Effects of total aerosol on temperature and precipitation in East Asia

Numerical simulations were conducted for 1960-2000 to estimate the direct effects of aerosols on temperature and precipitation in East Asia. Radiative forcing and regional climatic effects of total combined aerosol-including sulfate, dust, black carbon, and organic carbon-over the East Asian region were investigated using the NCAR Community Atmospheric Model, Version 3.1. Surface dimming is revealed by the simulated negative radiative forcing at the surface, and the most distinct dimming can exceed 30 and 25 W m(-2) under clear and all sky conditions, respectively; dimming cools the surface by 1.5 K in most regions in the study domain. Air column temperatures increase in northern India and northwestern and northern China, and decrease in other areas. The profiles of air temperature show similar trends in different areas, with a decrease below 850 hPa and an increase in the middle of the troposphere. The finding of increases in vapor content and precipitation in northern and northwestern China contradicts recent trends of flooding in the south and drought in the north of China, which have been attributed to the effects of aerosol absorption in some simulation studies. In our study, significant precipitation increases by a maximum of 9 % in northern and northwestern China, while it decreases by up to 12 % in the southern part of the Tibetan Plateau, the Sichuan Basin, and most of southern, southeastern, and northeastern China.