southeast wind
4.The cold air could reach low latitude area when the stable meridional circulation pattern controls the Southern Hemisphere. The strong southeast wind to the north of lower layer cold high located behind the long wave trough could form a strong and persistent cross-equator flow in a relatively fixed narrow channel. In some favorable conditions of Northern Hemisphere circulation, this cross-equator flow could turn into southwest flow over the Northwest Pacific and lead to intensification of southwest monsoon.
6.The rsults are as follows: (1) precipitation shows the decreasing trend and remarkable interannual and interdecadal variations in flood season in the last 44 years. (2) precipitation anomalies in flood season have a good correlations with southwest and southeast summer monsoon, polar vortex, west wind trough, the subtropical high over West Pacific and South Asia High.
