Interdecadal Variation Of Spring Land-Ocean Thermal Key Areas Affecting East Asian Summer Monsoon

By using the monthly mean SST data from HadISST, ERA40 reanalysis data, NCEP/NCAR reanalysis data and the data of weather stations in China, the characteristic of variation in global surface thermal conditions in spring, and its impacts on the interdecadal variation of the East Asian Summer Monsoon have been investigated. Further, the interdecadal variation of the spring land-ocean thermal key area affecting the Monsoon is discussed. The results showed that:(1) The interannual variability of sea surface temperature in the North Pacific, eastern equatorial Pacific and South Pacific is larger than in other regions. The sea surface temperature in most parts of the world has shown warming trends except the North Pacific and the part of South Pacific. The inter-annual variability of land surface temperature in high latitude regions of the Northern Hemisphere is larger than that in other regions. The significant warming regions are mainly located in the high latitudes of Eurasia. It can be found that the global conditions described by the ERA40 reanalysis and the NCEP/NCAR reanalysis data are largely resemble in African and Eurasian continent by the comparative analysis on the climatology, standard deviation, spatial and temporal distribution, and long-term trends of it. The ERA40 reanalysis, the NCEP/NCAR reanalysis data and the surface temperature data of weather stations in China were comparatively analyzed, which indicated that the surface temperature of ERA40 reanalysis data is more coincidence with observations.(2) In spring, the thermal conditions of Northern Eurasia, Southern Eurasia, eastern equatorial Pacific, western equatorial Pacific and the South Pacific have significant impacts on the East Asian Summer Monsoon. When the surface temperature of the Northern Eurasia, the western equatorial Pacific and the South Pacific is negative (positive) anomalies, while the surface temperature of the southern part of Eurasia and the eastern equatorial Pacific is positive (negative) anomaly, the East Asian Summer Monsoon is stronger (weaker).(3) There is a significant interdecadal variation in the impact of land-ocean thermal conditions in spring on the monsoon. Before the late of 1970s, key areas are located in southeast of Eurasia and the eastern equatorial Pacific. When the surface temperature of the southern part of Eurasia and the equatorial eastern Pacific is positive (negative) anomaly, the East Asian Summer Monsoon is stronger (weaker). After the late of 1970s, key areas are lies in Northern Eurasia, the western equatorial Pacific and the South Pacific. When the surface temperature of the Northern Eurasia, the western equatorial Pacific and the South Pacific is negative (positive) anomalies, the East Asian Summer Monsoon is stronger (weaker). The heat index defined by different thermal conditions of the key areas can respectively reflect the interannual and interdecadal variations of monsoon before and after the late of 1970s.