Based on the variation of cloud fraction revealed by D2 Cloud Climatic Data of the InternationalSatellite Cloud Climatology Project and trend analysis methods, the trend of different types of cloud fractionover East Asia during 1984-2006 is obtained. The analysis focuses on the relationship between temperatureand different cloud fraction under the background of globe warming. The result shows a fluctuatingdecreasing tendency in the total cloud fraction, high-level cloud and low-level cloud over East Asia with thedecrement being 2.24%, 1.65% and 1.68%, respectively, while the mid-level cloud increases by 1.07%. Inaddition, there are great regional differences in cloud fraction. Temperature and water-vapor contentvariation caused by the greenhouse effects over East Asia is the primary reason for the variation of cloudfraction. Over the Tibetan Plateau, the Bay of Bengal and the Intertropical Convergence Zone, thetemperature is negatively correlated with high-level cloud, but positively correlated with mid- and low-levelcloud. However, over the West Pacific and the ocean east and north of Japan, the temperature is negativelycorrelated with low-level cloud but positively correlated with high-level cloud.
The results from some general circulation models show distinct radiative forcing(RF) by dust aerosol,which potentially has an effect on climate change.The direct RF and regional climatic effects of dust aerosol over the East Asian region are investigated in this study using NCAR's Community Atmospheric Model version 3.1.The negative RF at the top of the atmosphere(TOA) and the surface(SRF) has been revealed except for some high-albedo regions,which leads to a decrease in the surface air temperature and brings an increase of atmospheric radiative heating under both clear-and all-sky conditions.The decrease in the surface air temperature can be found over a wide region that includes the Indian peninsula and northwest China.It accompanies an increase in eastern China and the Korean peninsula,and temperature changes are not limited to regions with a large dust optical depth.A belt of vapor increase is revealed from the Indian peninsula extending east to northern China,while vapor content evidently deceases in southwest China.An increase in precipitation can also be found in the belt of increased vapor accompanying the reduction of precipitation across the regions to the south of 30oN.The pattern of rainfall change helps to offset the trend of increasing wetness in the south and increasing dryness in the north of China in recent years.
