-de-Sac Marin and the urban area of Pointe-à-Pitre), are employed in the micro-scale simulation (LES) with the 3D TKE 1.5 order closure scheme. WRF has been 6 hourly reinitialized with the NCEP FNL global analyses (resolution of 1°). These simulations permitted to obtain 10-minutes meteorological variable fields with a very high resolution (111 m).Meso-scale and micro-scale model results have been evaluated with observational data from meteorological stations (field campaign Atmo-Mangrov, French Met Office).Once validated, the micro-scale model outputs have been used for the assimilation of the lagrangian particle dispersion model : FLEXPART. The coupling FLEXPART-WRF has been employed in domain D06, in order to analyze the dispersion of the nitrogen oxide plume emitted by the main power plant of the archipelago.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Meteorology and Physical Oceanography, 1981. / Microfiche copy available in Archives and Science. / Vita. / Bibliography: leaves 193-200. / by Lee Edward Branscome. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Meteorology and Physical Oceanography, 1982. / Microfiche copy available in Archives and Science. / Bibliography: leaves 75-77. / by John Roberts Anderson. / M.S.

Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Meteorology, 1979. / Microfiche copy available in Archives and Science. / Vita. / Bibliography: leaves 242-247. / by Antony Brett Mullan. / Sc.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Meteorology, 1980. / Microfiche copy available in Archives and Science. / Bibliography: leaves 44-46. / by Till E. Stoeckenius. / M.S.