1984-2017年ISCCP-FH辐射资料在青藏高原地区的适用性评估

Applicability Assessment of ISCCP-FH Radiation Product over the Tibetan Plateau During 1984-2017

长序列卫星辐射资料的缺乏一直是制约青藏高原(以下简称高原)辐射长期变化研究的重要原因之一。对国际上最新提供的1984—2017年ISCCP-FH(以下简称FH)长序列卫星辐射资料中的大气顶逸出长波辐射(OLR)、到达地面短波辐射(SWD)、地面向上长波辐射(LWU)、到达地面长波辐射(LWD)进行分析,评估了FH辐射资料在全天气条件下的青藏高原地区的适用性。结果表明:与观测相比,FH资料的4种辐射通量气候平均值误差均小于5%,其中OLR和SWD的偏差较小,LWU的偏差最大。FH资料能正确反映高原各辐射通量的冬季增强趋势,OLR和LWD在各季节的长期变化趋势均与观测一致,LWU则呈现虚假的减弱趋势。总体来说,在高原地区,FH资料的地面短波辐射通量比长波辐射通量适用性好。进一步对长波辐射偏差原因分析显示,气温偏差会增强LWD的气候态和长期趋势,而地温偏差对LWU的作用与之相反。辐射模型、云和水汽的差异导致最终FH资料中的LWD气候态和长期趋势较观测略偏弱,FH资料的计算方案在一定程度上修正了地温偏差造成的LWU偏弱。研究结果将为使用FH辐射资料提供参考依据。

The shortage of long-term satellite radiation products has restricted the study of radiation spatiotemporal variation over the Tibetan Plateau(TP).This paper presents evaluation of the state-of-the-art satellite products called ISCCP-FH(hereinafter to be refered as FH)over the TP.The all-sky OLR,downward shortwave radiation(SWD),upward longwave radiation(LWU)and downward longwave radiation(LWD)during 1984-2017 were compared with observation.The results indicate that the deviations of radiation flux climatology are within 5%,slight error exists in OLR and SWD while large bias is found in LWU.FH radiation fluxes are properly increasing in winter,the trends of OLR and LWD are consistent with observations in all four seasons but LWU weakens falsely.The FH shortwave radiation is generally better than longwave over the TP.The longwave radiation errors can be attributed to that air temperature error would overestimate LWD climatology and trend,and the influence of surface temperature on LWU is opposite.The radiation model,cloud and moisture differences may result in appreciable underestimation of LWD,while the calculation process of FH partly corrects the underestimation of LWU.This study would provide some references for the future use of FH products.