EFFECTS OF WESTERLY WIND BURSTS UPON THE WESTERN EQUATORIAL PACIFIC-OCEAN, FEBRUARY-APRIL 1991

In February-April 199 1, episodes of 2 to 8 m s - 1 westerly winds of 3 to 11 days' duration occurred in the western Pacific warm pool. Resulting modifications of the upper ocean in current and hydrology are quantified using data from an equatorial mooring at 165-degrees-E and from three cruises within 30 days of one another along 165-degrees-E. During westerly wind bursts (WWB) stronger than 4 m s - 1, the upper 50 m becomes isothermal to within 0. 1-degrees-C and sea surface temperature (SST) drops by 0.3-0.4-degrees-C between 5-degrees-S and 2.5-degrees-N. Conversely, SST starts warming and the upper 50 m restratifies in 4-5 days after the end of WWB. In contrast to previous observations, salinity between 0 and 50 m appears almost unaffected by WWB; it freshens by 0.4 practical salinity unit in March within an area of 1-degrees-2-degrees of latitude around the equator but not necessarily in direct response to WWB. As for zonal circulation, surface equatorial flow accelerates eastward 2-3 days after the beginning of westerlies. Then, after less than 2 weeks, eastward and westward jets both develop from 2-degrees-N to 2-degrees-S in the upper and lower halves of the temperature mixed layer, respectively. Changes in zonal mass transport in this layer were as much as 30 Sv between 2.5-degrees-S and 2.5-degrees-N from one cruise to the next.