The impact of observed deforestation on the mesoscale distribution of rainfall and clouds in Amazonia

A numerical mesoscale model has been used to investigate the impact of meso scale circulations on the distribution of precipitation and cloudiness over a deforested area in Amazonia. Observed patterns of deforestation in Rondo nia, Amazonia, with scales on the order of 10 km were used in this study to describe land surface conditions. Various simulations have been performed to identify the conditions under which the mesoscale circulations induced b y the heterogeneous land surface could enhance cloudiness and local rainfal l. The simulation results suggest that the synoptic forcing, in terms of at mospheric stability and background horizontal wind, dominates during the ra iny season; synoptic conditions were so favorable to moist convection that the added effect of surface heterogeneity was negligible. During the dry se ason, a noticeable impact of mesoscale circulations resulting in enhancemen t of shallow clouds was simulated; the mesoscale circulations also triggere d scattered deep convection that altered the spatial distribution of precip itation. During the break period, the transition from the rainy season to t he dry season, the impact of mesoscale circulations on low-level clouds was evident only after reducing the magnitude of the background wind.