Intéractions aérosols-rayonnement-nuages et variabilité climatique en méditerranée - Approche par la modelisation régionale couplée

Le bassin méditerranéen est sujet à de nombreuses sources d'aérosols présentant une variabilité spatio-temporelle élevée. Ces aérosols interagissent de manière directe avec les rayonnements solaire et thermique, et de manière indirecte avec les nuages et la dynamique atmosphérique. Ils peuvent donc avoir un impact important sur le climat de cette région. Ce travail de thèse, à la frontière entre les projets HyMeX et ChArMEx, considère une approche par la modélisation régionale couplée pour répondre aux questions des interactions aérosols-rayonnement-nuages par rapport à la variabilité climatique de la région méditerranéenne. Afin de mieux caractériser les aérosols méditerranéens, une nouvelle climatologie mensuelle et interannuelle d'épaisseur optique a été développée à partir d'une combinaison de produits satellites et de modèles. Ce jeu de données, disponible pour tous les modèles régionaux de climat en Méditerranée sur la période 1979-2012, a été mis au point dans le but d'obtenir la meilleure estimation possible du contenu atmosphérique en aérosols pour les cinq types considérés (sulfates, carbone suie et organique, poussières désertiques et sels marins). Des ensembles de simulations réalisées sur la période 2003-2009 avec et sans aérosols montrent un impact majeur sur le climat régional. Cet impact se caractérise par un forçage radiatif négatif en surface (dû à la diffusion et l'absorption du rayonnement solaire incident) de -15 W.m−2 en moyenne annuelle sur la mer Méditerranée, par un refroidissement induit en surface à la fois sur mer et sur terre de l'ordre de 0.5◦C en moyenne annuelle, par une diminution moyenne des précipitations ainsi que par des changements de nébulosité. Le cycle saisonnier et les structures spatiales du climat méditerranéen sont ainsi significativement modifiés, ainsi que certaines situations spécifiques comme la canicule de juillet 2006 qui a été renforcée par la présence d'aérosols désertiques. Le rôle essentiel de la température de surface de la mer Méditerranée dans la réponse du climat aux aérosols est mis en évidence, et permet de comprendre les modifications induites des flux air-mer (notamment la diminution de la perte en chaleur latente) et ses conséquences sur le climat régional. La convection océanique en mer Méditerranée est également renforcée par la présence d'aérosols. En outre, on démontre que la diminution des aérosols anthropiques observée depuis plus de trente ans a contribué significativement aux tendances climatiques de rayonnement (représentant 81 ± 15 % de l'éclaircissement) et de température (représentant 23 ± 5 % du réchauffement) observées en Europe et en Méditerranée. D'autre part, un schéma interactif d'aérosols a été mis en place dans le modèle atmosphérique ALADIN-Climat afin de pouvoir comprendre les processus liés aux aérosols à l'échelle quotidienne. On montre ici la capacité de ce schéma de simuler de manière réaliste les aérosols présents en Méditerranée, notamment dans le cas des intrusions de poussières désertiques observées pendant la campagne de mesures ChArMEx/TRAQA. Un exercice d'intercomparaison avec d'autres modèles intégrant les aérosols désertiques confirme la performance du nouveau schéma. De plus, utiliser un schéma prognostique d'aérosols au lieu d'une climatologie mensuelle permet de mieux reproduire les variations quotidiennes et en particulier les extrêmes de rayonnement et de température en surface. Cela induit aussi une modification du climat moyen, dans la mesure où les variations des aérosols et de leurs effets dépendent des régimes de temps et de la nébulosité. Cette thèse conclut ainsi à la nécessité pour les systèmes climatiques de modélisation régionale en Méditerranée de bien prendre en compte les effets radiatifs des aérosols et leur variabilité spatiotemporelle, y compris à haute fréquence. Les impacts de ces effets radiatifs sur de nombreux paramètres (rayonnement, température, humidité, flux air-mer, circulation océanique, etc.) sont en effet démontrés à différentes échelles d'espace et de temps (variabilité quotidienne, cycle saisonnier, tendances climatiques, extrêmes, structures spatiales). Ce travail a aussi montré que le couplage entre l'atmosphère et la mer Méditerranée est indispensable pour des études aérosols-climat dans cette région. ABSTRACT : The Mediterranean basin is affected by numerous and various aerosols which have a high spatiotemporal variability. These aerosols directly interact with solar and thermal radiation, and indirectly with clouds and atmospheric dynamics. Therefore they can have an important impact on the regional climate. This work, located at the boundary between the ChArMEx and HyMeX programs, considers a coupled regional modeling approach in order to address the questions of the aerosol-radiation-cloud interactions with regards to the climate variability over the Mediterranean. In order to improve the characterization of Mediterranean aerosols, a new interannual monthly climatology of aerosol optical depth has been developed from a blended product based on both satellitederived and model-simulated datasets. This dataset, available for every regional climate model over the Mediterranean for the 1979-2012 period, has been built to obtain the best possible estimate of the atmospheric aerosol content for the five species at stake (sulfate, black carbon, organic matter, desert dust and sea salt particles). Simulation ensembles, which have been carried out over the 2003-2009 period with and without aerosols, show a major impact on the regional climate. This impact is characterized by a negative surface radiative forcing (due to the absorption and the scattering of the solar incident radiation) of -15 W.m−2 on annual average over the Mediterranean Sea, an induced surface cooling both over land and sea of about -0.5◦C on annual average, a decrease in precipitation as well as cloud cover changes. The seasonal cycle and the spatial patterns of the Mediterranean climate are significantly modified, as well as some specific situations such as the heat wave in July 2006 strengthened by the presence of desert dust particles. The essential role of the Mediterranean sea surface temperature is highlighted, and enables to understand the induced changes on air-sea fluxes (notably the decrease in the latent heat loss) and the consequences on regional climate. Oceanic convection is also strengthened by aerosols. In addition, the decrease in anthropogenic aerosols observed for more than thirty years is shown to significantly contribute to the observed Euro-Mediterranean climatic trends in terms of surface radiation (representing 81 ± 15 % of the brightening) and temperature (representing 23 ± 5 % of the warming). Besides, an interactive aerosol scheme has been developed in the atmospheric model ALADINClimate in order to better understand aerosol processes at the daily scale. This scheme shows its ability to represent correctly the aerosol patterns over the Mediterranean, especially with regards to dust outbreaks that were measured during the ChArMEx/TRAQA field campaign. An intercomparison exercise with several dust models confirms the performance of the new scheme. Moreover, the use of a prognostic aerosol scheme instead of a monthly climatology enables to better reproduce the daily variations of surface radiation and temperature and related extremes. This also leads to changes in the mean climate, insofar as aerosol variations and their effects depend on weather regimes and cloud cover. Finally this study concludes with the need for regional climate system models over the Mediterranean to take into account the radiative aerosol effects and their spatio-temporal variability, including at high frequency. The impacts of these radiative effects on numerous parameters (radiation, temperature, humidity, ocean-atmosphere fluxes, oceanic circulation, etc.) are indeed shown and understood at different space and time scales (daily variability, seasonal cycle, climate trends, spatial structures). This work has also shown the importance of the coupling between the atmosphere and the Mediterranean Sea for aerosol-climate studies in this region

