Дисертації з теми "Impact sur le climat"
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Fluteau, Frédéric. "Impact de la tectonique des plaques sur le climat." Paris 7, 1999. http://www.theses.fr/1999PA077090.
Dessert, Céline. "Impact du volcanisme sur le climat et sur les cycles géochimiques globaux." Toulouse 3, 2002. http://www.theses.fr/2002TOU30204.
Déandreis, Céline. "Impact des aérosols anthropiques sur le climat présent et futur." Paris 6, 2008. http://www.theses.fr/2008PA066139.
Ardilouze, Constantin. "Impact de l'humidité du sol sur la prévisibilité du climat estival aux moyennes latitudes." Thesis, Toulouse, INPT, 2019. http://www.theses.fr/2019INPT0048/document.
Severe heat waves and droughts that episodically hit temperate regions have detrimental consequences on health, economy and society. The design and deployment of efficient preparedness strategies foster high expectations for the prediction of such events a few weeks or months ahead. Their likely increased frequency throughout the 21st century, as envisaged by climate projections, further emphasizes these expectations. Nevertheless, the summer season is the most difficult to predict over mid-latitudes. Well-known sources of predictability are weaker than in winter and current climate prediction systems struggle to adequately represent associated teleconnection mechanisms. An increasing number of studies have shown a statistical link over some regions between spring soil moisture and subsequent summer temperature and precipitation. This link has been partly confirmed in climate numerical models, but many questions remain. The purpose of this PhD thesis is to better understand the role played by soil moisture onthe characteristics and predictability of the summer climate in temperate regions. By means of the CNRM-CM coupled general circulation model, we have designed a range of numerical simulations which help us evaluate the persistence level of spring soil moisture anomalies. Indeed, a long persistence is a necessary condition for these anomalies to influence the climate at the seasonal scale, through the process of evapotranspiration. By imposing in our model idealized initial and boundary soil moisture conditions, we have highlighted areas of the globe for which the average state and the variability of temperatures and precipitation in summer is particularly sensitive to these conditions. This is the case in particular for Europe and North America, including over high latitudes. Soil moisture is therefore a promising source of potential seasonal climate predictability for these regions, although the persistence of soil moisture anomalies remains locally very uncertain. An effective predictability coordinated experiment, bringing together several prediction systems, shows that a realistic soil moisture initialization improves the forecast skill of summer temperatures mainly over southeast Europe. In other regions, such as Northern Europe, the disagreement between models comes from uncertainty about the persistence of soil moisture anomalies. On the other hand, over the American Great Plains, even the forecasts with improved soil moisture initialization remain unsuccessful. Yet, the literature as well as our assessment of climate sensitivity to soil moisture have identified this region as a "hotspot" of soil moisture - atmosphere coupling. We assume that the failure of these predictions relates to the strong hot and dry bias present in all models over this region in summer, which leads to excessive soil drying. To verify this assumption, we developed a method that corrects these biases during the forecast integration based on the CNRM-CM6 model. The resulting forecasts are significantly improved over the Great Plains. Understanding the origin of continental biases in the summer and reducing them in future generations of climate models are essential steps to making the most of soil moisture as a source of seasonal predictability in temperate regions
Armandine, Les Landes Antoine. "Impact des variations climatiques sur les ressources hydrogéologiques." Thesis, Rennes 1, 2014. http://www.theses.fr/2014REN1S101/document.
Groundwater resources represent approximately 98% of global freshwater resources available for humans on our planet; therefore groundwater is fundamental resource of our societies. Due to climate change and strong link between climate and the cycle of water, an understandable concern is appeared about the potential impacts of climate change on water resources. Nowadays, growing body of evidence supports the fact that changes in climatic conditions (temperature, precipitation, evaporation…) impact the hydrologic cycle and consequently groundwater resources. The identification of groundwater sensibility to climate variations has become essential. The climate is a highly complex system where its variations drive by many factors both natural and human occurs on all time scales. Climatic changes are not a new phenomenon, groundwater resources have already been impacted by effects of climatic variations, are impacting presently and will be in the future. The work carried out under this thesis covered this problematic to characterize the groundwater resources sensibility to climate variations. With the help of environmental tracers analyzed at the regional scale, impacts of major climate events occurred since the last millions years (marine transgression and glacial period) have been identified in the current hydrogeologic system. Then, support by hydrogeological modeling the impact of climate change has been studied through the specific relationships between groundwater and surface water bodies and ocean. All these studies highlight the important sensibility of groundwater resources to climate variations in terms of quality (salinization) and quantity (lower water levels). Hydrogeological resources are particularly sensitive to climate and hydrological variations (recharge changes, seawater intrusion…), as well as to non-climatic factors (human activities). Thus groundwater resources management needs to consider both climatic and non-climatic risks and the long-term adaptation of these systems
Deroubaix, Adrien. "Impact des aérosols désertiques et du climat sur les épidémies de méningites au Sahel." Paris 6, 2013. http://www.theses.fr/2013PA066464.
Meningitis epidemics are a major public health problem in several African countries belonging to the “meningitis belt”. The dry season in the Sahel lasts from November to May, when the Harmattan wind, coming from the Sahara, carries dust at the ground level into this region. The period of maximum meningitis incidence (i. E. The ratio of the number of meningitis cases and the respective population) coincides with the period of highest temperatures and dust concentrations in the Sahel. A database with weekly epidemiological and geophysical parameters has been created at different spatial scales (district, region, national) based on four ERA-interim variables (temperature, humidity, wind force and wind angle) and the Aerosol Index (AI). However in a first step, the AI has been compared to dust concentration measurements at the ground level and thus been validated in the context of dust impact studies on health. At the national scale, a time-lag of several weeks has been showed between the increase of the aerosol optical thickness and the meningitis incidence. This time-lag was also found using the AI at the national scale and at the district scale. During the epidemic years, a statistical model of the weekly meningitis incidence has been established based on temperature and ground dust concentration. This model explains 1/3 of the variance of meningitis incidence observed. Moreover, the onset dates of the outbreaks are well retrieved at the country scale (R = 0. 94). These results show that climate and Saharan dust must be taking into account to explain the seasonality of meningitis epidemics
Dahech, Salem. "Le vent à Sfax (Tunisie) : impact sur le climat et la pollution atmosphérique." Paris 7, 2007. http://www.theses.fr/2007PA070002.
This work aims to studying wind and weather types including their effects on meteorological parameters and atmospheric pollutants space distribution in Sfax agglomeration. At first, wind and weather types are determined using three-hourly meteorological data. Sunny days are the most frequent; they are related to NO wind in winter and to sea breeze or sirocco during the other seasons. The characteristics of these tow last winds are detailed on the basis of data recorded by National Institute of Meteorology and private automatic weather stations. At second, temperature, humidity and sea breeze space distribution is analyzed on the scales of the agglomeration, the quarter and the street by fixed and itinerant measurement as well as NOAA-AVHRF data. Weather types, building areas density and geometry, streets orientation and depth are the main factors explaining the space distribution of weather variables indicated above. The peaks of pollution (CO, SO2 and NOX) recorded in the downtown area by the National Agency of the Environmental Protection station are observed between 20h and midnight, during the sea breeze days at the nocturnal shift. CO measurements by portable sensors as well as the numerical modelling of the SO2 rates show the impact of wind speed and direction, boundary layer height, emission sources (road traffic, SIAPE and dumpsite) and urban morphology on the air quality. By means of Geographical Information System, the area affected by SO2 rates exceeding WHO recommendation is defined
Chaboureau, Anne-Claire. "Impact du climat et de la tectonique sur la dynamique des systèmes sédimentaires pendant l'ouverture de l'Atlantique Sud." Phd thesis, Université Rennes 1, 2012. http://tel.archives-ouvertes.fr/tel-00830475.
Demory, David. "Impact de la température sur le phytoplancton et ses interactions avec les virus." Electronic Thesis or Diss., Paris 6, 2017. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2017PA066167.pdf.
