The Experts below are selected from a list of 3249 Experts worldwide ranked by ideXlab platform
Joao Paulo Araujo Fernandes De Queiroz - One of the best experts on this subject based on the ideXlab platform.
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Latent Heat Loss and sweat gland histology of male goats in an equatorial semi arid environment
International Journal of Biometeorology, 2014Co-Authors: Cintia Carol De Melo Costa, Steffan Edward Octávio Oliveira, Alex Sandro Campos Maia, Jose Domingues Fontenele Neto, Joao Paulo Araujo Fernandes De QueirozAbstract:The objective of this work was to quantify the Heat Loss by cutaneous evaporation of goats in an equatorial semi-arid environment. The Latent Heat Loss from the body surfaces of these ten undefined breed goats was measured using a ventilated capsule in sun and shade and in the three body regions (neck, flank and hindquarters). Skin samples from these three regions were histologically analyzed to relate the quantity of sweat glands, the area of sweat glands and the epithelium thickness of each of these regions to the Heat Loss by cutaneous evaporation of the examined goats. The epithelium thickness that was measured varied significantly for body regions with different quantities and areas of sweat glands (P < 0.01). Among the body regions that were examined, the samples from the neck demonstrated the highest epithelium thickness (16.23 ± 0.13 μm). However, the samples of sweat glands from the flank had the biggest area (43330.51 ± 778.71 μm2) and quantity per square centimeter (390 ± 9 cm−2). After the animals were exposed to sun, the flanks lost the greatest amount of Heat by cutaneous evaporation (73.03 ± 1.75 W m−2) and possessed the highest surface temperatures (39.47 ± 0.18 °C). The histological characteristics may have influenced the Heat Loss by cutaneous evaporation that was observed in the flank region after the animals were exposed to sun.
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Latent Heat Loss of dairy cows in an equatorial semi arid environment
International Journal of Biometeorology, 2012Co-Authors: Roberto Gomes Da Silva, Leonardo Lelis De Macedo Costa, Alex Sandro Campos Maia, Joao Paulo Araujo Fernandes De QueirozAbstract:The present study aimed to evaluate evaporative Heat transfer of dairy cows bred in a hot semi-arid environment. Cutaneous (E S) and respiratory (E R) evaporation were measured (810 observations) in 177 purebred and crossbred Holstein cows from five herds located in the equatorial semi-arid region, and one herd in the subtropical region of Brazil. Rectal temperature (T R), hair coat surface temperature (T S) and respiratory rate (F R) were also measured. Observations were made in the subtropical region from August to December, and in the semi-arid region from April to July. Measurements were done from 1100 to 1600 hours, after cows remained in a pen exposed to the sun. Environmental variables measured in the same locations as the animals were black globe temperature (T G), air temperature (T A), wind speed (U), and partial air vapour pressure (P V). Data were analysed by mixed models, using the least squares method. Results showed that average E S and E R were higher in the semi-arid region (117.2 W m−2 and 44.0 W m−2, respectively) than in the subtropical region (85.2 W m−2 and 30.2 W m−2, respectively). Herds and individual cows were significant effects (P < 0.01) for all traits in the semi-arid region. Body parts did not affect T S and E S in the subtropical region, but was a significant effect (P < 0.01) in the semi-arid region. The average flank T S (42.8°C) was higher than that of the neck and hindquarters (39.8°C and 41.6°C, respectively). Average E S was higher in the neck (133.3 W m−2) than in the flank (116.2 W m−2) and hindquarters (98.6 W m−2). Coat colour affected significantly both T S and E S (P < 0.01). Black coats had higher T S and E S in the semi-arid region (41.7°C and 117.2 W m−2, respectively) than white coats (37.2°C and 106.7 W m−2, respectively). Rectal temperatures were almost the same in both subtropical and semi-arid regions. The results highlight the need for improved management methods specific for semi-arid regions.
P N Vinayachandran - One of the best experts on this subject based on the ideXlab platform.
