The Variation Characteristics Of Solar Radiation In Recent 43 Years And Research On Cloud Optical Properties

The energy of atmospheric motion mostly comes from solar radiation. By usingreal-time solar radiation and scattered radiation data at the four stations of Beijing,Guangzhou, Shenyang and Wuhan from 1961 to 2003, statistical analyses show thatthe total solar radiation and direct radiation gradually decrease in recent 43 years,and both have positive departure before 1980s by contrast to negative departure after1980s. However, the scattered radiation does not decrease prominently, and even hasan increasing trend in Guangzhou and Shenyang. This indicates that the variation oftotal solar radiation is mainly caused by direct radiation. Further study proves thatthe variation tendencies of percentage of sunshine and total radiation are consistent,while the total radiation is negatively correlated with the average air temperature andprecipitation. We also explain that it is the cloud that determines the income andexpense of radiation received by surface.The cloud optical depth is one of the important microphysical characteristics.Based on the radiative transfer theory, this paper analyses the relationships amongthe reflectivity measured by satellite, cloud optical depth, phase function, solar zenithangle and ground albedo, and also investigates the effect of different ground albedoson the satellite measurement, to reveal the feasibility of cloud optical depth retrievalby using satellite data. The results show that the cloud optical depth is correspondingto the reflectivity measured by satellite for thin cloud. The cloud optical depth isretrieved by using the GMS-5 satellite data from August to October in 2003. Theresult is compared with the data get from the ground radiation data during thecorresponding period with satellite in Shanghai. The two results are approached toeach other. So we may use the high spatial and temporal resolution of satellite, tocarry on the wide range radiation observation and the cloud layer, the aerosol opticalcharacteristic monitoring, making up the ground survey station scarce insufficiency.