Climate changes induced by human activities will deeply impact natural ecosystems. Marine ecosystems, leaving in a highly variable environment, are therefore threatened. Within these communities, phytoplankton have a primordial role in the trophic web and in the regulation of climate processes. Understanding the evolution of these communities in a warming world is an issue of oceanography. Among factor affecting phytoplankton dynamics, viruses play a key role through their capacity to lyse their hosts. They are therefore controlling the phytoplankton population dynamics. It is then crucial to understand how the viruses impact will evolve in a warming ocean. In this thesis we explore the impact of temperature on these interactions with an integrative method combining laboratory experiments and mathematical modelling. We focus on the pico-eukaryote genus Micromonas. In a first study, we have characterized the temperature response of the Micromonas genus by studying 11 different strains. We have shown the primordial role of temperature on the ecology of phytoplankton. In particular, we have demonstrated that ocean temperature has played a decisive role in evolution. Thus, we have been able to predict the evolution of biodiversity in a warming ocean. In a second study we showed that temperature is a key factor in controlling the phytoplankton - virus dynamics. The temperature affects in particular the rates of infectivity loss and of virus degradation, as well as the rate of virus production. In particular, we observed a change in infection strategy. Beyond a temperature close to the optimal growth temperature, the dynamics become more complex suggesting a change in infection strategy from lytic to chronic. In a third study, we have developed a mathematical model representing these interactions. The model efficiently reproduced the observed changes as a function of temperature. Finally, we discuss the role of temperature on the involved infection processes
Azuara, Julien. "L'influence du climat et des activités humaines sur l'histoire holocène de la végétation du nord-ouest de la Méditerranée." Thesis, Paris, Muséum national d'histoire naturelle, 2017. http://www.theses.fr/2017MNHN0012/document.
Holocene climate fluctuations and human activities since the Neolithic have shaped present-day Mediterranean environments. Separating anthropogenic effects from climatic impacts to better understand Mediterranean paleoenvironmental changes over the last several millennia remains a challenging issue. This work aims to characterize the influence of human activities and past climate variability over the development of north western Mediterranean environments by (i) providing new data about the vegetation history of this region and (ii) developing new tools for paleoenvironmental data processing. Two high-resolution pollen sequences from Languedoc (France) and the Murcia region (Spain) are presented, covering the last 7800 and 6500 years, respectively. In Languedoc, the past vegetation is dominated by mesophilous forests during most of the sequence, in particular beech forests growing at low altitude within the Mediterranean area. However, recurrent abrupt climate changes, the late Holocene aridity trend, and human deforestation caused beech forests to decline. On the other hand, evergreen Mediterranean vegetation has developed gradually since the Neolithic due to the increasing human impact. In the Murcia region, the influence of past climate variability on the environment is less obvious. Changes in human activities are clearly driving most of the observed vegetation changes. Shrubs and pioneer plants show spread and decline phases alternatively in relation to archeological and historical records. Work to adapt pollen based land-cover reconstruction methods developed in northern Europe to the Mediterranean area was also initiated. REVEALS model of pollen dispersal and deposition was adapted to coastal sedimentary basins such as those studied in this PhD. However, to apply such pollen based land-cover reconstruction methods, pollen productivity estimates are needed. Thus, the data necessary to quantify the pollen productivity of 12 Mediterranean plant taxa were collected and processed. Finally, spectral analysis of paleoclimate time series using wavelets allowed us to characterize the influence of solar variability, the Atlantic thermohaline circulation, and tropical climate variability on the past climate of the north-western Mediterranean. The spatial variability of past climate changes in the Mediterranean is also highlighted by comparing our results obtained for the north western Mediterranean with paleoclimate data from the whole Mediterranean basin
Delebecq, Gaspard. "Impact des facteurs hydroclimatiques sur la production primaire des macroalgues." Thesis, Lille 1, 2011. http://www.theses.fr/2011LIL10186.
The aim of this thesis was to study the photosynthetic performances of different populations of Laminaria digitata along the French coast and their ability to cope with the variations of light and temperature. Three populations located in the North of France and in the North and South Brittany were studied in situ during spring tides (with the set up of an automated benthic chamber which measure the photosynthetic activity during immersion) and in the laboratory. Results highlight the spatial and temporal heterogeneity in the photosynthetic response of L. digitata along its distributional range on the French coast. The photosynthetic activity of L. digitata is highly dependent on the daily and seasonal variations of irradiance. The high irradiances experienced by the sporophytes of L. digitata during low spring tides can lead to the photoinhibition of the photosystem II which was shown to rely on the set up of the photoprotective mechanisms. Photoprotection implies the activation of the xanthophyll cycle which was also described for the first time in the gametophyte of L. digitata. Between the different populations, the heterogeneity in the photosynthetic response of L. digitata is related to the local light and temperature conditions which may result in different ecotype along the French coast. Finally, photosynthetic performances of L. digitata were compared with those of the opportunistic specie Saccorhiza polyschides which is probably competing with L. digitata in Brittany
Sy, Souleymane. "Impact du changement d'occupation des sols passé et à venir sur la dynamique de la circulation de la mousson ouest africaine." Electronic Thesis or Diss., Paris 6, 2016. https://accesdistant.sorbonne-universite.fr/login?url=https://theses-intra.sorbonne-universite.fr/2016PA066208.pdf.
By climate models developed in the LUCID project and CMIP5 models used in the LUCID-CMIP5 projet, this thesis aims to identify and evaluate biogeophysical impacts of LULCC of the past 150 years and the end of XXIst century on surface climate in West Africa. Focusing analysis in two contrasted regions of West Africa: Sahel and Guinea where land cover change is above 5% since pre-industrial times, results reveal expansion of crops and pasture and deforestation in Guinea in all LUCID models. In this work, simulations of present-day rainfall and surface air temperature have been compared with observed datasets. Results show that the observed mean and inter-annual variability of rainfall are respectively underestimated and overestimated by most of the seven climate models. Overall surface air temperature is better simulated than precipitation.Two simulations of rainfall and surface air temperature, forced respectively with present-day and pre-industrial land cover distribution are also compared. Results show that there is no obvious/visible difference between the two simulations with respect to mean climatic values of both rainfall and temperature as if the changes in land cover did not really matter for the good representation of those variables. Finally, this thesis evaluates leaf area index (LAI) in the LUCID models and its relationships with surface climate. Observations reveal that precipitation is highly and positively correlated to foliage density with values larger or equal to 0.8 in both the Sahel and Guinea. Five out of seven models show positive correlations, but not as large as in the observations. However none of the models is able to capture a larger correlation between precipitation and LAI in Guinea than in the Sahel. Most of climate models show that correlation between LAI and surface air temperature is positive in the Sahel and negative in Guinea. It suggests that more LAI in Guinea will lead to more evapotranspiration and therefore cooler surface, while in the Sahel the albedo effect of increased LAI may dominate and increase surface temperature. Finally, analysis reveals that historical effects of land-use changes are not regionally significant among the seven climate models due to a small land-cover change prescribed in these regions compared to the changes induced by large scale forcing such as sea surface temperatures changes and CO2 concentration increase.Furthermore, biogeophysical impact of land-use change in the XXIst Century climate were evaluated using specific simulations similar to RCP8.5 scenarios but with a prescribed fixed land cover map on 2006. The analysis reveals, that in contrast of last 150 years, deforestation continues in the coming years in tropical region in scenarios resulting from the extension of the cultivated area reaching 15 million km2 in 2100 over tropical Africa. Regionally, the biogeophysical impacts of projected changes in land cover in RCP8.5 scenarios were generally small but statistically significant in the Sahel and Central Africa regions where deforestation is more than 10% with a wide dispersion of climate response due to differents parameterizations of land surface in climate models
Vischel, Théophile. "Impact de la variabilité pluviométrique de méso-échelle sur la réponse des systèmes hydrologiques sahéliens : modélisation, simulation et désagrégation." Grenoble INPG, 2006. http://www.theses.fr/2006INPG0033.
