Дисертації з теми "Précipitations (météorologie) – Régions tropicales"
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Kacimi, Sahra. "Contribution à la restitution des précipitations tropicales par radiométrie micro-ondes : préparation à la mission Megha-Tropiques." Versailles-St Quentin en Yvelines, 2012. http://www.theses.fr/2012VERS0064.
Within the framework of the global warming, the analysis of water and energy budget is of major importance. Considering the Megha-Tropiques (MT) mission whose one of the scientific objectives is to improve the knowledge of water and energy cycle in the intertropical region, the estimation of instantaneous surface rainfall is of the great importance. My PhD work focuses on the optimization of a multi-region, the estimation of instantaneous surface rainfall is of great importance. My PhD work focuses on the optimization of a multi-plateform Bayesian retrieval algorithm called BRAIN (Bayesian Retrieval Algorithm Including Neural Networks) (Viltard et al. , 2006) used for MT. This algorithm uses passive microwave data from satellites such as TRMM, SSM/I and AQUA. It uses a Bayesian Monte Carlo approach to retrieve several atmospheric parameters such as the instantaneous rainfall rate. In order to get a more accurate rainfall restitution, two research axes were investigated : the detection of a priori rainy areas that takes place before the rainfall estimation itself, and the impact of the database and inversion parameters. First, the database on which the algorithm relies needs to be more representative especially as far as high rain rates are concerned. To improve the representativeness of the inversion database, we need first to eliminate repetitive profiles, that is to say extract prototypes from it. To be made, we use Self Organizing Maps SO%s developed by T. Kohonen (2001). Second, the improvement of the rainy-non-rainy pixels classification before the inversion was made using neural networks
Nzeukou, Takougang Armand Cyrille. "Variabilité spatiale à moyenne échelle des conditions de propagation des micro-ondes dans les précipitations." Toulouse 3, 2002. http://www.theses.fr/2002TOU30011.
Saint-Lu, Marion. "Étude des liens entre les événements El Niño et le cycle hydrologique des régions tropicales dans différents contextes climatiques." Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLV028/document.
Interannual variability in the tropical Pacific is mainly modulated by the El Niño / Southern Oscillation (ENSO).Understanding the time evolution of this phenomenon is a major issue, given its strong impacts on health andeconomics. Studying the ENSO variability in different climatic contexts allows us to understand its links to themean-state. We use climatic simulations of the mid-Holocene (6,000 years and 4,000 years before present),the last glacial maximum (21,000 years before present) and a theoretical climate with atmospheric carbondioxyde multiplied by four, computed with several numerical models. We show that ENSO characteristics aresignificantly different in the different climatic contexts. The links between these differences and the climatemean-state are numerous and non linear. Studying paleoclimates is then necessary to understand ENSOchanges and to be able to project its future evolution. Some of the past archives that are used to reconstructthe paleo-ENSO are located in the southwest Pacific, under the influence of the south Pacific convergencezone (SPCZ). We show that the impact of ENSO on the location of the SPCZ changes with the climate.This determines how to interpret archives’ records. Thus, the mechanisms linking ENSO to the SPCZ in themodern climate cannot be directly extrapolated to other climates. By combining information from models andarchives, we are able to improve our understanding on the variability changes in the southwest Pacific. Finally,we address the ENSO change with a new vision, through its role within the global energetic budget. Accordingto the IPSL-CM5A-LR model, the relative contribution of El Niño events to the global energy redistribution isreduced in the mid-Holocene, compared to the modern climate. The mean capacity of the tropical Pacific toexport its energy is reduced. Therefore, the global heat pump represented by the tropical Pacific is less powerfulin the mid-Holocene, both by its reduced capacity to export energy and by the reduced El Niño contribution.This result suggests that there is consistency between the ENSO change and the role of heat pump played bythe tropical Pacific
Garot, Thomas. "Relation Convection-Environnement dans la troposphère tropicale." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLV116/document.
The complexity of the climate depends largely on the water cycle. In the tropics, atmosphericwater is a key parameter, 60% of global rainfall occurs in the tropics. The understandingof the atmospheric water cycle on a global scale need to use satellite observations. The Indo-French satellite Megha-Tropiques, launched in 2011, allows to study for the _rst time simultaneous observations from moisture and rain. The _rst part of the thesis is the study of the impact of a hurricane on its environment. For this, a case study was selected (Typhoon Bopha) and a diagnosis was performed to study the production / consumption of moisture and heat in the typhoon. The second part of the thesis is the study of the relationshipbetween clouds and humidity in the upper troposphere. This study was conducted over the Indian Ocean (between 2011 and 2014) and over the Sahel (between 2012 and 2015)
Guilloteau, Clément. "Approche physico-statistique de la désagrégation des précipitations satellite dans les Tropiques." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30216/document.