Assessing English Language Learners: Bridges to Educational Equity: Connecting Academic Language Proficiency to Student Achievement

Assessing English Language Learners: Bridges to Educational Equity: Connecting Academic Language Proficiency to Student Achievement is a comprehensive resource that intends to build bridges that promote educational equity, particularly in the areas of instruction and assessment. The book consists of two parts each of which includes four chapters. Part I, entitled “Assessment as a Context for Teaching and Learning: Bridges to Equity,” focuses on the issues of equity concerning the assessment of language learners, more specifically, English Language Learners (ELLs). In the introduction to Part I, Gottlieb provides her rationale for focusing on assessment equity for ELLs, where she mentions the increasing numbers of linguistically and culturally diverse students in U.S. schools, the different life and educational experiences of ELLs, some of whom are refugees and immigrants, the importance of promoting equal educational opportunities for all students as well as these groups of students, and so on. Gottlieb provides some facts showing the changing demographics in U.S. public schools. According to Gottlieb, while language learners is an umbrella term descriptive of all students in pre-kindergarten through twelfth grade, there are also many other terms that can be associated with this population of learners, such as linguistically and culturally diverse students, heritage language learners, English language learners, dual language learners, emergent bilinguals, long-term English language learners, etc. The author lists educators and their primary instructional and assessment responsibilities for the education of language learners, which can serve as a useful guide in determining the varied expectations from different educators in regard to their contribution to comprehensive services for ELLs. Gottlieb describes linguistically and culturally responsive classrooms and schools, and asserts that establishing a responsive learning environment is the only way to optimize learning opportunities and to effectively and equally serve the increasingly heterogeneous U.S. public school student population

