Atmospheric feedbacks of LULC change on hydrometeorological aridity in regions of complex terrain in South America

Moisture transport associated with human induced vegetation change over complex terrain in South America was investigated using the Weather Research and Forecasting (WRF) model for three characteristic hydrometeorological regimes during the monsoon and dry season. The simulations show that conversion of savanna to cropland and woodland mixture over the Brazilian Cerrado in the dry season leads to an increase of moisture leaving the region, thus amplifying and reinforcing dry conditions. This is due to the development of a low-level low-pressure perturbation in the neighboring Amazon, which is established by the advection of colder upstream air. The enhanced moisture transport is stronger at night than during the daytime. During the monsoon, however, the impact of vegetation conversion on low-level thermodynamics is attenuated by reduced evaporative cooling. Implications of this aridity enhancement mechanism for regional climate are discussed using the NCEP-FNL reanalysis and TRMM precipitation observations.