The Study Of The Tropical Indian-Pacific Ocean Thermodynamic Anomaly Joint Mode And The Impact Of This Mode On The Summer Rainfall Over China

Tropic Pacific Ocean and Indian Ocean both have important impacts on the summer rainfall over China. Because the variability of the temperature in those two oceans have a relationship with each other, so it would be of important theoretic and practical significance if the pacific ocean and Indian ocean were seen as a whole , the spatial and temporal thermodynamic variation characters of them was studied , the joint mode index was given ,which could represent the basic characters of the thermodynamic variation for the two oceans, and the impacts of this mode on the summer rainfall over China were discussed.Based on the monthly mean heat content data in the global ocean, SODA data, the monthly mean precipitation data at 160 observational stations of China ,the 850hPa zonal wind data of NCEP\NCAR and the Western Pacific Subtropical High index during 1955 to 2003, using the empirical orthogonal function (EOF) and canonical correlation analysis ,the spatial and temporal variation characters of heat content anomaly field in the tropical Pacific Ocean and Indian Ocean were analyzed and the Tropical Indian-Pacific Ocean thermodynamic anomaly joint mode index was given, and the reasons of this joint mode's variability and the impacts of this joint mode on the summer rainfall over China were also discussed in this paper. The results showed as followed. Firstly, the Tropical Indian-Pacific Ocean thermodynamic anomaly joint mode not only had distinct interannual and interdecadal variations, but also jumped from cold to warm in 1976. And there were close relationships between this mode and ENSO and Indian dipole, indicating that this model could represent the basic characters of ENSO and Indian Dipole synchronously.Secondly, the interdecadal variability in the Indian-Pacifica joint mode had close relationships with the zonal migration of the western Pacific warm pool and the 850hPa zonal wind anomaly over the central equatorial Pacific, but the zonal migration of two warm pools and the zonal wind anomalies over the central equatorial Pacific and the eastern equatorial Indian Ocean were all responsible for the interannual variability of the Indian-Pacifica joint mode.Finally, the joint mode had an important influence on the summer rainfall over China with a time-lead of half year especially in winter. The impacts of the joint mode on the summer rainfall over China were possibly made through the variation of the summer Western Pacific Subtropical High.