It is of primary importance to understand how the climate variability influences the response of the Sahelian hydrological systems in ord to anticipate the hydrological impact of future climate changes and to define suitable strategies. Such studies require linking the large scale climate scenarios to the very localized water budget of sm ail catchments. This work deals with such scale issues which are essential when outputs of climate models are used to force hydrological models. The data used here characterize the continuum of space-time scales displayed by the Iwo types of hydrological systems of the Sahelian region: the sm ail endoreic systems at the left bank of the Niger River and the larger right bank tributary exoreic systems. Three main axes are investigated in the work. First we synthesize and update previous works about the description and the modelling of mesoscale rainfall variability, through the fine scale data from the AMMA-CATCH Niger observa tory. Then the impact of the spatial and temporal rainfall variability on runoff is quantified by assessing the error committed when input hydrological model data used sub-sample this rainfall variability. Finally, regarding these results and by using the developed modelling tools, rainfall regime changes and their impact on runoff are investigated through (i) the characterization of changes that have occurred during the particularly dry 1970-1989 period, (ii) hypothetic scenarios based on the actual knowledge of the potential climate changes that cou Id occur in the future
Séférian, Roland. "Impact du changement climatique sur les flux de carbone océaniques : rôle de la variabilité décennale." Versailles-St Quentin en Yvelines, 2013. http://www.theses.fr/2013VERS0057.
Since the industrial revolution, oceans have absorbed roughly one quarter of the anthropogenic emissions of CO2, slowing down climate change. The evolution of the ocean carbon sink, paralleled to the anthropogenic CO2 emissions, is ruled by the CO2 as well as climate. Influence of atmospheric CO2 in the recent evolution of the ocean carbon sink is well understood whilst this is not the case for the climate’s one. Indeed, some authors claim that the recent variations of the ocean CO2 sink can be attributed to climate change, whereas some others suggest that these latter are controlled by a decadal variability, which is poorly understood. In this thesis, we address question relative to the role of the decadal variability of the ocean carbon fluxes through the mean of numerical modeling. On one hand, we have demonstrated that ocean carbon fluxes exhibit decadal fluctuations within the high latitudes oceans. These fluctuations displays modes of 10 to 50-year long which account for 20–40% of the year-to-year variability. Thanks to Detection & Attribution methods applied to RECCAP project’s reconstructions (1960–2005), we have then assessed whether the occurrence of fluctuations at decadal time scale could hamper the detection of the climate contribution to the recent evolution of ocean carbon fluxes. We have shown that the climate contribution is indeed not detected in the high latitude oceans due to the presence of decadal mode of variability. In the low latitude oceans instead, the weaker fluctuations of ocean carbon fluxes at decadal time scale favor the detection of climate influence in the recent variations of the CO2 fluxes
Bossay, Sébastien. "Impact de la variabilité solaire sur l’ozone de la moyenne atmosphère." Thesis, Versailles-St Quentin en Yvelines, 2015. http://www.theses.fr/2015VERS002V/document.
A large part of the natural variability of the atmosphere and climate is related to solar variability. One of the forcing mechanisms of solar variability is based on perturbations of the middle atmosphere (stratosphere, mesosphere), particularly through ozone variations (photochemical processes), that then propagate through the troposphere to the surface. The thesis focuses on the first stage of this forcing mechanism, i.e. perturbations of ozone associated with solar variability and more specifically at the 27-day solar rotational time scales. The relationship between ozone and solar variability is studied not only using several time series of satellite data (MLS and GOMOS) but also results of a chemistry-climate model (LMDz-Reprobus) over analysis windows varying from 1 to 15 years. The mean ozone sensitivity to the 27-day solar cycle (% of ozone variation for 1% change in solar forcing) is characterized by positive values from 10 to 1 hPa with a maximum of 0.4 at 3 hPa. This sensitivity varies strongly depending on the size of the analysis window indicating that the solar signal can be masked by the dynamical variability, even during periods of strong solar activity. The dispersion of the results is found to be anti-correlated with the amplitude of the solar rotational fluctuations that are related to the phase of the 11-year solar cycle. In the mesosphere, ozone is found to be anti-correlated with solar variability with a maximum around 80 km. This corresponds exactly to the altitude of the maximum in the solar-induced enhancement of OH, the dominant radical in the destruction of mesospheric ozone
Demory, David. "Impact de la température sur le phytoplancton et ses interactions avec les virus." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066167/document.
Climate changes induced by human activities will deeply impact natural ecosystems. Marine ecosystems, leaving in a highly variable environment, are therefore threatened. Within these communities, phytoplankton have a primordial role in the trophic web and in the regulation of climate processes. Understanding the evolution of these communities in a warming world is an issue of oceanography. Among factor affecting phytoplankton dynamics, viruses play a key role through their capacity to lyse their hosts. They are therefore controlling the phytoplankton population dynamics. It is then crucial to understand how the viruses impact will evolve in a warming ocean. In this thesis we explore the impact of temperature on these interactions with an integrative method combining laboratory experiments and mathematical modelling. We focus on the pico-eukaryote genus Micromonas. In a first study, we have characterized the temperature response of the Micromonas genus by studying 11 different strains. We have shown the primordial role of temperature on the ecology of phytoplankton. In particular, we have demonstrated that ocean temperature has played a decisive role in evolution. Thus, we have been able to predict the evolution of biodiversity in a warming ocean. In a second study we showed that temperature is a key factor in controlling the phytoplankton - virus dynamics. The temperature affects in particular the rates of infectivity loss and of virus degradation, as well as the rate of virus production. In particular, we observed a change in infection strategy. Beyond a temperature close to the optimal growth temperature, the dynamics become more complex suggesting a change in infection strategy from lytic to chronic. In a third study, we have developed a mathematical model representing these interactions. The model efficiently reproduced the observed changes as a function of temperature. Finally, we discuss the role of temperature on the involved infection processes
Fane, Moussa. "Impact du climat sur l'écologie et la transmission du paludisme : analyse du risque palustre dans le septentrion malien." Thesis, Grenoble, 2011. http://www.theses.fr/2011GRENS042/document.
Nous pensons que ces résultats aideront les acteurs de santé publique à mieux comprendre l’épidémiologie du paludisme au Sahel, en vue d’orienter d’avantage la recherche sur des outils additionnels de lutte pour freiner la propagation du paludisme grâce à la gestion environnementale. Ils fournissent une piste prédictive du comment le changement climatique impactera la transmission du paludisme en Afrique
Sy, Souleymane. "Impact du changement d'occupation des sols passé et à venir sur la dynamique de la circulation de la mousson ouest africaine." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066208/document.
