OBSERVATION OF LARGE DIURNAL WARMING EVENTS IN THE NEAR-SURFACE LAYEROF THE WESTERN EQUATORIAL PACIFIC WARM POOL

Because of the relatively calm winds which prevail over the western Pa cific warm pool, the diurnal cycle of temperature in the near-surface layer of the ocean is often guile pronounced. During the TOGA Coupled Ocean-Atmosphere Response Experiment (COARE), very high resolution mea surements of near-surface thermohaline and turbulence structures were made using bow-mounted probes and a free-rising profiler. Experimental data demonstrate a strong dependence of near-surface thermal structur e on weather conditions. In calm weather, SST was observed to exceed 3 3.25 degrees C; this was associated with a diurnal warming of more tha n 3 degrees C in the top 1 m of the ocean. A 1-D model of transilient type reproduces the diurnal cycle at low wind speeds and the evening d eepening of the diurnal thermocline. Precipitation influenced the diur nal cycle by trapping hear in the near-surface region. During daytime evaporation, surface salinity increased slightly, but deep convection was inhibited by the strong vertical temperature gradient. Contour plo ts calculated using observations from bow sensors ''scanning'' the upp er meters of the ocean due to ship's pitching in some cases revealed s trong horizontal variability of the shallow diurnal thermocline with a mplitude similar to 2 degrees C on scales of 0.2-6 km. (C) 1997 Elsevi er Science Ltd.