West African Monsoon And Satellite Observations Of Water Vapor
The atmospheric water vapor, a main climatic parameter, remains also one of the less well known in the inter tropical area. Different space programs have been carried out to improve its measure: the data provided by these experimental or operational programs, give an alternate and complementary information the model’s analysis. Moreover, the time series available today, are long enough to allow studies of variability of different climatic parameters. The following contribution, dedicated to the climate of the Western Africa, analyses the atmospheric humidity as retrieved by NOAA8/TOVS12 dated over the last 20 years. The climatology of the upper tropospheric humidity (UTH13), retrieved from HIRS-121, evidences the importance of the position and the "strength" of dynamic component such as convergence zone, subtropical high: the relative position and the intensity of the subsidence linked to the St-Helena anticyclone appear as a key parameters for the quality of the sahelian rainfall season. Moreover, the integrated water vapor content over the Gulf of Guinea, as extracted from the NVAP9 data base (blended satellite and radiosondes observations) indicates that water vapor changes slowly; its inertia may be used for trend analysis : excess or deficit of water vapor coincides with wet or dry rainy season over the Sahel. Computations of water vapor fluxes for the lower levels (coupling the TOVS humidity to NCEP7 winds), precise the localization of the monsoon fluxes entry over the western Africa .
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