By climate models developed in the LUCID project and CMIP5 models used in the LUCID-CMIP5 projet, this thesis aims to identify and evaluate biogeophysical impacts of LULCC of the past 150 years and the end of XXIst century on surface climate in West Africa. Focusing analysis in two contrasted regions of West Africa: Sahel and Guinea where land cover change is above 5% since pre-industrial times, results reveal expansion of crops and pasture and deforestation in Guinea in all LUCID models. In this work, simulations of present-day rainfall and surface air temperature have been compared with observed datasets. Results show that the observed mean and inter-annual variability of rainfall are respectively underestimated and overestimated by most of the seven climate models. Overall surface air temperature is better simulated than precipitation.Two simulations of rainfall and surface air temperature, forced respectively with present-day and pre-industrial land cover distribution are also compared. Results show that there is no obvious/visible difference between the two simulations with respect to mean climatic values of both rainfall and temperature as if the changes in land cover did not really matter for the good representation of those variables. Finally, this thesis evaluates leaf area index (LAI) in the LUCID models and its relationships with surface climate. Observations reveal that precipitation is highly and positively correlated to foliage density with values larger or equal to 0.8 in both the Sahel and Guinea. Five out of seven models show positive correlations, but not as large as in the observations. However none of the models is able to capture a larger correlation between precipitation and LAI in Guinea than in the Sahel. Most of climate models show that correlation between LAI and surface air temperature is positive in the Sahel and negative in Guinea. It suggests that more LAI in Guinea will lead to more evapotranspiration and therefore cooler surface, while in the Sahel the albedo effect of increased LAI may dominate and increase surface temperature. Finally, analysis reveals that historical effects of land-use changes are not regionally significant among the seven climate models due to a small land-cover change prescribed in these regions compared to the changes induced by large scale forcing such as sea surface temperatures changes and CO2 concentration increase.Furthermore, biogeophysical impact of land-use change in the XXIst Century climate were evaluated using specific simulations similar to RCP8.5 scenarios but with a prescribed fixed land cover map on 2006. The analysis reveals, that in contrast of last 150 years, deforestation continues in the coming years in tropical region in scenarios resulting from the extension of the cultivated area reaching 15 million km2 in 2100 over tropical Africa. Regionally, the biogeophysical impacts of projected changes in land cover in RCP8.5 scenarios were generally small but statistically significant in the Sahel and Central Africa regions where deforestation is more than 10% with a wide dispersion of climate response due to differents parameterizations of land surface in climate models
Boisier, Juan Pablo. "Évaluer les impacts robustes du changement d'usage des sols sur le climat des 150 dernières années et sur le climat projeté pour le siècle prochain." Phd thesis, Palaiseau, Ecole polytechnique, 2012. https://pastel.hal.science/docs/00/78/79/72/PDF/Manuscrit_final_these_Boisier.pdf.
Land-use change (LUC) is an important climate forcing due to the underlying alterations of the properties of the soil-vegetation system. However, the knowledge of these biogeophysical impacts of LUC is middling, notably due to the large number of processes involved. By means of model intercomparison and other approaches specifically developed, this study aims to identify the robust climate signals of LUC as well as to assess the associated uncertainties. LUC since the preindustrial period has led to extensive deforestation in the northern temperate regions and therefore to increases in surface albedo. The amplitude of this impact and the role of the non-radiative effects in summer are still quite uncertain within the model results. These uncertainties respond (1) to the way LUC is implemented in land surface models (LSMs) and (2) to the intrinsic model sensitivities to LUC. We show that the second point could explain more than 50% of the inter-model dispersion in key variables for the surface climate such as the evapotranspiration. We therefore developed statistical tools to reconstruct the impacts of LUC on the surface albedo and the evapotranspiration using present-day observations and the land-cover maps prescribed in the LSMs here assessed. The analyses carried out here show that current uncertainties in the climate impacts of LUC are in major part the result of the land-surface parameterizations used in climate models and, hence, could be reduced with a more thoroughly evaluation of LSMs
Boisier, Juan Pablo. "Évaluer les impacts robustes du changement d'usage des sols sur le climat des 150 dernières années et sur le climat projeté pour le siècle prochain." Phd thesis, Ecole Polytechnique X, 2012. http://pastel.archives-ouvertes.fr/pastel-00787972.
Kiss, Laurence. "Impact des incendies sur les communautés de gastéropodes terrestres en basse Provence calcaire." Aix-Marseille 3, 2002. http://www.theses.fr/2002AIX30084.
Fire is a major disturbance within Mediterranean ecosystems, but its consequences on land snail communities and their subsequent recolonisation patterns are little studied. The aims of the present study are: (1) to define the short-; middle- and long-term impact of fire on land snail communities, (2) to analyse the consequences of successive fires during a short period of time on malacofaunas, and (3) to reveal the patterns of post-fire recolonisation within these communities. Land snail communities are highly resilient. Although fire induces a drastic reduction of their abundance, species richness is little affected and all the ecological groups are represented within the first post-fire year. Malacofaunas do not show patterns of post-fire succession. In fact, recolonisation patterns are complex and depend on diffuse refuges, located within burned areas and which are due to varying fire severity, but also on the biogeography and history of the sampling sites
Bossay, Sébastien. "Impact de la variabilité solaire sur l’ozone de la moyenne atmosphère." Electronic Thesis or Diss., Versailles-St Quentin en Yvelines, 2015. http://www.theses.fr/2015VERS002V.
A large part of the natural variability of the atmosphere and climate is related to solar variability. One of the forcing mechanisms of solar variability is based on perturbations of the middle atmosphere (stratosphere, mesosphere), particularly through ozone variations (photochemical processes), that then propagate through the troposphere to the surface. The thesis focuses on the first stage of this forcing mechanism, i.e. perturbations of ozone associated with solar variability and more specifically at the 27-day solar rotational time scales. The relationship between ozone and solar variability is studied not only using several time series of satellite data (MLS and GOMOS) but also results of a chemistry-climate model (LMDz-Reprobus) over analysis windows varying from 1 to 15 years. The mean ozone sensitivity to the 27-day solar cycle (% of ozone variation for 1% change in solar forcing) is characterized by positive values from 10 to 1 hPa with a maximum of 0.4 at 3 hPa. This sensitivity varies strongly depending on the size of the analysis window indicating that the solar signal can be masked by the dynamical variability, even during periods of strong solar activity. The dispersion of the results is found to be anti-correlated with the amplitude of the solar rotational fluctuations that are related to the phase of the 11-year solar cycle. In the mesosphere, ozone is found to be anti-correlated with solar variability with a maximum around 80 km. This corresponds exactly to the altitude of the maximum in the solar-induced enhancement of OH, the dominant radical in the destruction of mesospheric ozone
Ramel, Romain. "Impacts des processus de surface sur le climat en Afrique de l'Ouest." Phd thesis, Université Joseph Fourier (Grenoble), 2005. http://tel.archives-ouvertes.fr/tel-00009125.
Péden, Romain. "Impact du changement climatique sur le métabolisme des protéines d’une espèce clé des communautés intertidales, Mytilus edulis (L.)." Thesis, Le Havre, 2016. http://www.theses.fr/2016LEHA0015/document.
Intertidal organisms live in a fluctuating environment. The blue mussel Mytilus edulis is a key species of those ecosystems and are largely use as sentinel species. Global warming associated with anthropization will expose mussels to contaminations together with increased temperatures. In addition, more frequent heatwaves are expected. In this work, mussels were collected at two sites depicting contrasted levels of contamination and thermal exposure in microcosm were conducted. Two acclimation scenarios were set up prior to exposure to an identical acute thermal stress. In order to decipher joint effects of acclimation and contamination on protein homeostasis, gill proteome comparisons were performed. High mortality was observed only for mussels collected at the contaminated site and acclimated to current temperatures. Concerning gill proteome analysis, organisms from the pristine site exhibit high abundance of thermal stress proteins. Proteoforms involved in anaerobic metabolism were also up-regulated. Interestingly, mussels acclimated to the higher temperatures show an enhanced response compare to the one acclimated to current temperatures. Concerning mussels from the contaminated site, the response appears more confusing, excepted for heat stress protein response. This may indicate deleterious effects of combined contamination and heat stress. Therefore, organisms acclimated to higher temperature display improved responses. In conclusion, mussels with a clean life history show better physiological abilities than individuals with contaminated life history. Moreover, organisms prepared to heat stress by higher acclimation temperatures also develop a more effective response
Fumière, Quentin. "Impact du changement climatique sur les précipitations extrêmes dans le sud-est de la France : apport des modèles résolvant la convection profonde." Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30239.
