Numerical Study of the Effect of Anthropogenic Aerosols on Spring Persistent Rain over Eastern China

The effect of anthropogenic aerosols on the spring persistent rain (SPR) over eastern China is investigated by using a high-resolution Community Atmosphere Model version 5.1 (CAM5.1). The results show that the SPR starts later due to anthropogenic aerosols, with a shortened duration and reduced rainfall amount. A reduction in air temperature over the low latitudes in East Asia is linked to anthropogenic aerosols; so is a weakened southwesterly on the north side of the subtropical high. Meanwhile, air temperature increases significantly over the high latitudes. This north-south asymmetrical thermal effect acts to reduce the meridional temperature gradient, weakening the upper-level westerly jet over East Asia and the vertical motion over southeastern China. As a result, the SPR is reduced and has a much shorter duration. The indirect effect of anthropogenic aerosols also plays an important role in changing the SPR. Cloud droplet number concentration increases due to anthropogenic aerosols acting as cloud condensation nuclei, leading to a reduction in cloud effective radius over eastern China and a reduced precipitation efficiency there.