A 247-km path length sound transmission experiment using a single sound source sending to a remote receiver was performed during February--June 1992 along the latitudinal line of 10 ¿N in the North Equatorial Current off Mindanao Island, Philippines. The range-averaged temperature was reconstructed at three layers (65--500 m, 500--1500 m, and 1500--3300 m) through the inverse analysis of travel time data obtained between the source and receiver. The temperature remained nearly constant during February--March and increased by 0.8 ¿C for the upper and middle layers and 0.2 ¿C for the lower layer in the subsequent months. A 0.8 ¿C temperature increase was in good agreement with expendable bathythermograph results obtained at the start and finish of the experiment. National Oceanic and Atmospheric Administration advanced very high resolution radiometer images also show evidence of a warming of the surface water by 2.0 ¿C during the same period. It is concluded that this acoustic experiment observed a warm event which took place in the western equatorial Pacific with the decay of the 1991--1992 El Ni¿o. ¿ American Geophysical Union 1996