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Etude du couplage fort par spectroscopie optique dans des microcavités GaN élaborées sur silicium

Abstract : As an essential part of the atmosphere, aerosol particles play an important role both on the air quality than on the earth radiative budget. This work is a contribution to a better understanding of the formation mechanisms of new particles by nucleation in the natural atmosphere. Our approach is orientated to the observation of the first steps of the particles formation, associated to a study of the environmental conditions which favoured or limited its development. This experimental study is based on a long data set at two high elevation sampling sites: the puy de Dôme (1465 m a.s.l., France) and the ABC-Pyr observatory, located at the Everest foot (5079 m a.s.l.). First, we characterize the puy de Dôme aerosol physical properties, and observe that the concentrations show a high seasonal variability, with a maximum in summer. We propose representative size distribution for different air mass types (marine, continental, regional) under background conditions. The atmospheric composition variability on the ABC-Pyr site also brings new information about the troposphere background and the local/regional and long distance transport influence. At the two sites, a high nucleation event frequency is observed for the first time at high altitudes. A statistical study shows that photochemistry has an important impact on nucleation and growth and that cloud also have a significant effect which is more complex. The altitude seems to be, in our studies, a location which favours nucleation events. We note that this phenomenon has a high spatial extension and its influence on the radiative balance and climate cannot be anodyne.
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Hervé Venzac. Etude du couplage fort par spectroscopie optique dans des microcavités GaN élaborées sur silicium. Physique Atmosphérique et Océanique [physics.ao-ph]. Université Blaise Pascal - Clermont-Ferrand II, 2008. Français. ⟨NNT : 2008CLF21856⟩. ⟨tel-00730608⟩

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