Rainfall variability involves a wide range of scales: from the millimeter-scale associated with microphysics to the synoptic scale of the global atmospheric circulation. No existing observation system is able to cover all these scales by itself. Satellite-based observation systems are currently the most efficient systems to resolve the large spatial and temporal scales: from mesoscale meteorology to the synoptic scale. This thesis is dedicated to the exploration of satellites ability to resolve spatial scales from 100km to 2km and temporal scales from 24h to 15 min (in order to resolve the diurnal cycle). The chosen approach is both physical and statistical (or deterministic and probabilistic). The idea is that the deterministic approach can resolve the large scales, but several factors limit its relevance when dealing with fine scales: -The limited resolution of the instruments. -The number of orbiting instruments that limits temporal sampling. -The dynamic nature of fine scale variability. At fines scales, most of the errors in rainfall estimation from satellite comes from not perfectly localizing the precipitating cells. The first objective of this thesis is to identify precisely the lowest limit in scale where the deterministic approach is appropriate. The implementation of the physical-statistical approach relies on an existing multisensor estimate of daily precipitation at a 1° resolution: the TAPEER algorithm developed as part of the Megha-Tropiques mission. The chosen method is a hybrid physical disaggregation and stochastic downscaling via a multiscale representation. The result is an ensemble of high-resolution probable realizations of the rain intensity field. The ensemble is constrained by a high resolution rain detection mask derived from meteosat-SG infrared images at 3km resolution (one image every 15 minutes). The uncertainty associated with the final estimation is handled through the ensemble dispersion. Every realization is generated so that its statistical properties (frequency distribution of the intensities, autocorrelation function) mimic those of the true rain field. The generated fields and the proposed technique contribute to hydrological applications for instance by improving the runoff associated to high precipitation rates in models. Using several realizations is a way to study uncertainty propagation through a model
Duvel, Jean-Philippe. "Climatologie des fluctuations atmospheriques aux courtes echelles de temps : analyse satellitaire des variations diurnes et des modulations quasi-periodiques (3-5 jours) de la convection tropicale sur l'afrique et l'atlantique." Paris 6, 1989. http://www.theses.fr/1989PA066682.
Dieppois, Bastien. "Etude par analyses spectrales de l'instabilité spatio-temporelle des téléconnexions basse-fréquences entre les fluctuations globales du secteur Atlantique et les climats de l'Europe du NW (1700-2010) et du Sahel ouest-africain (1900-2010)." Phd thesis, Université de Rouen, 2013. http://tel.archives-ouvertes.fr/tel-00843683.
Moupfouma, Fidèle. "Etude des précipitations et de leurs effets sur les liaisons hertziennes en visibilité et par satellite dans les régions tropicales." Paris 13, 1987. http://www.theses.fr/1987PA132007.
Fiolleau, Thomas. "Cycle de vie des systèmes convectifs de mousson dans les régions tropicales: préparation à la mission Megha-Tropiques." Phd thesis, Ecole Polytechnique X, 2010. http://pastel.archives-ouvertes.fr/pastel-00576870.
Kebe, Cheikh Mouhamed Fadel. "Relation entre les intégrales spatio-temporelles de la couverture nuageuse et la pluie au sol aux latitudes tropicales : implications pour la mesure des précipitations depuis l'espace." Toulouse 3, 2005. http://www.theses.fr/2005TOU30266.
Chambon, Philippe. "Contribution à l'estimation des précipitations tropicales : préparation aux missions Megha-Tropiques et Global Precipitation Measurement." Phd thesis, Université Paris-Est, 2011. http://pastel.archives-ouvertes.fr/pastel-00664357.
Roucou, Pascal. "Impact des températures de surface océanique d'échelle globale sur la dynamique de l'atmosphère et les précipitations tropicales en Amérique du Sud à l'est des Andes : diagnostic et simulations numériques." Dijon, 1997. http://www.theses.fr/1997DIJOL025.