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mechanisms of formation of the arabian sea mini warm pool in a high resolution ocean general circulation model
Journal of Geophysical Research, 2007Co-Authors: Jaison Kurian, P N VinayachandranAbstract:An Ocean General Circulation Model of the Indian Ocean with high horizontal (0.25 degrees x 0.25 degrees) and vertical (40 levels) resolutions is used to study the dynamics and thermodynamics of the Arabian Sea mini warm pool (ASMWP), the warmest region in the northern Indian Ocean during January-April. The model simulates the seasonal cycle of temperature, salinity and currents as well as the winter time temperature inversions in the southeastern Arabian Sea (SEAS) quite realistically with climatological forcing. An experiment which maintained uniform salinity of 35 psu over the entire model domain reproduces the ASMWP similar to the control run with realistic salinity and this is contrary to the existing theories that stratification caused by the intrusion of low-salinity water from the Bay of Bengal into the SEAS is crucial for the formation of ASMWP. The contribution from temperature inversions to the warming of the SEAS is found to be negligible. Experiments with modified atmospheric forcing over the SEAS show that the low Latent Heat Loss over the SEAS compared to the surroundings, resulting from the low winds due to the orographic effect of Western Ghats, plays an important role in setting up the sea surface temperature (SST) distribution over the SEAS during November March. During March-May, the SEAS responds quickly to the air-sea fluxes and the peak SST during April-May is independent of the SST evolution during previous months. The SEAS behaves as a low wind, Heat-dominated regime during November-May and, therefore, the formation and maintenance of the ASMWP is not dependent on the near surface stratification.
Alex Sandro Campos Maia - One of the best experts on this subject based on the ideXlab platform.
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Latent Heat Loss and sweat gland histology of male goats in an equatorial semi arid environment
International Journal of Biometeorology, 2014Co-Authors: Cintia Carol De Melo Costa, Steffan Edward Octávio Oliveira, Alex Sandro Campos Maia, Jose Domingues Fontenele Neto, Joao Paulo Araujo Fernandes De QueirozAbstract:The objective of this work was to quantify the Heat Loss by cutaneous evaporation of goats in an equatorial semi-arid environment. The Latent Heat Loss from the body surfaces of these ten undefined breed goats was measured using a ventilated capsule in sun and shade and in the three body regions (neck, flank and hindquarters). Skin samples from these three regions were histologically analyzed to relate the quantity of sweat glands, the area of sweat glands and the epithelium thickness of each of these regions to the Heat Loss by cutaneous evaporation of the examined goats. The epithelium thickness that was measured varied significantly for body regions with different quantities and areas of sweat glands (P < 0.01). Among the body regions that were examined, the samples from the neck demonstrated the highest epithelium thickness (16.23 ± 0.13 μm). However, the samples of sweat glands from the flank had the biggest area (43330.51 ± 778.71 μm2) and quantity per square centimeter (390 ± 9 cm−2). After the animals were exposed to sun, the flanks lost the greatest amount of Heat by cutaneous evaporation (73.03 ± 1.75 W m−2) and possessed the highest surface temperatures (39.47 ± 0.18 °C). The histological characteristics may have influenced the Heat Loss by cutaneous evaporation that was observed in the flank region after the animals were exposed to sun.
