Cette thèse s’intéresse aux ondes de gravité et à la turbulence dans la région de la tropopause tropicale (TTL pour tropical tropopause layer, entre 14 et 18 km d’altitude), et à leurs impacts sur les cirrus.Dans un premier temps, les fluctuations de température et de vent vertical induites dans la TTL par les ondes de gravité sont quantifiées et caractérisées à partir de mesures provenant de vols de ballons stratosphériques longue durée. Les perturbations observées sont comparées aux champs de fluctuations résolues par différents modèles atmosphériques globaux. À la lumière des observations, différentes méthodes de paramétrisation des fluctuations de température sont discutées.Dans un second temps, l’influence des ondes équatoriales et de gravité sur la microphysique des cirrus est étudiée. On considère d’abord l’impact des ondes de gravité de haute fréquence sur la nucléation des cristaux de glace. La question du rôle des anomalies de vent vertical induites par les ondes de basse fréquence sur le transport de la glace est ensuite abordée et son impact quantifié à l’aide d’observations in situ. Enfin, on étudie la formation et l’évolution d’un cirrus de grande échelle à l’aide de simulations numériques. Parmi les différents processus en jeu (radiatifs,...), on montre l’importance d’une onde équatoriale de grande échelle dans la structuration et l’évolution du champ nuageux.Dans une dernière partie, les fluctuations de vents de petite échelle dans la TTL, interprétées comme de la turbulence, sont étudiées à partirdes observations avion de la campagne ATTREX au-dessus de l’océan Pacifique. Leur impact sur le transport vertical de différents traceurs est quantifié. Il est inférieur à l’impact de l’upwelling équatorial de grande échelle mais néanmoins significatif. / Atmospheric waves and turbulence and their impacts on cirrus clouds in the Tropical Tropopause Layer (TTL, 14-18 km altitude) are studied using in situ observations, numerical simulations and theoretical approaches.First, long-duration stratospheric balloon measurements are used to analyze Lagrangian temperature and vertical wind fluctuations induced by gravity waves at the tropical tropopause. The amplitude and intermittency of wave fluctuations are assessed, and the observations are compared with resolved wave fluctuations in atmospheric models. Methods to parameterize Lagrangian temperature fluctuations are then discussed.Then, some impacts of waves on cirrus clouds microphysics are examined. We first consider the influence of high frequency gravity waves on the ice nucleation process. Next, we explore the interplay between ice crystal sedimentation and advection by the wind perturbations induced by low frequency waves. At last, we use numerical simulations to investigate the formation of a large-scale cirrus in the TTL. We demonstrate the role of large-scale equatorial waves and quantify the relevance of different processes (dynamics, radiative heating,...) in the cloud evolution.Finally, small-scale wind fluctuations, interpreted as turbulent bursts, are characterized using aircraft measurements from the ATTREX campaign in the tropical Pacific. The impact of the fluctuations on vertical mixing and on the TTL tracer budget is quantified. The vertical transport induced by turbulent mixing is found to be smaller than that induced by mean tropical upwelling, but nonetheless significant.

Made available in DSpace on 2016-04-28T14:16:34Z (GMT). No. of bitstreams: 1 Erivelton Alves Bizerra.pdf: 8926443 bytes, checksum: 178bf86156f6b57ad9075f66503b1aac (MD5) Previous issue date: 2008-10-07 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Alberto Santos Dumont (1873-1932) is well known in Brazil and France for his pioneer contributions to the development of the airplane. However, before that, he also helped to develop the technique of balloon flight, obtaining important results of directed flight using motorized airships. This works analyses his contribution to this field. This dissertation presents, first, an historical account of the invention of balloons, from the early Chinese flying lights to the introduction of hot-air and hydrogen balloons in Europe, in the 18th century. Next, this work analyses the issue of balloon flight control. After the first manned flights, in 1783, there was a strong interest for this invention and there were several proposals of controlling its flight. The first attempts of flying motorised balloons, which attained a moderate success, were made in 1852, using a heavy steam machine. Other attempts were made afterwards, using several kinds of motors (including electrical ones), but they did not attain practical results. In the late 19th century, Santos Dumont began to develop airships driven by internal combustion engines (such as those used by automobiles) and obtained good results. In 1901 he was awarded the Deutsch de la Meurthe Prize, when he demonstrated the control of a motorised balloon that was able to make a flight round the Eiffel Tower. Finally, this dissertation analyses Santos Dumont s scientific and technical knowledge, as well the technical difficulties involved in the control of airships, at that time / Alberto Santos Dumont (1873-1932) é muito conhecido, no Brasil e na França, por seus trabalhos pioneiros sobre aviação, mas também desenvolveu, antes disso, a técnica de vôo em balões, obtendo importantes resultados na dirigibilidade com aparelhos dotados de motor. Este trabalho analisa sua contribuição neste campo. Esta dissertação apresenta primeiramente um histórico da invenção dos balões, desde as luzes voadoras chinesas até a introdução de balões de ar quente e de hidrogênio na Europa, no século XVIII. Em seguida, a dissertação analisa a história da dirigibilidade dos balões. Logo após os primeiros vôos tripulados, em 1783, surgiu um enorme interesse pelo invento e foram propostas formas de proporcionar-lhe dirigibilidade. As primeiras tentativas, com algum grau de sucesso, de balões dotados de motores ocorreram em 1852, utilizando uma máquina a vapor. Houve depois algumas poucas tentativas, utilizando motores de vários tipos (inclusive elétricos), mas não foram obtidos bons resultados. Nos últimos anos do século XIX, Santos Dumont iniciou o desenvolvimento de balões movidos por motores de combustão interna (como os de automóveis) e conseguiu bons resultados. Em 1901, obteve o Prêmio Deutsch de la Meurthe, demonstrando o controle de um balão motorizado que contornou a Torre Eiffel. Por fim, a dissertação analisa os conhecimentos científicos e técnicos de Santos Dumont, bem como as dificuldades técnicas que era necessário superar para conseguir controlar o vôo dos balões, na época