The Mediterranean region and more particularly the South-East of France are affected by intense rainfall episodes during the autumn. Determining the future evolution of these events is a major scientific and societal challenge. The objective of this PhD thesis is to study at very high resolution and at climate scales the past representation and future evolution of these intense rainfall events. The approach here is based on the analysis of simulations of a family of explicit deep convection regional climate models (cprcms, 2-3 km) and on the exploitation of a new database of kilometric and hourly precipitation observations : comephore. The evaluation of the cprcms revealed a high added-value of explicit convection models compared with parameterized convection models (12.5 km) for the representation of daily and especially sub-daily extreme precipitation. The robustness of this added value has been showed to changes in cnrm-arome configurations (version, domain and model driving).The added value was also verified in 4 other rcm/cprcm pairs from the cordex fps-convection program. The study of precipitation changes based on 10-year simulations of the four cprcms did not provide a significant response of change in extreme precipitation. It is very natural climate variability is likely to dominate the future response of extreme precipitation over periods of 10 years, which implies that even at the end of the 21st century and in a scenario with high green house-gases emissions, it is likely that some decades will be wetter and others less so than decades of the current climate. It is therefore necessary to extend the simulations to increase the robustness of multi-model results. In addition, the 10-year change results with cnrm-arome are not representative of the changes over 30 years. The 30-year scenario simulation with cnrm-arome according to the rcp8.5 projection for the end of the century suggests an increase in extreme daily and especially hourly precipitation in the Cévennes and more particularly in Roussillon (+15% per degree of warming). In scenario mode, it was possible to show that cprcms can significantly change the rain response to climate change simulated by standard resolution rcms. This work is the first intensive scientific exploitation of the arome model in climate mode. The results obtained open up many possibilities for its future use to study climate at very high resolution and in particular extreme events
Dubois, Louise. "Impact des interventions du Fonds de solidarité des travailleurs du Québec (FTQ) sur le climat des relations de travail." Mémoire, Université de Sherbrooke, 1994. http://hdl.handle.net/11143/8603.
Bigot, Sylvain. "Les précipitations et la convection profonde en Afrique centrale : cycle saisonnier, variabilité interannuelle et impact sur la végétation." Dijon, 1997. http://www.theses.fr/1997DIJO1023.
This study establishes the coherent signals of the climatic variability and its connections in central Africa from a rainfall data base (1951-90), as well as satellite data and a reanalysis of the data from gcm. The water vapour advections over central Africa originate in the southern Atlantic Ocean with greater intraseasonal changes than those observed at the interannual scale. The heart of the Congo basin is also a regional source of divergence which is present for most of the year, and which redistributes water towards the Sahel or south-eastern Zaire. The surface conditions, for example topography and forestry, are important. In addition, the monthly olr reflects the rainfall of central Africa associated with deep convection and tropical circulation on global scale, but is not a good indicator of rainfall for all regions and all periods of the year. Central Africa is not a uniform rainfall area which varies homogeneously at interannual scale. Nevertheless, many analogies can be mad with other African areas. The enso signal is particularly visible in the deep convection of central Africa. Each enso occurrence corresponds with a modulation of the amplitude of the semi-annual rain cycle in the Congo-Gabon area, proving the predictive power of the sst. The rainfall modulation of the Atlantic, pacific and Indian sst's in central Africa is linked to a change in the east-west circulation due to the modification of the instable areas. The thermal variations in the southern Atlantic also impose a change in latitude of the itcz and the advections. The phenological mapping of rainforests using ndvi identifies different forestry behaviours and indicates certain spatio-temporal differences. A time lag is often observed between the rainfall and the forestry productivity. It is difficult to extract a bioclimatic signal due to the instrumental bias, but the interannual variations of the ndvi of the rca and northern Zaire are explained by the rainfall
Crombet, Yann. "Impact du réchauffement climatique et de l'acidification des océans sur les diatomées." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM4030.
Specifically orientated on the diatoms' phytoplanktonic group, this work tryed to understand the impact of warming and ocean acidification on diatoms and aimed at understand the taxon's response to the ongoing climate change. Amospheric pCO2 increase since the first industrial revolution lead to the augmentation of dissoveld inorganic carbon (DIC) concentration in the surface ocean, and thus to the ocean acidification, accompanied by an ocean surface warming leading finally to the extension of oligotrophic areas well stratified and nutrient depleted. Different in situ and lab techniques were used in order to better understand the diatom role in oligotrophic system and their response to warming and acidification in an oligotrophic chemostat, limited by phosphate
Routhier, Guillaume. "Les impacts perçus d'une formation à la créativité sur le potentiel créateur des participants, la créativité au travail, et le climat d'équipe." Thèse, Université de Sherbrooke, 2013. http://hdl.handle.net/11143/6477.
Orgeval, Tristan d'. "Impact du changement climatique sur le cycle de l'eau en Afrique de l'Ouest : modélisation et incertitudes." Paris 6, 2006. http://www.theses.fr/2006PA066624.
Kaimuddin, Awaluddin Halirin. "Impact du changement climatique sur la distribution des populations de poissons. Approche par SIG, modèles et scénarios d'évolution du climat." Thesis, Brest, 2016. http://www.theses.fr/2016BRES0039/document.
Understanding connectivities among species distributions, biodiversity, marine habitats and climate change is necessary for the design of an effective conservation management, such as in the implementation of marine protected area (MPA). In this study, we observed the richness of 89 "rare" or "exotic" fish species (observed outside their known distribution range) related to climate change. We modeled and predicted their seasonal distributions according to the species ecological niches (determined in this study) using the GIS model. Superposing the models of all species using GIS, we determined the preferential zones or zones of high biodiversity (hotspots) over time. The GIS approach offers an alternative to measure seasonal species richness in poor-data areas. This approach allowed also species track movement over time. This information could be then used to measure the effectiveness of MPA positioning related to the hotspot areas. Our study area covers a wide latitudinal range of the Eastern Atlantic waters, from the warm tropical/subtropical waters to the temperate waters. This area is located in three large marine ecosystems: the Canary current, the South European Atlantic Shelf and the Celtic Seas. The transitional zone in the central region has well known for its sensitivity to the detection of climate change. From 1982 to 2012, the SST in all of studied ecosystems has increased consistently over time, with magnitude and trend varied among ecosystems. The change of number of species in each decadal period differed among ecosystems. Increasing number of species in an ecosystem was generally followed by decreasing trend in adjacent ecosystems. Species ecological niches were obtained by extracting the environmental values in the location of species occurrence at the time of observation. The environmental data and the occurrence records used were at global scale, and the methods yields coherent results with the results obtained from observational studies. The flexibility of GIS Model used in this study allowed us to follow the evolution of species seasonal distribution over time. Generally, most of the studied species showed a northbound trend in their distribution. These northbound tendencies were more evident in the middle region, confirming the effect of global warming in shifting marine species distribution. This approach provides an alternative of measuring seasonal richness of poor-known species and/or modeling in poor-data areas. The results present a complete picture of predictive number of species in an area over time. MPAs superficial analysis by country (countries lying in the study area) showed that UK has the highest number of MPA and the largest protected areas, following by France and Mauritania. Frequencies of the MPAs touched by the hotspot were strongly influenced by seasonal variations. Thus, considering seasonal variations in a conservation effort could preserve species adaptive variation under environmental changes. Overall, our works provide several alternative methods for species distribution studies and for studies poor-known species in data-poor area. The results provide evidences of ocean warming effect in shifting marine fish distribution
Mami, Amina. "Impact des changements climatiques sur la disponibilité et la gestion des ressources en eau : cas du bassin versant de la Tafna." Thesis, Toulouse, INPT, 2020. http://www.theses.fr/2020INPT0110.
