ESTIMATION OF SAHELIAN AEOLIAN DUST EMISSION BASED ON VEGETATION MODELING

摘要

The amount of dust emitted by wind from semi-arid regions is estimated with a large degree of uncertainty, mainly due to the difficulty in accounting for the effects of the seasonal vegetation. The temporal change of the vegetation has been investigated over the Sahelian belt (12°N to 20°N and 20°W to 35°E) from 2004 to 2007 with a daily time resolution. The seasonal vegetation was simulated using the STEP model (Sahelian Transpiration Evaporation and Productivity model; [1] ; [2] ) at scales of 0.1° and 0.25°. The simulations have been compared to the MODIS Leaf Area Indexes (LAI). The comparisons between the simulated vegetation fields and the MODIS LAI have been performed by examining the field structure, the dynamics of the vegetation growth, and the amount of vegetation. The agreement with satellite LAI is very satisfying during the active growth period, both in terms of structure and amount. The period of vegetation growth appears as very sensitive to the initialization parameters of the STEP model, which therefore have been carefully constrained. Based on these vegetation fields, Sahelian dust emissions are simulated and the influence of the seasonal vegetation is estimated.