CLOUDS, RADIATION, AND THE DIURNAL CYCLE OF SEA-SURFACE TEMPERATURE IN THE TROPICAL WESTERN PACIFIC

The relationship among clouds, surface radiation flux, and the sea sur face temperature (SST) of the tropical western Pacific Ocean over the diurnal cycle is addressed in the context of the Atmospheric Radiation Measurement (ARM) Program scientific objectives for the tropical west ern Pacific Ocean. An understanding of the relationship between clouds and SST on a variety of time and space scales is needed to understand fully the cloud-radiation feedback in the tropical oceans and the mai ntenance of the warm pool. Here the diurnal cycle is emphasized. Data from the TOGA COARE Intensive Observation Period is examined and inter preted using an ocean mixed layer model that includes a parameterizati on of the ''skin'' temperature, explicit salinity, a surface heat budg et that includes the sensible heat flux associated with rain, and the contribution of rain to the surface momentum flux. Using a mix of mode ling and observations, three different case studies are examined in de tail: clear and calm, clear and windy, and disturbed. For these typica l sets of conditions and processes in the tropical ocean warm pool, th e upper-ocean structure is clarified so that the skin sea surface temp erature, the bulk surface temperature (at a depth of 1 cm), and the te mperature at 0.5 and 5 m below the surface (which is the level that bu oys and ships routinely observe ''surface'' temperature) can be interp reted. Sensitivity studies are conducted with the model to investigate the roles of wind speed, precipitation, ocean turbidity, and ocean in itial state in modulating the radiation-induced diurnal cycle in SST. It is found that in high insolation, low wind regimes that the skin te mperature may be as much as 30 degrees C warmer than the 0.5-m buoy te mperature. Spatial distribution of the diurnal amplitude of the SST ar e calculated for the global Tropics, and speculations are made regardi ng the implication of the SST variability to the tropical climate.