Regional modelling of rainfall erosivity: sensitivity of soil erosion to aerosol emissions

Abstract

A rainfall erosivity scheme is implemented into the widely used regional atmosphere-land model, WRF. Rainfall erosivity is parametrized from hourly precipitation and surface runoff in a high resolution (4 km) convection-permitting model. The scheme is used to examine the potential effects of changes in atmospheric aerosol concentrations on soil erosion in a case-study of northern India and the surrounding countries for the 2010 monsoon season, using a model which isolates the indirect effect on cloud microphysics only. This study offers a preliminary investigation into this emerging topic, but longer simulations would be needed to establish a robust signal.Summer precipitation is reduced in most areas and the monsoon circulation weakens for increases in cloud condensation nuclei concentrations. This can be attributed to localised cloud microphysical changes in the northeast of India, which induce a dynamic response opposing the monsoon circulation. The two regions of greatest decrease in erosion with increasing aerosol are in the Western Ghats and the Ganges Delta, both significant cropland areas. However, the effect is not uniform, with isolated local increases in soil erosion. These results suggest that, while efforts to reduce anthropogenic aerosol emissions may improve water availability for crops through enhanced rainfall, these benefits are likely to be tempered by an increase in soil erosion, though robust local changes were difficult to predict.