Oceanic variability is described through the main modes of variability. Time evolution of sea surface temperature (sst) show a warmer south Atlantic and a colder north Atlantic during the 70's and the 80's. This is concomitant of a warming of the pacific and Indian ocean and of stronger El Nino/southern oscillation (enso) episods. Rainfall variability in tropical South America (east of Andes) is described with a new dataset based on 186 stations. Rainfall time evolution, between the 50's and the 70's, is associated with the Atlantic sst gradient but is also modulate by enso. During the recent enso episods rainfall deficits are stronger, particularly in nordeste. Numerical experiments realised with the laboratoire de meteorologie dynamique atmospheric model show that, during an enso and when the atlantic gradient is south/north, subsidence anomalies occur on nordeste and equatorial atlantic. Numerical experiments conduct with the arpege-climat atmospheric model forced with idealised surface conditions show that the atlantic thermic gradient emphasizes a meridian circulation cell on nordeste and atlantic. Anomalies of the sea level pression field are associated with ascending and subsiding anomalies. During the 70's and 80's, subsiding anomalies are reinforced on equatorial atlantic and are linked with more important deficits in nordeste
Guichard, Françoise. "Impact d'un ensemble de nuages sur l'environnement de plus grande échelle vu par un modèle de convection nuageuse explicite (cas GATE et TOGA-GAte)." Toulouse, INPT, 1995. http://www.theses.fr/1995INPT034H.
Oueslati, Boutheina. "Interaction entre convection nuageuse et circulation de grande échelle dans les tropiques." Toulouse 3, 2012. http://thesesups.ups-tlse.fr/1795/.
The spurious double intertropical convergence zone (ITCZ) is a systematic bias affecting state-of-the-art coupled general circulation models (GCM); there is still no consensus on its causes. The goal of this thesis is to shed some light on this outstanding problem toward the improvement of climate model performances. This work emphasizes the roles of coupled ocean-atmosphere and dynamics-thermodynamics feedbacks in the ITCZ structure. The first step was to study the response of the atmospheric GCMs ARPEGE-climat and LMDz in aquaplanet configuration, to a range of SST latitudinal distributions. The purpose was to investigate the existence of multiple precipitation regimes, explore their characteristics and untangle the mechanisms at play in regime transition. The transition from the double regime with two ITCZs to the single regime with only one ITCZ at the equator was analyzed. In both models, the transition between these regimes is mainly driven by changes in the low-level convergence that are forced by the atmospheric boundary layer temperature gradients. Model-dependent, dry and moist feedbacks intervene to reinforce or weaken the effect of the temperature forcing. Dry dynamical feedbacks are mainly driven by horizontal advection of cold subtropical air. Moist thermodynamics which are only active in LMDz; they act as negative feedbacks on low-level convergence and are associated with cooling in the stratospheric cold top and in the boundary layer by convective downdrafts. Moist processes play a crucial role in the ITCZ structure through their influence on the vertical profile of convective heating and modulation of moisture-convection feedbacks, two variables that are very sensitive to the convection scheme and, in particular, to lateral convective entrainment. The influence of lateral convective entrainment on the ITCZ structure is analyzed through a hierarchy of model configurations (coupled ocean-atmosphere, atmospheric and aquaplanet) using the CNRM-CM5 GCM. The sensitivity of the ITCZ structure to this parameter is robust across our hierarchy of models. In response to an increased entrainment rate, the realistic simulations exhibit a weakening of the southern side of the double ITCZ over the southeastern Pacific. The change in ITCZ configuration is associated with a more realistic representation of the tropical circulation driven by feedbacks between large-scale dynamics and deep convection. Together with vertical dynamics, SST and associated coupled feedbacks drive the ITCZ location. Sensitivity experiments to lateral entrainment show that ocean-atmosphere feedbacks amplify the double ITCZ bias. A multi-model analysis using CMIP5 GCMs show that the double ITCZ bias has become small in atmosphere-only simulations, and that coupled atmosphere-ocean feedbacks account for a large part of this bias in coupled simulations
Mourre, Lise. "Précipitations dans les Andes tropicales : analyse spatio-temporelle, intercomparaison de forçages et impacts dans un modèle glacio-hydrologique. Cas du Rio Santa au Pérou." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAU030/document.
