青藏高原前期冬春季地面热源与我国夏季降水关系的初步分析

首先对青藏高原地表热通量再分析资料与自动气象站(AWS)实测资料进行对比, 结果表明: 相对于美国国家环境预报中心和国家大气中心20世纪90年代研制的NCEP/NCAR(Kalnay 等1996)和NCEP/DOE (Kanamitsu 等2002) 再分析资料, ECMWF(Uppala 等2004)资料在高原地区的地表热通量具有较好的代表性。进一步利用奇异值分解(SVD)方法分析了ECMWF资料反映的高原地面热源与我国夏季降水的关系, 发现前期青藏高原主体的冬季地面热源与长江中下游地区夏季降水量呈负相关, 与华北和东南沿海地区的夏季降水量呈正相关。而长江中下游地区夏季降水量还与春季高原南部的地面热源存在负相关、与高原北部的地面热源存在正相关。高原冬、春季地面热源场的变化是影响我国夏季降水的重要因子。

The Preliminary Analysis of the Relationships between the Surface Heat Source over the Tibetan Plateau in Winter and Spring and the Summer Rainfall over China

It is well known that the thermal effects of the Tibetan Plateau play an import role in the general circulation of atmosphere and climate in East Asian,even in the global world.The reanalysis data can server as a beneficial supplement to research the thermal effects of the Tibetan Plateau.There are few researches on the relationships between the summer rainfall over China and the surface heat source over the Tibetan Plateau through the use of the surface heat fluxes of reanalysis data.However,there is a doubt about the reliability of the surface heat fluxes of the reanalysis data over the Tibetan Plateau.Therefore,the surface fluxes of sensible heat and latent heat for the three sets of reanalysis data of NCEP/NCAR(NCEP1),NCEP/DOE(NCEP2),and ECMWF(ERA) are compared with those of Automatic Weather Station(AWS) data over the Tibetan Plateau under the China-Japan cooperation research project on the Asian monsoon mechanism and the Global Energy and Water Balance Experiment-Tibetan Monsoon Experiment(GAME/Tibet).The results show that the variation trends of both daily and monthly surface heat fluxes of reanalysis data are basically in accordance with those of AWS data.The surface heat fluxes of ERA data have better representations compared to those of NCEP1 data and NCEP2 data,especially for the sensible heat flux in western Tibetan Plateau.The sensible heat flux of ERA data can also show the interannual change of the sensible heat flux of AWS data.On the basis of the above,the relationships between surface heat source over the Tibetan Plateau with ERA data and the summer rainfall in China are investigated with singular value decomposition(SVD) method.It is found that the previous surface heat source over the plateau region in winter is negatively correlated with the summer rainfall over the mid-lower reaches of the Yangtze River,and positively correlated with rainfall in North China and the coast of southeastern China.And the summer rainfall in the mid-lower reaches of the Yangtze River also has negative correlation with the surface heat source over the southern plateau and positive correlation with the surface heat source over the northern plateau in spring,with the distinctive correlation areas in the Karakorum Mountain and the Nyainqentanglha Mountains.The surface heat sources over the Tibetan Plateau in both winter and spring are important influence factors on the summer rainfall in China.The long-term trends of surface heat sources over the Tibetan Plateau in winter and spring are both in accordance with the interdecadal variation of snow cover over the Tibetan Plateau,and their effects on the summer rainfall in China can be confirmed well by each other.