Shortwave absorption properties of atmosphere over China

The absorption of shortwave radiation in the atmosphere was investigated by using ISCCP-FD monthly data and quality-controlled pyranometer monthly data in China for the period from 1984 to 1999. The net shortwave radiation at the top of the atmosphere was evaluated from ISCCP-FD data, while that at the surface was evaluated from pyranometer data of Chinese Meteorological Administration with ISCCP surface albedo values. The absorptance of the atmosphere was obtained by normalizing with solar insolation at the top of the atmosphere. The results obtained from 44 locations are as follows. The absorptance of the atmosphere over China is 27.1% which is larger than that estimated to be global average of 20%, and becomes up to 40% in several locations. The large abosorptance is found in the central, east and southeast regions of China. The absorptance in the north and northeast regions of China has a maximum in spring or summer season, while that in the central region, particularly in the Sichuan basin, has a maximum in winter season. The absorption properties in the latter region might be attributed to absorbing aerosols. Clouds, in general, do not affect the shortwave absorptance so much while aerosols as well as water vapor affect it particularly in small cloud amount cases and in the high latitude regions in winter where optical path of direct solar radiation is large.