INDEX OF LAND-SEA THERMAL DIFFERENCE AND ITS RELATION TO INTERANNUAL VARIATION OF SUMMER CIRCULATION AND RAINFALL OVER EAST ASIAN
Sun Xiurong (Shanghai Typhoon Institute,Shanghai 200030) Chen Longxun (Chinese Academy of Meteorological Sciences,Beijing 100081) He Jinhai (Department of Atmospheric Science,Nanjing Institute of Meteorology, Nanjing 210044)
An index of land sea thermal difference ( I LSTD ) has been designed to study its relation to the variation of East Asian monsoon circulation in summer.The results are as follows:(1) I LSTD can be used to identify the strength of East Asian summer monsoon.The years of strong(weak) I LSTD are associated with stronger(weaker)summer monsoon circulation.(2)The index also can reflect summer rainfall anomaly over eastern China.In the years of strong I LSTD ,rainfall belt is mainly located over northern China,and obvious drought emerges in Huaihe River valleys and the mid-lower reaches of Yangtze River.However,during the weak years,summer monsoon is weak and summer rainfall belt is located over the mid-lower reaches of Yangtze River.The circulation fields of strong (weak)index years can explain the features of rainfall anomaly.(3)Besides,the I LSTD has obviously QBO and quasi-4-year and interdecadal oscillations.