North West Algeria is one of the areas most sensitive to climate variability and change, where the decrease in rainfall has been marked along the North of Africa. The SWAT semi-distributed conceptual model is implemented with calibration and validation over a considerable period of time at the level of the Tafna watershed. The use and performance evaluation of the bias correction methods of the regional climate models of Cordex-Africa project, and their impact on hydrology during the reference period has been the subject of a whole chapter in order to study climate changes and their impacts on the hydrological cycle during the future period 2020-2099 at the scale of the studied region. The most significant trends were marked for decreases in precipitation throughout the 21st century. These decreases affected all components of the hydrological cycle from the river discharge to evapotranspiration. The SWAT model allowed us to represent on a temporal as well as spatial scale the distribution of the various hydrological components, river discharge, surface runoff at any point of the sub-watersheds, precipitation, lateral flow, soil water content, and evapotranspiration during the reference period and trends changes during future periods studied in this work. These results allowed us to define the impact of rainfall reduction on these hydrological components during the two months covered in this study, January and July, as well as to see the distribution, trends and interactions of all the months of the year. The hydrological components (runoff, evapotranspiration, etc.) are impacted by the decrease in rainfall during the future period of around -35%, this impact is visible, during the wet months with a decline in the river discharge and the soil water content varying towards -40%, and the lateral flow as well as the evapotranspiration of around -30%. However, the overestimation of RCMs during the summer period reversed the trend towards increased rainfall as well as hydrological components. In order to have a general view of the trend results obtained in this study, we evaluated the degree of drought using standardized drought indices, using certain components such as precipitation, evapotranspiration and runoff. These indices used allowed us to assign an estimation of drought comprise between moderate and severe on the Tafna basin
Martinez-Rey, Jorge. "Impact du changement climatique et l’acidification des océans sur le cycle océanique de l’azote." Electronic Thesis or Diss., Versailles-St Quentin en Yvelines, 2015. http://www.theses.fr/2015VERS009V.
The marine nitrogen cycle is responsible for two climate feedbacks in the Earth System. Firstly, it modulates thefixed nitrogen pool available for phytoplankton growth and hence it modulates in part the strength of thebiological pump, one of the mechanisms contributing to the oceanic uptake of anthropogenic CO2. Secondly, thenitrogen cycle produces a powerful greenhouse gas and ozone (O3) depletion agent called nitrous oxide (N2O).Future changes of the nitrogen cycle in response to global warming, ocean deoxygenation and oceanacidification are largely unknown. Processes such as N2-fixation, nitrification, denitrification and N2Oproduction will experience changes under the simultaneous effect of these three stressors. Global oceanbiogeochemical models allow us to study such interactions. Using NEMO-PISCES and the CMIP5 modelensemble we project changes in year 2100 under the business-as-usual high CO2 emissions scenario in globalscale N2-fixation rates, nitrification rates, N2O production and N2O sea-to-air fluxes adding CO2 sensitivefunctions into the model parameterizations. Second order effects due to the combination of global warming intandem with ocean acidification on the fixed nitrogen pool, primary productivity and N2O radiative forcingfeedbacks are also evaluated in this thesis
Lopez, Paulina. "Impact de la variabilité climatique sur la cryosphère du Campo de Hielo Norte : apport de la télédétection." Montpellier 2, 2007. http://www.theses.fr/2007MON20195.
Cuccia, Cédric. "Impacts du changement climatique sur la phénologie du Pinot noir en Bourgogne." Thesis, Dijon, 2013. http://www.theses.fr/2013DIJOS094/document.
The viticulture is an important economic and cultural sector in Burgundy. The current climate change raises a number of issues including its impact on crops. In this thesis, the idea is to develop a methodology to address the problem: what are the potential impacts of changes in temperature on the phenology of Pinot noir in Burgundy for years 2031-2048?The evolution of temperatures in Burgundy since 1961 is characterized by a positive temperature shift at the end of the 1980s followed by a period where the temperature increases of about 1.5 ° C.One of the interests of this thesis is to develop, following a strategy developed during the thesis, a spatial database conducted over the period 1989-2009 to estimate the ability of the WRF model to reproduce the climate Burgundy by disaggregating large scale data. The model reproduces satisfactorily the seasonal and spatial variability in global climate despite bias (cold on the Tx and hot on the Tn).To regionalize the climate change, WRF was used to disaggregate data from the scenario SRES/A2 on the periods 1970-1987 and 2031-2048. After being evaluated and inter-compared three phenological models, using average temperatures data to simulate the dates of occurrence of phenological stages of Pinot Noir, have been applied to these decompositions.The impact of warming temperatures on the horizon 2031-2048 (SRES/A2), estimated at 1.35 ° C on average, is characterized by an earlier flowering and veraison of about 7 and 15 days respectively. The interstadial duration is also reduced of about 5 days
Torres, Olivier. "Représentation des flux turbulents à l’interface air-mer et impact sur les transports de chaleur et d’eau dans un modèle de climat." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLV002/document.
The turbulent fluxes at the air-sea interface represent the link between the ocean and the atmosphere and therefore play a major role in the climate system. In climate models, turbulent processes are subgrid scale processes, not explicitly resolved, and must therefore be parameterized. They are estimated from atmospheric and oceanic state variables using mathematical models called “bulk parameterizations”. This thesis aims to characterize and understand the links between the representation of turbulent fluxes at the air-sea interface and the behavior of a climate model at different time scales in tropical regions. To study these links, I developed a modeling strategy using an atmospheric 1D model (SCM), an oceanic (OGCM) or atmospheric (AGCM) general circulation model and a coupled model (GCM). The analysis of SCM simulations allows us to study the direct response of a model to modifications of the turbulent fluxes parameterization. It is shown that it regulates the amount of water, energy and momentum available to the system and therefore its behavior. It can thus represent more than 60% of simulated latent heat flux differences between two climate models in convective periods. The spatial impact of the parameterization of turbulent fluxes is studied through AGCM simulations. They highlight the link between parameterization, its effect on large-scale moisture and temperature gradients, and thus its influence on atmospheric circulation. The study of OGCM simulations underlines the main role of the wind for the behavior of the tropical oceans. If the wind drives changes in SST due to its impact on ocean dynamics and mainly on the equatorial undercurrent, humidity, temperature and radiative flux only influence the ocean surface and are therefore of lesser importance. Finally, the analysis of GCM simulations highlights the feedbacks and the adjustment generated by the modification of turbulent fluxes. When coupling the two components, the ocean acts as a buffer and absorbs the modification of the turbulent fluxes, which leads to a modification of the SST. The adjustment that occurs causes a modification of the atmospheric variables which leads to a new state of equilibrium of the system. The parameterization of surface turbulent fluxes acts at first order on the energy equilibrium of a coupled model and can therefore lead to different simulated climate state. Since this study is focused on the tropics, an interesting perspective would be to extend the study of the turbulent fluxes representation to other spatio-temporal scales (i.e. extra-tropical areas / daily frequency). This would make it possible to validate the systematic behavior of the parameterizations defined in this thesis on a global scale
Torres, Olivier. "Représentation des flux turbulents à l’interface air-mer et impact sur les transports de chaleur et d’eau dans un modèle de climat." Electronic Thesis or Diss., Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLV002.
The turbulent fluxes at the air-sea interface represent the link between the ocean and the atmosphere and therefore play a major role in the climate system. In climate models, turbulent processes are subgrid scale processes, not explicitly resolved, and must therefore be parameterized. They are estimated from atmospheric and oceanic state variables using mathematical models called “bulk parameterizations”. This thesis aims to characterize and understand the links between the representation of turbulent fluxes at the air-sea interface and the behavior of a climate model at different time scales in tropical regions. To study these links, I developed a modeling strategy using an atmospheric 1D model (SCM), an oceanic (OGCM) or atmospheric (AGCM) general circulation model and a coupled model (GCM). The analysis of SCM simulations allows us to study the direct response of a model to modifications of the turbulent fluxes parameterization. It is shown that it regulates the amount of water, energy and momentum available to the system and therefore its behavior. It can thus represent more than 60% of simulated latent heat flux differences between two climate models in convective periods. The spatial impact of the parameterization of turbulent fluxes is studied through AGCM simulations. They highlight the link between parameterization, its effect on large-scale moisture and temperature gradients, and thus its influence on atmospheric circulation. The study of OGCM simulations underlines the main role of the wind for the behavior of the tropical oceans. If the wind drives changes in SST due to its impact on ocean dynamics and mainly on the equatorial undercurrent, humidity, temperature and radiative flux only influence the ocean surface and are therefore of lesser importance. Finally, the analysis of GCM simulations highlights the feedbacks and the adjustment generated by the modification of turbulent fluxes. When coupling the two components, the ocean acts as a buffer and absorbs the modification of the turbulent fluxes, which leads to a modification of the SST. The adjustment that occurs causes a modification of the atmospheric variables which leads to a new state of equilibrium of the system. The parameterization of surface turbulent fluxes acts at first order on the energy equilibrium of a coupled model and can therefore lead to different simulated climate state. Since this study is focused on the tropics, an interesting perspective would be to extend the study of the turbulent fluxes representation to other spatio-temporal scales (i.e. extra-tropical areas / daily frequency). This would make it possible to validate the systematic behavior of the parameterizations defined in this thesis on a global scale
Tchoupé, Makougoum Christelle Flore. "Changement climatique au Mali : impact de la secheresse sur l'agriculture et stratégies d'adaptation." Thesis, Université Clermont Auvergne (2017-2020), 2018. http://www.theses.fr/2018CLFAD011.
