The Impact of El Nino Event on Tropical Circulation

Using the tropical grid wind data and OLR data set of NMC for 17 years, we have compared the tropical circulation of typical El Nino year with that of the La Nina year. It is found that in El Nino year the strongest convective region which is climatologically located in the equatorial western Pacific is weakened and moved eastward to the central Pacific, and the east—west heating gradient becomes smaller. Therefore, both the Walker circulation over the central—eastern Pacific and the anti-Walker circulation over the western Pacific and Indian Ocean would be weakened. Meanwhile, the El Nino event would also weaken the anti-Hadley circulation over the central and eastern Pacific and Hadley circulation over the American continent