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Latent Heat Loss of dairy cows in an equatorial semi arid environment
International Journal of Biometeorology, 2012Co-Authors: Roberto Gomes Da Silva, Leonardo Lelis De Macedo Costa, Alex Sandro Campos Maia, Joao Paulo Araujo Fernandes De QueirozAbstract:The present study aimed to evaluate evaporative Heat transfer of dairy cows bred in a hot semi-arid environment. Cutaneous (E S) and respiratory (E R) evaporation were measured (810 observations) in 177 purebred and crossbred Holstein cows from five herds located in the equatorial semi-arid region, and one herd in the subtropical region of Brazil. Rectal temperature (T R), hair coat surface temperature (T S) and respiratory rate (F R) were also measured. Observations were made in the subtropical region from August to December, and in the semi-arid region from April to July. Measurements were done from 1100 to 1600 hours, after cows remained in a pen exposed to the sun. Environmental variables measured in the same locations as the animals were black globe temperature (T G), air temperature (T A), wind speed (U), and partial air vapour pressure (P V). Data were analysed by mixed models, using the least squares method. Results showed that average E S and E R were higher in the semi-arid region (117.2 W m−2 and 44.0 W m−2, respectively) than in the subtropical region (85.2 W m−2 and 30.2 W m−2, respectively). Herds and individual cows were significant effects (P < 0.01) for all traits in the semi-arid region. Body parts did not affect T S and E S in the subtropical region, but was a significant effect (P < 0.01) in the semi-arid region. The average flank T S (42.8°C) was higher than that of the neck and hindquarters (39.8°C and 41.6°C, respectively). Average E S was higher in the neck (133.3 W m−2) than in the flank (116.2 W m−2) and hindquarters (98.6 W m−2). Coat colour affected significantly both T S and E S (P < 0.01). Black coats had higher T S and E S in the semi-arid region (41.7°C and 117.2 W m−2, respectively) than white coats (37.2°C and 106.7 W m−2, respectively). Rectal temperatures were almost the same in both subtropical and semi-arid regions. The results highlight the need for improved management methods specific for semi-arid regions.
Jaison Kurian - One of the best experts on this subject based on the ideXlab platform.
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mechanisms of formation of the arabian sea mini warm pool in a high resolution ocean general circulation model
Journal of Geophysical Research, 2007Co-Authors: Jaison Kurian, P N VinayachandranAbstract:An Ocean General Circulation Model of the Indian Ocean with high horizontal (0.25 degrees x 0.25 degrees) and vertical (40 levels) resolutions is used to study the dynamics and thermodynamics of the Arabian Sea mini warm pool (ASMWP), the warmest region in the northern Indian Ocean during January-April. The model simulates the seasonal cycle of temperature, salinity and currents as well as the winter time temperature inversions in the southeastern Arabian Sea (SEAS) quite realistically with climatological forcing. An experiment which maintained uniform salinity of 35 psu over the entire model domain reproduces the ASMWP similar to the control run with realistic salinity and this is contrary to the existing theories that stratification caused by the intrusion of low-salinity water from the Bay of Bengal into the SEAS is crucial for the formation of ASMWP. The contribution from temperature inversions to the warming of the SEAS is found to be negligible. Experiments with modified atmospheric forcing over the SEAS show that the low Latent Heat Loss over the SEAS compared to the surroundings, resulting from the low winds due to the orographic effect of Western Ghats, plays an important role in setting up the sea surface temperature (SST) distribution over the SEAS during November March. During March-May, the SEAS responds quickly to the air-sea fluxes and the peak SST during April-May is independent of the SST evolution during previous months. The SEAS behaves as a low wind, Heat-dominated regime during November-May and, therefore, the formation and maintenance of the ASMWP is not dependent on the near surface stratification.
Darmaraki Sofia - One of the best experts on this subject based on the ideXlab platform.
