Analysis on Temporal and Spatial Variations for Cloud Radiation Forcing over Qinghai-Xizang Plateau Using CERES(SYN) Data

The cloud and radiation data,archived in CERES(Clouds and the Earth′s Radiant Energy System) SYN(Synoptic Radiation Fluxes and Clouds) product,are applied to gain a better understanding of the temporal and spatial variations of cloud radiation forcing over the Qinghai-Xizang Plateau(QXP) from November 2001 to October 2005.The results indicate four important points: Firstly,the whole QXP is the transition area of cloud radiation forcing,and this transition has significant seasonal and regional variations.The southeast of QXP makes a cooling effect,the western and northeastern QXP regions,an arid area,showed a weaker warming effect.Secondly,high cloud,upper-middle cloud and lower-middle clouds all contribute to the seasonal and regional differences of cloud shortwave radiation forcing,and the middle cloud is the main factor of regional differences;regional differences of longwave radiation forcing is not so obvious,but it has significant seasonal difference,which is mainly caused by the high cloud and upper-middle clouds,and cloud amount is a main factor of influence.Although the cloud amount of high cloud is small,but its impact is unnegligible.Thirdly,over QXP,high cloud causes a net heating effect,upper-middle clouds have both heating effect and cooling effect,and low cloud cause a net cooling effect.Fourthly,for the diurnal variation of cloud radiation forcing,the shortwave plays a dominating role.The significant regional differences of diurnal variation are mainly caused by the cloud amount.During the daytime,the lower-middle clouds have the greatest contribution on the diurnal variation of shortwave radiation.At night,the high cloud plays an important role of diurnal variation of shortwave radiation,while the lower-middle clouds inhibit the for longwave radiation forcing.