Toward reconciling the influence of atmospheric aerosols and greenhouse gases on light precipitation changes in Eastern China

The attribution of the observed shift in precipitation extremes to different forcing agents represents a critical issue for understanding changes in the hydrological cycle. To compare the effects of aerosols and greenhouse gases on the historical trends of precipitation intensity, we have performed the National Center for Atmospheric Research/Department of Energy Community Atmosphere Model version 5.3 (CAM5) model simulations from 1950 to 2005 driven by observed sea surface temperature and sea ice with and without anthropogenic aerosol forcings. Precipitation rates at every model time step in CAM5 are used to construct precipitation intensity probability distribution functions. We found that the accumulation of greenhouse gases is responsible for the shifts in precipitation intensity on the global scale. However, in Eastern China, dramatic increases in anthropogenic aerosols appear to account for most of the observed light precipitation suppression since 1950s. Under the warming climate induced by greenhouse gases, the enhanced ascending motions primarily lead to the decreases in light precipitation frequency and increases in moderate and heavy precipitation frequencies over the tropics, but there is no significant change in ascending motions in Eastern China only due to the greenhouse gas forcing. By modifying cloud microphysical properties and warm rain processes, aerosol microphysical effects dominate over aerosol radiative effects in determining the historical trend of precipitation intensity distribution in Eastern China.