The Relationship of Land-Ocean Thermal Anomaly Difference with Mei-yu and South China Sea Summer Monsoon

Based on the NCEP/NCAR reanalysis data for the period of 1948--2004 and the monthly rainfalldata at 160 stations in China from 1951 to 2004, the relationships among the land-ocean temperatureanomaly difference in the mid-lower troposphere in spring (April--May), the mei-yu rainfall in theYangtze River-Huaihe River basin, and the activities of the South China Sea summer monsoon (SCSSM) areanalyzed by using correlation and composite analyses. Results show that a significant positive correlationexists between mei-yu rainfall and air temperature in the middle latitudes above the western Pacific,while a significant negative correlation is located to the southwest of the Baikal Lake. When theland-ocean thermal anomaly difference is stronger in spring, the western Pacific subtropical high (WPSH)will be weaker and retreat eastward in summer (June--July), and the SCSSM will be stronger and advancefurther north, resulting in deficient moisture along the mei-yu front and below-normal precipitation inthe mid and lower reaches of the Yangtze River, and vice versa for the weaker difference case. Theeffects and relative importance of the land and ocean anomalous heating on monsoon variability is alsocompared. It is found that the land and ocean thermal anomalies are both closely related to the summercirculation and mei-yu rainfall and SCSSM intensity, whereas the land heating anomaly is more importantthan ocean heating in changing the land-ocean thermal contrast and hence the summer monsoon intensity.