Direct radiative effects of tropospheric aerosols on changes of global surface soil moisture

A coupled modeling framework including a terrestrial ecosystem model and an atmospheric radiative transfer model is used to evaluate the aerosols’ direct radiative effects on the surface soil moisture in global terrestrial ecosystems during 2003–2010. We conduct two sets of model runs with and without aerosols in a hindcast mode. Comparison analysis indicates that the simulated soil moisture is comparable with other existing products and satellite retrievals. Simulations with aerosol loadings show an increase in the surface soil moisture by 3.8±0.4 % and 4.1±0.5 % during growing seasons (June to September) in temperate and boreal Northern Hemisphere (>10 °N) and the whole year in tropical regions (−10°S~10°N). This positive effect is as large as 30 % in dense-vegetated ecosystems, such as tropical forests and temperate broadleaf evergreen forests. The effect of aerosols on soil moisture varies with local leaf area index and climate, and exhibits seasonal variations. Surface soil moisture is persistently affected by high aerosols loadings in Amazonian tropical forests during drought seasons of 2005 and 2010. This study highlights the importance to consider the aerosols’ effects in impacting the soil moisture dynamics of the global terrestrial ecosystems.