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Télédétection Multi-satellite des Propriétés des Systèmes Convectifs de l'Océan Indien ; Observation pendant la Mousson d'Hiver.

Abstract : This study is based on the INDOEX (Indian Ocean Experience) measurements in 1999 winter period. The goal of this work is firstly to examine the properties of mesoscale convective systems (MCSs) using METEOSAT-5 infrared images and secondly to investigate the precipitations by using DMSP SSM/I and TRMM TMI microwaves data. Thirdly, present a comparison of the orbit data sampling between different satellites and introduce the advantage of a new satellite Megha-Tropiques. In the first part, the METEOSAT-5 infrared consecutive images have been used to study the MCSs over Indian Ocean. A cloud tracking algorithm was applied to compute the radiative and morphological parameters of each MCS. Then the trajectory during the entire life cycle of MCS was reconstructed and their possible situations have been identified such as dissipation, split and mergence. The map of occurrence frequency shows that most of the systems occur in the Inter-tropical Convergence Zone (ITCZ) spreading from Indonesia to North of Madagascar, the other two distinct areas are the south of the Bay of Bengal and around the south of Madagascar. The results show that the long life cycle MCSs are highly related to the colder brightness temperatures, less than 210 K and to enormous cloud cover surfaces greater than 105 km2. A study of the orientation of the movement in each MCS for various life durations indicates different preferential propagation directions of the MCSs in each subdivided zone; for example about 63% of the MCSs in the South of Madagascar go eastward. The second part of the study is to characterize the relationship between the regional precipitation with the MCSs distribution, the SSM/I data from three DMSP satellites have been used to estimate the rainfall. Rain rate over the ocean is derived and estimated from the Scattering Index algorithm by Grody [1991]. This result compares with the TRMM TMI rain rate estimations and Global Precipitation Climatology Project (GPCP) monthly and daily products. A monthly mean rain rate map shows the high correlation of higher rainfall with the higher frequency of MCSs distribution. The diurnal evolutions of precipitation show an obvious inclination of morning rain near the coastal areas but a non-preference over the open ocean. A final subject is considering the need of improvement in the data sampling during one day for a specific area in the tropical region. Comparing with DMSP and TRMM satellites which provide an average of one observation per day, the future Megha-Tropiques satellite will provide 3 to 6 observations per day for any point between 23°N to 23°S. This will be useful for the study of MCSs and the associated rainfall in different phases of their development.
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https://pastel.archives-ouvertes.fr/pastel-00002121
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Submitted on : Thursday, July 29, 2010 - 10:32:44 AM
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Taifeng Yang. Télédétection Multi-satellite des Propriétés des Systèmes Convectifs de l'Océan Indien ; Observation pendant la Mousson d'Hiver.. Physique [physics]. Ecole Polytechnique X, 2005. Français. ⟨pastel-00002121⟩

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