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Canicules océaniques en Méditerranée : détection, variabilité passée et évolution future
HAL CCSD, 2019Co-Authors: Darmaraki SofiaAbstract:The Mediterranean Sea is considered a "Hot Spot" region for future climate change and depending on the greenhouse emission scenario, the annual mean basin sea surface temperature (SST) is expected to increase from +1.5 °°C to +3 °°C at the end of the 21st century relative to present-day. This significant SST rise is likely to intensify episodes of extreme warm ocean temperatures in the basin, named as Marine Heatwaves (MHWs), that are known to exert substantial pressure on marine ecosystems and related fisheries around the world. In this context, the main aim of this PhD work is to study the past variability and future evolution of MHWs in the Mediterranean Sea. We propose a detection method for long lasting and large-scale summer MHWs, using a local, climatological 99th percentile threshold, based on present-climate daily SST. MHW probability of occurrence and characteristics in terms of spatial variability and temporal evolution are then investigated, using additional integrated indicators (e.g. duration, intensity, spatial extension, severity) to describe past and future events. Within the PhD and depending on the applications, the detection method is applied to various datasets : In-situ observation at buoys, high-resolution satellite product, various high- resolution and fully-coupled Regional Climate System Models including the recently developed CNRM-RCSM6 and the multi-model (5), multi-scenario (3) Med-CORDEX ensemble. The detection method is first tested on the 2003 MHW in order to assess its sensitivity to various tuning parameters. We conclude that its characterization is partly sensitive to the algorithm setting. Hindcast and historical mode simulations show that models are able to capture well observed MHW characteristics. We then assess past surface MHW variability (1982-2017) and their underlying driving mechanisms using the CNRM-RCSM6 model. We examine their characteristics from surface to 55m depth, where most thermal stress-related mass mortalities of Mediterranean ecosystems have been observed in the past. The analysis indicates an increase in duration and intensity of surface events with time, while MHWs of 2003, 2012 and 2015 are identified as the most severe events of the period. In particular, an anomalous increase in shortwave radiation and a lower-than-normal vertical diffusion and Latent Heat Loss appeared to be responsible for the development of the MHW 2003, with wind playing a key role in the intensity of temperature anomalies at the sea surface. Differences on the dominant forcing, however, are sometimes evident in the different subbasin.We finally use the Med-CORDEX RCSM ensemble to assess the future MHW evolution in the basin over 1976-2100. Our results suggest longer and more severe events with higher global-warming rates. By 2100 and under RCP8.5, simulations project at least one long- lasting MHW every year, up to 3 months longer, about 4 times more intense and 42 times more severe than present-day events. Their occurrence is expected between June-October affecting at peak the entire basin. Their evolution is found to mainly occur due to an increase in the mean SST but an increase in daily SST variability plays also a noticeable role. Up to mid-21st century MHW characteristics rise independently of the choice of the emission scenario, whose influence becomes more evident by the end of the period.L'objectif principal de ce travail de thèse est d'étudier la variabilité passée et l'évolution future des épisodes de températures océaniques anormalement chaudes en Méditerranée. Ces évènements, appelés canicules océaniques ou Marine Heatwaves en anglais (MHW), sont connues pour exercer une pression considérable sur les écosystèmes marins et les pêcheries associées un peu partout dans le monde. Nous proposons une nouvelle méthode de détection automatique des MHWs d'été basée sur le 99ème centile de la température quotidienne de la surface de la mer (TSM) en climat présent et tenant compte de la diversité géographique de la zone. La probabilité d'occurrence des MHWs et leurs caractéristiques spatio-temporelles sont ensuite étudiées. D'autres indicateurs intégrés tels que la durée, l'intensité, l'extension spatiale maximale ou la sévérité permettent de compléter la description des MHWs. Au cours de cette thèse et en fonction des applications, la méthode de détection est appliquée à différents