Interannual Fluctuations of the Tropical Pacific Wind Field and the Southern Oscillation

Abstract

Linear regression analysis of tropical Pacific winds versus a Southern Oscillation Index (SOI) show departures from the seasonal mean wind associated with the phase of SOI. When the SOI is low the largest departures are westerlies on the equator and in the subtropics west of the dateline. The Intertropical Convergence Zone (ITCZ) and the South Pacific Convergence Zone (SPCZ) shift equatorward. Departures from mean wind are strongest from September through February and weakest from March to May. The usual pattern of cyclonic wind stress curl in the tropics and anticyclonic wind stress curl in the subtropics intensifies when the SOI is low. Effects of these changes on ocean circulation are discussed and compared to changes in ocean circulation data.