Données personnelles : Comment nous avons peu à peu accepté d’en perdre le contrôle

Article paru dans The Conversation considéré comme un médi

Assessing English Language Learners: Bridges to Educational Equity: Connecting Academic Language Proficiency to Student Achievement

Assessing English Language Learners: Bridges to Educational Equity: Connecting Academic Language Proficiency to Student Achievement is a comprehensive resource that intends to build bridges that promote educational equity, particularly in the areas of instruction and assessment. The book consists of two parts each of which includes four chapters. Part I, entitled “Assessment as a Context for Teaching and Learning: Bridges to Equity,” focuses on the issues of equity concerning the assessment of language learners, more specifically, English Language Learners (ELLs). The author lists educators and their primary instructional and assessment responsibilities for the education of language learners, which can serve as a useful guide in determining the varied expectations from different educators in regard to their contribution to comprehensive services for ELLs. Gottlieb describes linguistically and culturally responsive classrooms and schools, and asserts that establishing a responsive learning environment is the only way to optimize learning opportunities and to effectively and equally serve the increasingly heterogeneous U.S. public school student population

Le spectre d’un fichage biométrique des manifestants

Peut-on refuser que ses empreintes digitales et génétiques soient prélevées en garde à vue ? Que deviennent les données ainsi collectées

Segmenting video frame images using genetic algorithms

Image segmentation plays an important role in computer vision. It is a process that partitions a digital image into several meaningful regions ,by identifying regions of an image that have common properties while separating regions that are dissimilar. The image segmentation problem is posed as an optimization procedure. In this thesis, an optimization approach based on genetic algorithm is introduced for finding optimal image segmentation. The design and implementation of genetic algorithm image segment or (GSAI) system are described. GSAI system employs finds optimal value using genetic operators "crossover operator and mutation operator". The different proposed / implementation segmentation methods of the GSAI system were tested using Gray image are taken from one films and with size 352x240 pixels for video frames images of In this is work focused on genetic algorithm coefficients which affect in direct and active way in the work of GA to study and analysis dependable video images which are taken from video clips after partitioning to multiple frames

Partially Purification M Protein from Streptococcus Pyogens and Molecular Study of Some Virulence Factors

The current study was conducted to isolation one type of surface protein of Streptococcus pyogens this protein separated using partially purification method. Purifiction  process include precipitation of crude  M protein  one peak of this protein was appeared, the best precipitate rate was 30% . PCR assay were performed to identify the presence of some genes related to pathogenicity in bacteria responsible from Tonsillitis .Streptococcus pyogens represented the largest causative agent of inflammation of the tonsil so the study revealed the presence of certain gene in some isolate of bacteria, including the gene SpeB that gave large proportions in the study isolates 12 out of 37 at a rate of (32.4%). Keywords : S.pyogens , Tonsillitis , M protein ,PCR ,Spe

Improved technique for hiding data in a colored and a monochrome image

Find a new way to hide the different types of confidential and important text files inside the images without noticing any change or distortion of the information in the images after the process of concealment or attempt to be detected by hackers. And then extract these texts and retrieved on demand without loss or loss or distortion of any of its content. The algorithm was used to hide the different text in different image formats using (256) elements, monochrome and color where about 4500 characters were hidden in a monochrome image and about 900 characters in a color image and with a hiding distance (S) where N = 3, key = 3. The overall error rate is low (0.05-0.17) and no distortions were observed on the resulting imag