Variation Characteristics Of Spring And Summer Land Surface Thermal Anomalies Over Eurasian Continent And Its Relationship With East Asian Summer Monsoon

Based on NCEP, JRA-55, CRU reanalysis data(1961-2010), We research the variation of Spring and Summer surface air temperature in Eurasia,and interannual, decadal changes of EASM, besides,discuss the relation between them. Result suggest that:(1) Spring temperature in Eurasia decreases gradually from the equator to north latitude. Isotherm is parallel with latitude. The entire continent basically shows warming trend, small area in south continent shows cooling trend. The trend of warming in Northern area is greater than in Southern area. Surface air temperature reflects an out-of-phase variation across the Eurasian continent. Time Series shows decadal turn around.(2) Summer temperature in Eurasia distribution consistent with the spring’s and shows warming trends. Temporal and spatial distribution characters the entire Eurasia region is negative, and two positive area in Southwest small area.Time Series shows decadal turn around.(3) EASM divided into two categories:There is obvious decadal variation for first EASMI> which reflects a consistency variation of EASM and correspond to the first mode of EASM. Correspondingly, for the positive EASMI,There is a whole stronger summer monsoon in entire East Asian; There is significantly increased rainfall in Northern and Northeast China and reduced rainfall in Yangtze River and its southern area. There is interannual variation for second EASMI, which reflects an out-of-phase variation of EASM and correspond to the second mode of EASM. When the EASMI is in positive phase, there is a weaker summer monsoon in Southeast China and a stronger summer monsoon in Northeast China; There is increased rainfall in Inner Mongolia, Northeast, South China and reduced rainfall around Yangtze River,This pattern for rainfall consist of Three-pole type monsoon rainfall.(4) Eurasia spring surface temperature connects well with the first class EASMI,Thermal key region is:Eurasia northeast region,Tibet Plateau region,we can use coefficient of first mode to represent Thermal Index T1. When T1 is positive, air column in Northern Eurasia is cold,which result the near ground controlled by a low pressure center, so, entire East Asia is controlled by the southerly flow,which is affected the cyclone.(5) Eurasia summer surface temperature connects well with the two class EASMI,Thermal key region related with second EASMI is:Left area of the Sea of Okhotsk. When T2 is negative, air column in Left area of the Sea of Okhotsk is cold, which result the near ground controlled by a low pressure center,and it will be beneficial for subtropical high to northward. So south China is controlled by the southerly flow,which is affected the subtropical high.