types de données : observations in-situ aux bouées, produit satellitaire et différents modèles haute résolution et couplés haute fréquence du système climatique régional (RCSMs pour Regional Climate System Model en anglais) y compris le nouveau modèle CNRM-RCSM6 et l'ensemble Med-CORDEX multi-modèle (5) et multi-scénarios (3). L'algorithme de détection est d'abord testé sur la MHW de 2003 afin de montrer qu'il est peu sensible aux différents paramètres de réglage. L'évaluation des simulations rétrospectives et historiques montrent que les RCSMs sont capables dans l'ensemble de bien reproduire l'occurrence et les caractéristiques des MHWs observées par satellite. Nous étudions ensuite la variabilité passée des MHWs de surface (1982-2017) ainsi que leurs facteurs explicatifs en utilisant le modèle CNRM-RCSM6. Nous examinons, leurs caractéristiques entre 20-55 m de profondeur, là où la plupart des mortalités de masse liées au stress thermique des écosystèmes méditerranéens ont été observées dans le passé. L'analyse indique une augmentation de la durée et de l'intensité des évènements de surface au fil du temps, tandis que les MHWs de 2003, 2012 et 2015 sont détectées comme les évènements les plus sévères de la période. Par ailleurs, pour la canicule 2003 des différences importantes dans la contribution des échanges air-mer et de la diffusion vertical de chaleur sont mis en évidence pour les différents sous-bassins méditerranéens. Nous montrons également que la tension de vent joue un rôle clé sur l'intensité des anomalies de température en surface ainsi que leur propagation verticale. Enfin, nous utilisons l'ensemble Med-CORDEX de RCSMs pour évaluer l'évolution future des MHWs dans la région sur la période 1976-2100. Nos résultats suggèrent des évènements plus longs et plus sévères au fur et à mesure que le réchauffement climatique s'intensifie. D'ici à 2100 et dans le cadre du scénario le plus pessimiste (RCP8.5), les simulations projettent au moins une MHW de longue durée chaque année, jusqu'à 3 mois plus longue, environ 4 fois plus intense et 40 fois plus sévère que les évènements actuels. On s'attend à ce qu'elles se produisent entre juin et octobre, affectant au plus fort de leur extension l'ensemble du bassin. Cette évolution s'explique principalement par une augmentation de la TSM moyenne, mais l'augmentation de la variabilité quotidienne de la TSM joue également un rôle notable. Jusqu'au milieu du 21ème siècle, les caractéristiques des MHWs augmentent indépendamment du choix du scénario d'émission, dont l'influence devient plus évidente à la fin de la période. Enfin, l'analyse individuelle des modèles révèle différentes familles de réponses au changement climatique. Ces différences s'expliquent plus probablement par le choix du modèle global forçant, plutôt que par les biais individuels des modèles régionaux
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Mediterranean marine Heatwaves : detection, past variability and future evolution
2019Co-Authors: Darmaraki SofiaAbstract:L'objectif principal de ce travail de thèse est d'étudier la variabilité passée et l'évolution future des épisodes de températures océaniques anormalement chaudes en Méditerranée. Ces évènements, appelés canicules océaniques ou Marine Heatwaves en anglais (MHW), sont connues pour exercer une pression considérable sur les écosystèmes marins et les pêcheries associées un peu partout dans le monde. Nous proposons une nouvelle méthode de détection automatique des MHWs d'été basée sur le 99ème centile de la température quotidienne de la surface de la mer (TSM) en climat présent et tenant compte de la diversité géographique de la zone. La probabilité d'occurrence des MHWs et leurs caractéristiques spatio-temporelles sont ensuite étudiées. D'autres indicateurs intégrés tels que la durée, l'intensité, l'extension spatiale maximale ou la sévérité permettent de compléter la description des MHWs. Au cours de cette thèse et en fonction des applications, la méthode de détection est appliquée à différents types de données : observations in-situ aux bouées, produit satellitaire et différents modèles haute résolution et couplés haute fréquence du système climatique régional (RCSMs pour Regional Climate System Model en anglais) y compris le nouveau modèle CNRM-RCSM6 et l'ensemble Med-CORDEX multi-modèle (5) et multi-scénarios (3). L'algorithme de détection est d'abord testé sur la MHW de 2003 afin de montrer qu'il est peu sensible aux différents paramètres de réglage. L'évaluation des simulations rétrospectives et historiques montrent que