Mali is a West African country where agriculture is mainly rain-fed, therefore essentially dependent on climatic conditions. This strong dependence between agriculture and climate makes it an interesting field of investigation, and especially with agriculture being the mainstay of Mali’s economy. Relying on theoretical and empirical methods, this thesis aims to contribute to a better understanding of the impact of climate change on agricultural production and to a better understanding of farmers’ practices that make it possible to adapt to climate change. The first chapter of this thesis focused on the manifestations of climate change and their impacts on cereals production. Analysis of correlations between series of climate and agricultural data indicates that, overall, climate change has a damaging effect on cereals yields. After this analysis at the production level, we turned to the analysis of producer’s behavior. Hence, the second chapter focuses on the managerial performance of farmers. Using a stochastic frontier analysis, we found that a part of the farmers’ inefficiency is due to climate change. The results also revealed that even though there is inefficiency due to climate, it is low compared to technical inefficiency of the farmer. Subsequently, we concentrated on how to maintain or increase agricultural production in a context of climate change. For this purpose, the third chapter identifies the determinants of adaptation to climate change. We focused on agricultural adaptation practices that preserve the environment. We used a multinomial logit model. The analysis demonstrated that the socio-demographic characteristics of farm households, the biophysical characteristics of plots and the occurrence of a drought influence the adoption of adaptation strategies. Finally, the fourth chapter studies the determinants of farm mechanization using the Heckman selection model. The results suggest that drought reduces the odds of farm mechanization. We also found that the intensity of farm mechanization increases with increase of farm size and decreases with the increase of family workforce
Coronel, Benoît. "Impact des processus humides sur les dépressions des latitudes tempérées." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30340/document.
The objective of this thesis is to analyze the influence of moist processes on mid-latitude cyclones, and specifically the tracks of cyclones and the formation of strong winds near the surface. These researches have been made using idealized simulations of the mesoscale model Méso-NH. The first study focused on the effects of moist processes on the motion perpendicularly to the zonal jet axis, poleward. The main mechanism explaining this motion involves the nonlinear advection of the surface cyclone by the upper-level cyclonic and anticyclonic perturbations located on both sides of the surface cyclone. In the presence of humidity, the upper-level anticyclonic anomaly strengthens due to the latent heat release in the ascent zones, and the poleward motion is reinforced. The eastward motion of the cyclone is also reinforced with the inclusion of moist processes. The second study focuses on the formation of near-surface strong winds which are triggered by the so-called " sting-jets ". These jets correspond to descending air masses from the mid-troposphere near the cloud head down to the top of the boundary layer, and can trigger devastating surface winds. In the case where synoptic perturbations are initialized south of the baroclinic zonal jet, the bent-back warm front phase occurs, whereas when they are initialized on the zonal jet axis, the surface cyclone has a less active warm front. Thus, the formation of a sting-jet only occurs in the first case, and with a high vertical resolution. It is the geostrophic forcing in a globally neutral environment relative to conditional symmetric instability which facilitates the airstreams descent and the formation of the sting-jet
Ghirardi, Julie. "Impact de la tansition climatique Eocène - Oligocène sur les écosystèmes continentaux : Etude du bassin de Rennes." Thesis, Orléans, 2016. http://www.theses.fr/2016ORLE2093/document.
The study of past climate changes on the terrestrial realm provides clues to understand the mechanisms,chronology, and timing of ecosystems response to climate disturbances. The Eocene-Oligocene Transition(EOT) of the Eocene-Oligocene boundary (EOb) is well suited for this type of study because it records the last climatic transition between the greenhouse and icehouse modes via a misunderstood interval: thedoubthouse period. This climatic transition was studied through the analysis of organic-rich lacustrine sediments. After an astro-calibrated age model was set up, we reconstructed the evolution of vegetation by using molecular biomarkers specific of plant groups and of local climate (temperature and hydrological conditions) by using molecular and isotopic proxies. The climate record exhibits a marked cooling and drying at the EOT. The evolution of vegetation did not show any abrupt change but exhibited pronounced and rhythmic changes in phase with excentricity during an interval that started 1750 ka before the EOb and lasted until 300 ka after. This interval named Environmental Transition Interval (ETI) was warmer and wetter, and coincides with the doubthouse period. The start of the ETI is concomitant with changes in the recording of orbital parameters. The good expression of solar cycles in the sediments from that period attests to the setting or strengthening of ocean-atmosphere couplings linked to the establishment of the Antarctic icesheet. This work partly solves the uncertainties that prevailed on the doubthouse period
NETO, FERREIRA EDUARDO. "Une estimation de la variation de la constante solaire pendant le minimum de maunder et son impact sur le climat de la terre." Paris 7, 1993. http://www.theses.fr/1993PA077189.
Linden, Sandra van der. "Icy rivers heating up : modelling hydrological impacts of climate change in the (sub)arctic /." Amsterdam : Utrecht : Koninklijk Nederlands Aardrijkskundig Genootschap ; Faculteit Ruimtelijke Wetenschappen, Universiteit Utrecht, 2002. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=010495642&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
Chemison, Alizée. "Impacts d'une déstabilisation des calottes polaires sur le climat et les maladies vectorielles au XXIème siècle." Electronic Thesis or Diss., université Paris-Saclay, 2023. http://www.theses.fr/2023UPASJ007.
Mosquitoes, major vectors of diseases, are sensitive to rainfall which is necessary for their immature aquatic stages, and to temperature which affects their development and life cycle dynamics. Climate change can therefore impact the transmission of vector-borne diseases such as malaria, the world's major parasitic disease causing over 600,000 deaths per year, and Rift Valley Fever (RVF), a zoonotic disease decimating herds, causing health risks and catastrophic economic losses in Africa.The Intergovernmental Panel on Climate Change (IPCC) report provides climate scenarios for the 21st century with different standard greenhouse gas emission scenarios, named Representative Concentration Pathway (RCP). By 2080, the risk of malaria transmission is estimated to decrease in the Sahel region and to increase in the East African Plateau as a result of rising temperatures under the RCP8.5 scenario. Although paleoclimate studies show that melting ice sheet can induce abrupt climate change, state of the art IPCC future projections do not consider such a potential rapid destabilisation of polar ice sheets. However, the West Antarctic and Greenland ice sheet are vulnerable to climate change and even a partial melting would cause major climatic changes, even in tropical regions. No study has yet quantified the impact of an abrupt melting of the ice sheets on the distribution of malaria and RVF. This work is based on future climate numerical simulations using the coupled global climate model IPSL-CM5A-LR with RCP8.5 as radiative forcing. Simulations of freshwater release, corresponding to the accelerated and partial melting of the polar ice sheets, were carried out with different melting assumptions:- for Greenland, a freshwater flux equivalent to a global sea level rise of 0.5m, 1m, 1.5m and 3m is released into the North Atlantic;- for Antarctica, a quantity of freshwater equivalent to a global sea level rise of 3m is released off its western part.These continuous water inputs are prescribed from 2020 to 2070.This study showed that the oceanic and atmospheric impacts of a partial melting of Greenland are stronger on the global climate, and particularly on monsoons, than those associated with the melting of West Antarctica, probably due to the effect of the circumpolar current. Subsequently, only scenarios considering a partial melting of Greenland were used to study their impacts on malaria. Simulated and/or observed temperature and precipitation were used to drive mathematical models of malaria transmission risk. Five mathematical malaria models were used. An accelerated melting of Greenland leads to a southward shift of the American and African monsoons. Malaria risk increases in southern Africa, decreases in the Sahel and increases moderately on the East African Plateau.For the study of RVF, the Liverpool Rift Valley Fever (LVRF) model was validated at country scale by comparing simulations driven by observed daily temperatures and rainfall from climate reanalyses with different health data sets. Then, a potential correlation between simulated RVF transmission risk and the main regional climate variability modes (ENSO and DMI) is shown over the Rift African region. The model correctly reproduces RVF epidemics in Kenya, Somalia and Zambia, and to a lesser extent in Senegal and Mauritania. RVF risk increases over the epidemic areas in East Africa during the El Niño phenomenon
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
Velazquez, Garcia Alejandra. "Chemical and optical properties of particulate pollution in the Lille area, Northern France based on ATOLL observations." Electronic Thesis or Diss., Ecole nationale supérieure Mines-Télécom Lille Douai, 2023. http://www.theses.fr/2023MTLD0001.
