Abnormal Characteristics Of Differences Between Ground And Air Temperature In Spring And Its Impact On Precipitation In Eastern China

T_s-T_a is direct correlated with sensible heat in spring,it could represent the special and temporal characteristics of sensible heat in some extent.Furthermore,it is one of the important impact factors for the heat condition on land.This paper is based on the ocean-land thermal difference,the significant reason of summer monsoon onset.By using the station and NCEP data,with many statistic methods,such as synthetical method,correlation analysis,empirical orthogonal function(EOF)and singular value decomposition(SVD),we research and discuss the Chinese T_s-T_a abnormal distribution is spring from 1957 to 2006.In addition,the influence of altitude on the T_s-T_a is analyzed.And it is studied that T_s-T_a in spring has impacts on summer precipitation in Eastern China especially Middle-Lower reaches of Yangtze River.Moreover,we discuss the correlation between T_s-T-a in spring on Tibetan Plateau and moisture transport in summer.The results show as follows:The distribution of T_s-T_a is similar to physiognomy,and they are both higher in western China than eastern China.Actually,the values of them are both the highest over Tibetan Plateau.The correlation analysis indicates that T_s-T_a in spring over most part of China plateau has obvious influences on the summer precipitation in Yangtze-Huaihe River Valley.It is said that higher T_s-T_a in spring over most part of China plateau leads to the more summer precipitation in Yangtze-Huaihe River Valley.Regional average T_s-T_a over the areas higher than 1000m,2000m and 3000m which are unimodal distributed reach the top in late spring-early summer and the lowest points at December.The correlation coefficients between T_s-T_a and altitudes is bimodal from January to December.And at spring and autumn,it comes to the highest points.By means of the correlation analysis,EOF and SVD,we conclude that T_s-T_a in spring over Tibetan Plateau is direct correlated with summer precipitation in Middle-Lower reaches of Yangtze River.When it is drought in Middle-Lower reaches of Yangtze River,the high-value of T_s-T_a is moving towards east with time process.The T_s-T_a in spring over Tibet Plateau is stronger(weaker)while the summer precipitation in Middle-Lower reaches of Yangtze River is more(less),so The T_s-T_a in spring over Tibet Plateau is the strong 'precursory signal' for the summer precipitation in Middle-Lower reaches of Yangtze River.It is 'south- negative and north-positive' that the first EOF eigenvector's distribution of the departure of T_s-T_a in spring over China,and it is available for the east Asia summer monsoon's weakening after 80s,20^thcentury.It is helpful for the convergence of summer moisture transport in Middle-Lower reaches of Yangtze that high T_s-T_a in spring over Tibetan Plateau and low in Huanghuai area.