les RCSMs sont capables dans l'ensemble de bien reproduire l'occurrence et les caractéristiques des MHWs observées par satellite. Nous étudions ensuite la variabilité passée des MHWs de surface (1982-2017) ainsi que leurs facteurs explicatifs en utilisant le modèle CNRM-RCSM6. Nous examinons, leurs caractéristiques entre 20-55 m de profondeur, là où la plupart des mortalités de masse liées au stress thermique des écosystèmes méditerranéens ont été observées dans le passé. L'analyse indique une augmentation de la durée et de l'intensité des évènements de surface au fil du temps, tandis que les MHWs de 2003, 2012 et 2015 sont détectées comme les évènements les plus sévères de la période. Par ailleurs, pour la canicule 2003 des différences importantes dans la contribution des échanges air-mer et de la diffusion vertical de chaleur sont mis en évidence pour les différents sous-bassins méditerranéens. Nous montrons également que la tension de vent joue un rôle clé sur l'intensité des anomalies de température en surface ainsi que leur propagation verticale. Enfin, nous utilisons l'ensemble Med-CORDEX de RCSMs pour évaluer l'évolution future des MHWs dans la région sur la période 1976-2100. Nos résultats suggèrent des évènements plus longs et plus sévères au fur et à mesure que le réchauffement climatique s'intensifie. D'ici à 2100 et dans le cadre du scénario le plus pessimiste (RCP8.5), les simulations projettent au moins une MHW de longue durée chaque année, jusqu'à 3 mois plus longue, environ 4 fois plus intense et 40 fois plus sévère que les évènements actuels. On s'attend à ce qu'elles se produisent entre juin et octobre, affectant au plus fort de leur extension l'ensemble du bassin. Cette évolution s'explique principalement par une augmentation de la TSM moyenne, mais l'augmentation de la variabilité quotidienne de la TSM joue également un rôle notable. Jusqu'au milieu du 21ème siècle, les caractéristiques des MHWs augmentent indépendamment du choix du scénario d'émission, dont l'influence devient plus évidente à la fin de la période. Enfin, l'analyse individuelle des modèles révèle différentes familles de réponses au changement climatique. Ces différences s'expliquent plus probablement par le choix du modèle global forçant, plutôt que par les biais individuels des modèles régionaux.The Mediterranean Sea is considered a "Hot Spot" region for future climate change and depending on the greenhouse emission scenario, the annual mean basin sea surface temperature (SST) is expected to increase from +1.5 °°C to +3 °°C at the end of the 21st century relative to present-day. This significant SST rise is likely to intensify episodes of extreme warm ocean temperatures in the basin, named as Marine Heatwaves (MHWs), that are known to exert substantial pressure on marine ecosystems and related fisheries around the world. In this context, the main aim of this PhD work is to study the past variability and future evolution of MHWs in the Mediterranean Sea. We propose a detection method for long lasting and large-scale summer MHWs, using a local, climatological 99th percentile threshold, based on present-climate daily SST. MHW probability of occurrence and characteristics in terms of spatial variability and temporal evolution are then investigated, using additional integrated indicators (e.g. duration, intensity, spatial extension, severity) to describe past and future events. Within the PhD and depending on the applications, the detection method is applied to various datasets : In-situ observation at buoys, high-resolution satellite product, various high- resolution and fully-coupled Regional Climate System Models including the recently developed CNRM-RCSM6 and the multi-model (5), multi-scenario (3) Med-CORDEX ensemble. The detection method is first tested on the 2003 MHW in order to assess its sensitivity to various tuning parameters. We conclude that its characterization is partly sensitive to the algorithm setting. Hindcast and historical mode simulations show that models are able to capture well observed MHW characteristics. We then assess past surface MHW variability (1982-2017) and their underlying driving mechanisms using the CNRM-RCSM6 model. We examine their characteristics from surface to 55m depth, where most thermal stress-related mass mortalities of Mediterranean ecosystems have been observed in the past. The analysis indicates an increase in duration and intensity of surface events with time, while MHWs of 2003, 2012 and 2015 are identified as the most severe events of the period. In particular, an anomalous