The link between fine aerosol optical properties and their chemical composition is not yet well understood, and was investigated using long-term in situ observations performed at the “ATmospheric Observations in liLLe” platform from 2016 to 2020 using a combination of aerosol mass spectrometer, aethalometer, and nephelometer. Highly absorbing aerosols and a marked seasonality of the mass contribution of ammonium nitrate (AN) in spring were observed. We evidence that AN (35%) and carbonaceous aerosols (51%) are predominant regarding light extinction at 525 nm. Besides, a novel approach combining these in situ measurements to backtrajectories and emission inventories identifies a Brown Carbon (BrC) decrease within 24 hours after emission even during wintertime, pointing at a likely systematic underestimation of the contribution of residential heating (identified by the presence of BrC) to the aerosol absorption in the region
Bestion, Elvire. "Impact du changement climatique sur un vertébré ectotherme : de l'individu à la communauté." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30389.
Recent global change has dramatic impacts on biodiversity, through modifications in abiotic and biotic factors. Species vulnerability to changing climates depend for instance of its habitat, its position within the community and its thermal physiology. In this respect, ectotherm species are considered particularly vulnerable as their body temperature depend directly on their environment. We experimentally studied the impact of future climate change on an ectotherm vertebrate species, the common lizard (Zootoca vivipara). We used the Metatron, a system of semi-natural enclosures in which climatic conditions can be manipulated. We studied the impact of warmer climatic conditions (+2°C) on common lizard's population dynamics and extinction risk, and on population adaptation capacity through plasticity, selection and dispersal. We further investigated the impact of climate change at the community scale. We demonstrated that future climatic conditions pose a threat to common lizard. However, possibilities of adaptation exist through changes in phenology and physiology (preferred temperature and melanism). Finally, we show that changing climatic conditions have an impact on the entire communities, from plants and insects to microbial communities
Poisson, Blanche. "Impact du climat et de la tectonique sur l'évolution géomorphologique d'un piémont - Exemple du piémont Nord du Tian Shan depuis la fin du Pléistocène." Phd thesis, Université Paris Sud - Paris XI, 2002. http://tel.archives-ouvertes.fr/tel-00009710.
Lespinas, Franck. "Impacts du changement climatique sur l'hydrologie des fleuves côtiers en region Languedoc-Roussillon." Perpignan, 2008. http://www.theses.fr/2008PERP1261.
This thesis contributes to understanding the vulnerability of surface water resources of the region Languedoc-Roussillon address climate change. A detailed reconstruction hydroclimatic conditions was first performed over the period 1965-2004 considering the 6 mains rivers of the region. It has shown that the average annual temperature has risen approximately 1. 5°C, reflecting an increasing influence of systems of subtropical high pressure in the spring and summer. Precipitation did not reveal any significant trends, except for winter precipitation that decreased in the north-east of the study area. The average annual flows tended to decrease on all rivers in the region, but significantly only in the Pyrenean basins and downstream river Herault and Orb. The low flows have also become more severe for a large majority of hydrologic stations. The increase of evaporation seems to have played a major role in these evolutions. The simulations from climate models indicate that the temperature should continue to increase in the 21st century, especially in summer, while precipitations would likely decrease. The forcing of a hydrological model calibrated for each river from climate scenarios constructed by the end of the 21st century indicate a significant decline in flows during the period late spring - early autumn with a significant drying of the soil
Charrayre, François. "Modélisation de fermes de systèmes houlomoteurs : effets d’interactions entre systèmes à l’échelle de la ferme et impact sur le climat de vagues à l'échelle régionale." Thesis, Paris Est, 2015. http://www.theses.fr/2015PEST1097/document.
This thesis focuses on the development of a set of numerical tools to simulate different aspects of the wave-body interactions applied to the exploitation of wave energy converters (WEC). It was conducted under the ANR Monacorev project (project-ANR11 MONU-018-01, 2012-2015).The objective is to address the issue of the interactions at the scale of a farm of WECs (≈ 1 km), and to study the impact of one or more WEC farms at the regional scale (≈ 10km ) on the total wave field. Modeling and simulation methods adapted for each of these two scales are developed. Until now, the interactions between WECs was often studied by considering that the bottom was flat (the influence of a variable bathymetry on the wave field at the farm site being considered to be negligible), allowing to easily and quickly calculate the wave field and interactions through the use of linear potential theory. A practical application of this method is the yield estimation for a WEC farm and the optimization of the WEC position within a park. In the framework of the linear theory, this thesis proposes an original coupling methodology between a seakeeping (Aquaplus) and a wave propagation code in coastal areas (Artemis), which was developed and qualified. Simulations show that, for a given WEC farm configuration, effects of the bathymetry cannot systematically ignored. For example, the presence of a 10% slope close to a WEC farm can significantly modify the wave height, and thus affect the performance of the farm by several percent compared to the case with a uniformly flat bottom. At the regional coastal scale, it is also interesting to simulate and predict the impact of WEC farms on the wave field. At this scale, for efficiency reasons, a phase-averaged simulation of waves was preferred, based on the sea state spectral code TOMAWAC. The representation of the effects of a WEC through the use of a sink-term (concept for subtracting the energy equivalent to that absorbed by the WEC to the sea state energy spectrum), though incomplete due to the fact that the scattering effects are not taken into account, has been studied and tested. A new methodology taking into account these effects in a spectral code is presented here and tested with the aim to overcome these limitations. Discussions on the validity of these approaches allow us to propose possible future developments for the modeling of WEC farm at the regional scale
Hashoum, Hazem. "Impact du changement climatique sur les interactions biotiques en forêt méditerranéenne : approches chimique, écophysiologique et fonctionnelle." Thesis, Aix-Marseille, 2017. http://www.theses.fr/2017AIXM0480/document.
The aim of this thesis is to study allelopathic interactions in the downy oak forest in the mediterranean region and to consider how these interactions can be affected by climate change. We have shown that the dominant tree Q. pubescens and its companion species A. monspessulanum and C. coggygria have different allelopathic potentialities, evaluated in vitro on herbaceous target plants, depending on the phenological stage of the leaves, which could in natura affect the germination and growth of understory herbaceous plants. These differences in allelopathic effect may result not only from differences in the quantity of allelopathic compounds produced, but also from qualitative differences observed as a function of the phenological stage. This suggests that the allelopathic effect may vary over time to match the stage of development of the target herbaceous plants. On one of the target plants used in the bioassays, the allelopathic effects were further accentuated by changing the water and / or thermal conditions which suggests possible modifications of the allelopathic potential of the plants to be expected with climate change.Our results in the plant nursery showed the allelopathic potential of cotinus and pinus on the growth of oak seedlings, whatever the watering conditions (stressed or unstressed). By affecting in particular the biomass of the root system, the growth of which is a key element of the mediterranean species to resist the prolonged summer drought, these interactions could play an important role in the regeneration processes of downy oak