How does local tropical deforestation affect rainfall?

Abstract

The aim of this study is to investigate the potential impacts of vegetation-breezes on locally-generated rainfall and its distribution on the mesoscale. Ensembles of simulations with a 2D large-eddy model were performed using various heterogeneous land surfaces. Rainfall was found to be 4-6 times higher over warmer surface anomalies, associated with cropland, compared to a homogeneous surface, but rainfall was reduced to half or less over the forest. While the suppression of rainfall tended to occur throughout the forest with an intensity comparable to the surface anomaly, the exact location of the maximum in rainfall was less predictable. The location of peak rainfall depended on an interplay between the size of the heat flux gradient (governing the vegetation-breeze strength), the size of the anomaly (as vegetation-breezes organize in certain preferential length-scales), and the distance to other anomalies (since convection in one location could suppress it elsewhere). The presence of surface heterogeneity also increased the total rainfall in the domain by 13% on average, with higher increases in the presence of more intense surface variabilities. Copyright 2011 by the American Geophysical Union.