Study on Southern Indian Ocean Dipole and the Spring Rainfall over the Middle and Lower Yangzte River

摘要

The spring rainfall in the middle and lower Yangtze river show obvious inter-annual and inter-decadal oscillation in recent 60 years. In positive southern Indian Ocean Dipole(PSIOD), the sea level pressure north the Mascarene is on the high side, so the cross equator flow enhance and abnormal cyclone appears the bay of Bengal. The water vapor flux in the southwest China enhances, and rainfall increase. The circulation pattern in negative southern Indian Ocean Dipole (NSIOD), just opposite in PSIOD, causes less rainfall in southwest and more rainfall in the Yangtze and the north of the eastern region. So all these indicates that the winter SIOD has certain instruction meaning to the spring rainfall in the middle and lower of Yangtze river.