Indian Ocean subtropical dipole and variations of global circulations and rainfall in China

Based on the observed data during the period of 1951~2001,the effects of the subtropical dipole of SST in the southern Indian Ocean(IOSD)on the global 500 hPa circulations and the rainfall in China are investigated.Results show that the low frequency wavetrain of circum-Pacific pattern(CP)exists over Pacific Ocean for the extreme phase of IOSD in the Northern Hemisphere winter,in which the main periods are about 2.0 and 6.5 a,and is closely linked to SST in the equatorial central and eastern Pacific.The Eurasian Pacific pattern(EUP)and the central Pacific/the North Pole(CPNP)wavet rain in the Northern Hemisphere and southwestern Pacifict eleconnection pattern(SWP)in the Southern Hemisphere are dominant for the following spring.When there is a pattern with west negative and east positive in the subt ropical southern Indian Ocean in winter,the negative EUP pattern is stronger during the next spring,leading to a weak trough in eastern Asia and plenty rainfall in north of Changjiang River Valley,in particular the upper and middle reaches of Huanghe River Valley.Conversely,the stronger and stable trough in East Asia,resulting in the rare rainfall in east China.It is reflected the connections between the interactions of air-ocean system in the southern Indian ocean and low frequency variations in the tropical and extratropical eastern Asia.Thus,the intensity of IOSD in the Northern Hemisphere winter is considered as one of the main factor for the predicting of the rainfall in the north of China in the following spring.