Global climate change participates in the redistribution of water resources at the global scale. Impacts are particularly important in mountainous regions where precipitation and temperature gradients are important. In high altitude tropical regions, where precipitation spatial variability is significant, the estimation of precipitation over the broad range of scales of interest for climatologists, meteorologists and hydrologists is challenging. Glacio-hydrological modeling aims at understanding current processes in order to have the ability to give answer on possible evolutions of stream flow that will be caused by climatic changes and the development of anthropogenic activities. The issue of such modeling, in a tropical mountain area, is to reproduce not only the evolution of seasonal flow, but the annual and multi-annual evolution of glaciated areas. However, this type of study is limited by the regionalization of meteorological variables. During the hydrological year 2012/2013, three types of precipitation products (in situ data, satellite data, outputs from a regional climate model (RCM)) are first compared over the Rio Santa watershed in Peru, with an area of 10400 km² which 3.3 % is glaciated, then the impacts of those forcing variables on the outputs of a semi-distributed glacio-hydrological model are evaluated.The satellite product is TRMM 3B42 ; RCM outputs are obtained from WRF at three nested resolutions: 27, 9 and 3 km; daily in situ data are interpolated using a kriging with external drift (KED) algorithm, with the altitude or WRF annual amounts as the external drift. WRF outputs largely overestimate the annual totals, compared to TRMM or KED. However, the physics of the model allows to accurately reproduce the seasonal and daily time cycles of precipitation. TRMM performs poorly over ice covered surfaces and overestimate monthly value during the dry season, making it non representative of precipitation patterns in mountainous areas. Kriging products are good interpolators of precipitation at 3 km resolution. Using altitude as the external drift results in an increase of precipitation to the highest peaks of the Cordillera Blanca; using annual totals of WRF benefits from the atmospheric physic of the model to correctly represent orographic precipitation. Despite a strong overestimation of precipitation quantities, climate modeling provides, for sub-sampled complex topographic area, essential information on the temporal and spatial distribution of precipitation. However, in situ measurements remain essential to estimate precipitation in terms of quantities, and develop interpolation or correction methods of atmospheric model outputs.Glacio-hydrological modeling is performed with the DHSVM-GDM model, including the simulation of glaciated areas and of the glacier dynamic. The strength of such model is to assess the overall element of the water balance, at different time steps. However, it remains difficult to properly represent both the glaciated and non-glaciated areas on a watershed such as the Rio Santa. Using various forcing variables show that a comprehensive study on precipitation is needed before any glacio-hydrological modeling to simulate high altitudes area, impacting the modeling results in terms of ice volume loss
Nuissier, Olivier. "Simulations numériques de cyclones tropicaux à l'aide du modèle Méso-NH." Toulouse 3, 2003. http://www.theses.fr/2003TOU30056.
Atger, Frédéric. "Validation et étude de quelques propriétés de systèmes de prévision météorologique ensemblistes." Toulouse 3, 2003. http://www.theses.fr/2003TOU30051.
Probabilistic meteorological forecasts based on ensemble prediction systems are evaluated. The resolution and reliability components of the decomposition of the Brier score are used for quantifying the performance. Probabilistic forecasts based on operational ensembles are compared to those obtained from a single model run, through a statistical scheme. " Poorman ensembles ", consisting of a few deterministic forecasts run in different operational centres, are evaluated too. The conditions for a realistic estimation of the performance of ensemble based probabilistic forecasts are also investigated. The spatial and interannual variability of the reliability implies a strong stratification of the data, that is not always possible with available samples limited in size. Another, essential issue is the categorization of forecast probabilities, required for achieving the decomposition of the Brier score
Bellenger, Hugo. "Rôle de l'Interaction Océan-Atmosphère dans la Variabilité Intrasaisonnière de la Convection Tropicale." Phd thesis, Ecole Polytechnique X, 2007. http://pastel.archives-ouvertes.fr/pastel-00002325.
Montroty, Rémi. "Impact d'une assimilation de données à méso-échelle sur la prévision cyclonique." Toulouse 3, 2008. http://thesesups.ups-tlse.fr/782/.