increase in shortwave radiation and a lower-than-normal vertical diffusion and Latent Heat Loss appeared to be responsible for the development of the MHW 2003, with wind playing a key role in the intensity of temperature anomalies at the sea surface. Differences on the dominant forcing, however, are sometimes evident in the different subbasin.We finally use the Med-CORDEX RCSM ensemble to assess the future MHW evolution in the basin over 1976-2100. Our results suggest longer and more severe events with higher global-warming rates. By 2100 and under RCP8.5, simulations project at least one long- lasting MHW every year, up to 3 months longer, about 4 times more intense and 42 times more severe than present-day events. Their occurrence is expected between June-October affecting at peak the entire basin. Their evolution is found to mainly occur due to an increase in the mean SST but an increase in daily SST variability plays also a noticeable role. Up to mid-21st century MHW characteristics rise independently of the choice of the emission scenario, whose influence becomes more evident by the end of the period
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Canicules océaniques en Méditerranée : détection, variabilité passée et évolution future
2019Co-Authors: Darmaraki SofiaAbstract:L'objectif principal de ce travail de thèse est d'étudier la variabilité passée et l'évolution future des épisodes de températures océaniques anormalement chaudes en Méditerranée. Ces évènements, appelés canicules océaniques ou Marine Heatwaves en anglais (MHW), sont connues pour exercer une pression considérable sur les écosystèmes marins et les pêcheries associées un peu partout dans le monde. Nous proposons une nouvelle méthode de détection automatique des MHWs d'été basée sur le 99ème centile de la température quotidienne de la surface de la mer (TSM) en climat présent et tenant compte de la diversité géographique de la zone. La probabilité d'occurrence des MHWs et leurs caractéristiques spatio-temporelles sont ensuite étudiées. D'autres indicateurs intégrés tels que la durée, l'intensité, l'extension spatiale maximale ou la sévérité permettent de compléter la description des MHWs. Au cours de cette thèse et en fonction des applications, la méthode de détection est appliquée à différents types de données : observations in-situ aux bouées, produit satellitaire et différents modèles haute résolution et couplés haute fréquence du système climatique régional (RCSMs pour Regional Climate System Model en anglais) y compris le nouveau modèle CNRM-RCSM6 et l'ensemble Med-CORDEX multi-modèle (5) et multi-scénarios (3). L'algorithme de détection est d'abord testé sur la MHW de 2003 afin de montrer qu'il est peu sensible aux différents paramètres de réglage. L'évaluation des simulations rétrospectives et historiques montrent que les RCSMs sont capables dans l'ensemble de bien reproduire l'occurrence et les caractéristiques des MHWs observées par satellite. Nous étudions ensuite la variabilité passée des MHWs de surface (1982-2017) ainsi que leurs facteurs explicatifs en utilisant le modèle CNRM-RCSM6. Nous examinons, leurs caractéristiques entre 20-55 m de profondeur, là où la plupart des mortalités de masse liées au stress thermique des écosystèmes méditerranéens ont été observées dans le passé. L'analyse indique une augmentation de la durée et de l'intensité des évènements de surface au fil du temps, tandis que les MHWs de 2003, 2012 et 2015 sont détectées comme les évènements les plus sévères de la période. Par ailleurs, pour la canicule 2003 des différences importantes dans la contribution des échanges air-mer et de la diffusion vertical de chaleur sont mis en évidence pour les différents sous-bassins méditerranéens. Nous montrons également que la tension de vent joue un rôle clé sur l'intensité des anomalies de température en surface ainsi que leur propagation verticale. Enfin, nous utilisons l'ensemble Med-CORDEX de RCSMs pour évaluer l'évolution future des MHWs dans la région sur la période 1976-2100. Nos résultats suggèrent des évènements plus longs et plus sévères au fur et à mesure que le réchauffement climatique s'intensifie. D'ici à 2100 et dans le cadre du scénario le plus pessimiste (RCP8.5), les simulations projettent au moins une MHW de longue durée chaque année, jusqu'à 3 mois plus longue, environ 4 fois plus intense et 40 fois plus sévère que les évènements actuels. On s'attend à ce qu'elles se produisent entre juin et octobre, affectant au plus fort de leur extension l'ensemble du bassin. Cette évolution s'explique