利用CERES(SYN)资料分析青藏高原云辐射强迫的时空变化

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

利用2001年11月—2005年10月"云与地球辐射能量系统(CERES)"辐射和云资料SYN(Syn-optic Radiation Fluxes and Clouds),分析了青藏高原(下称高原)地区不同高度云辐射强迫的时空变化特征。结果表明:(1)高原整体为云强迫正、负值的过渡区域,这种过渡性有显著的季节差异和区域划分。高原东南部表现出较强的冷却效应,其西部和东北部干旱区在冬、春季表现为较弱的加热效应。(2)高云、高的中云和低的中云对云短波辐射强迫的季节变化都有贡献,其中中云是导致区域差异的主要因素;云长波辐射强迫的区域差异不明显,但季节差异显著,这主要是由高的中云和高云的变化引起的,且云量是主要的影响因子,高云云量虽小但其影响不可忽视。(3)高云在高原地区产生净加热效应,高的中云既产生加热作用也产生冷却作用,低的中云产生净冷却效应。(4)云短波辐射强迫在云辐射强迫的日变化中仍然占主导地位,日变化的区域差异主要是由云量引起的。白天,在云短波辐射强迫的日变化中,低的中云贡献更大。高云对云长波辐射强迫的日变化贡献主要在晚上,低的中云在夜间对云长波辐射强迫有抑制作用。

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.