Is part of the responsibilities of the RSMC of La Reunion and in line with the research topics of the LaCy and the CNRM-GAME, this PhD thesis has been suggested so as to investigate leads that would help better describe and predict tropical cyclones in a mesoscale model over the Indian ocean. Two main topics were investigated : the use of pseudo-observations of total column water vapour (TCWV) derived from the ECMWF analyses in cloudy/rainy areas jointly with a 3D wind bogus so as to constrain position, size and intensity of tropical cycles, and the use of error variances "of the day" in the data assimilation algorithm. We are interested equally in the position and intensity analyses and forecasts : scores and diagnostics thus target those two quantities. Since tropical cyclones exhibit large circular, cloudy/rainy areas which are devoid of observations that can be assimilated, we look at the impacts of those pseudo-observations of TCWV when assimilated in those areas. It is expected that this data can bring new information to the data assimilation system, thus helping constrain the analysis. The pseudo-observations of TCWV in cloudy/rainy areas are derived from an algorithm built by correlating the ECMWF's 1D-VAR TCWV analyses with the SSM/I brightness temperatures, over the southwest Indian ocean bassin. The TCWV data is then assimilated in a 5-week study during the year 2007, study which covered three intense cyclones over the basin. The TCWV data assimilation is done in 3D-VAR mode in the ALADIN Reunion model and is completed by the use of a 3D wind bogus, developed internally at the CRC. The impacts are very positive in terms of direct position error reduction : at analysis, the error was lowered by 75% and through this better positioning, a positive impact was further seen in the forecasts up to 24h, with statistical significance. The TCWV data impact is most notable in terms of structural improvement : when compared to TMI instantaneous rain rates, the experiment that assimilated both the 3D wind bogus and the TCWV data stands out as reproducing the most realistic cyclonic features. The radius of maximum winds, the pattern of spiral rainbands and the general asymetries of the tropical cyclones are better described thanks to the cycling of this data and are in better agreement with the TMI observations. In order to explore the impact of downscaling from ALADIN Reunion, a version of the high resolution model AROME has been implemented over a part of the southwest Indian ocean and covers Reunion island. The sharper, more realistic orography of the AROME Reunion model at 4 km horizontal resolution allows to better capture cyclonic precipitations. .
Chane-Ming, Fabrice. "Analyse de signaux géophysiques dans l'atmosphère par les techniques en ondelettes : étude des ondes de gravité en région tropicale." Phd thesis, La Réunion, 1998. http://tel.archives-ouvertes.fr/tel-00544533/fr.
Dauhut, Thibaut. "Hector the convector archétype des orages tropicaux hydratant la stratosphère." Thesis, Toulouse 3, 2016. http://www.theses.fr/2016TOU30385/document.
The tropical thunderstorms play an uncertain role in the transport of tropospheric air into the stratosphere, limiting our capability to predict the future climate. The transport by the thunderstorms may be underestimated by the climate models, due to their coarse resolutions. The efficiency of this transport is analysed using numerical simulations of the thunderstorm Hector the Convector with resolutions down to 100 m, the finest ever used for a case of very deep convection. The overshoots, that were observed at its top at 18 km altitude, are captured and the net hydration of the stratosphere is quantified. The contribution of the tropical thunderstorms to the water flux from the troposphere to the stratosphere is then estimated to about 20 %. The almost convergence at 200 m and 100 m suggests that such resolutions are necessary to correctly represent the updafts. The individual analysis of the updrafts indicates that the two tallest contribute beyond 90 % of the mass flux into the stratosphere. They are larger, more vigorous and contain more water than the tallest updrafts one hour before and one hour after, and their convective core was weakly diluted. The supply from the surface by the convergence lines, intensified by the cold pools, and the weak dilution of the two tallest updrafts are determinant for the development of very deep convection. The isentropic analysis of the overturning inside Hector confirms the mass flux computed with the updrafts analysis. It corrects the estimate in the lower troposphere by taking into account the turbulent flux, and in the upper troposphere by filtering out the gravity waves. It highlights the importance of the latent heating due to freezing in the two tallest updrafts during the phase of overshoot in the stratosphere
Henriot, Jean-Michel. "Modélisation du transport d'espèces chimiques en période convective pour l'étude de la haute troposphère tropicale en Amérique du Sud." Phd thesis, Université d'Orléans, 2009. http://tel.archives-ouvertes.fr/tel-00452647.
Tourigny, Étienne. "Analyse de performance d'un modèle régional du climat à simuler la variabilité de la précipitation associée au forçage ENSO dans les tropiques américaines." Mémoire, 2008. http://www.archipel.uqam.ca/1538/1/M10634.pdf.
Tremblay, Lysandre. "Analyse de la variabilité interannuelle de séries temporelles des niveaux d'eau souterraine dans trois régions du Canada." Mémoire, 2009. http://www.archipel.uqam.ca/2587/1/M11159.pdf.