principalement par une augmentation de la TSM moyenne, mais l'augmentation de la variabilité quotidienne de la TSM joue également un rôle notable. Jusqu'au milieu du 21ème siècle, les caractéristiques des MHWs augmentent indépendamment du choix du scénario d'émission, dont l'influence devient plus évidente à la fin de la période. Enfin, l'analyse individuelle des modèles révèle différentes familles de réponses au changement climatique. Ces différences s'expliquent plus probablement par le choix du modèle global forçant, plutôt que par les biais individuels des modèles régionaux.The Mediterranean Sea is considered a "Hot Spot" region for future climate change and depending on the greenhouse emission scenario, the annual mean basin sea surface temperature (SST) is expected to increase from +1.5 °°C to +3 °°C at the end of the 21st century relative to present-day. This significant SST rise is likely to intensify episodes of extreme warm ocean temperatures in the basin, named as Marine Heatwaves (MHWs), that are known to exert substantial pressure on marine ecosystems and related fisheries around the world. In this context, the main aim of this PhD work is to study the past variability and future evolution of MHWs in the Mediterranean Sea. We propose a detection method for long lasting and large-scale summer MHWs, using a local, climatological 99th percentile threshold, based on present-climate daily SST. MHW probability of occurrence and characteristics in terms of spatial variability and temporal evolution are then investigated, using additional integrated indicators (e.g. duration, intensity, spatial extension, severity) to describe past and future events. Within the PhD and depending on the applications, the detection method is applied to various datasets : In-situ observation at buoys, high-resolution satellite product, various high- resolution and fully-coupled Regional Climate System Models including the recently developed CNRM-RCSM6 and the multi-model (5), multi-scenario (3) Med-CORDEX ensemble. The detection method is first tested on the 2003 MHW in order to assess its sensitivity to various tuning parameters. We conclude that its characterization is partly sensitive to the algorithm setting. Hindcast and historical mode simulations show that models are able to capture well observed MHW characteristics. We then assess past surface MHW variability (1982-2017) and their underlying driving mechanisms using the CNRM-RCSM6 model. We examine their characteristics from surface to 55m depth, where most thermal stress-related mass mortalities of Mediterranean ecosystems have been observed in the past. The analysis indicates an increase in duration and intensity of surface events with time, while MHWs of 2003, 2012 and 2015 are identified as the most severe events of the period. In particular, an anomalous increase in shortwave radiation and a lower-than-normal vertical diffusion and Latent Heat Loss appeared to be responsible for the development of the MHW 2003, with wind playing a key role in the intensity of temperature anomalies at the sea surface. Differences on the dominant forcing, however, are sometimes evident in the different subbasin.We finally use the Med-CORDEX RCSM ensemble to assess the future MHW evolution in the basin over 1976-2100. Our results suggest longer and more severe events with higher global-warming rates. By 2100 and under RCP8.5, simulations project at least one long- lasting MHW every year, up to 3 months longer, about 4 times more intense and 42 times more severe than present-day events. Their occurrence is expected between June-October affecting at peak the entire basin. Their evolution is found to mainly occur due to an increase in the mean SST but an increase in daily SST variability plays also a noticeable role. Up to mid-21st century MHW characteristics rise independently of the choice of the emission scenario, whose influence becomes more evident by the end of the period. Further analysis finally reveals different climate change responses in certain configurations, more likely linked to their driving global climate model rather than to the individual regional model biases. This study provides a better understanding of Mediterranean Sea sensitivity to climate change considering for the first time the uncertainties related to global and regional climate models. We believe that this constitutes key information for the marine ecosystems and marine-related activities and societies in the basin that are under considerable risks due to the devastating effects of these events
