The sea surface temperature field in the eastern tropical Pacific, with its strong asymmetry about the equator, annual and interannual variability, and links to climate are of great interest to PACS. However, our understanding of the processes that control sea surface temperature in this region is lacking and uncertainties in existing climatologies of the surface heat flux, wind stress, and precipitation are large. The ITCZ and the warm water north of the equator both move north and south annually, but the details of the coupling between the two are unknown.
From April 1997 through September 1998, in a study for PACS, sites at 3 S and 10 N
along 125 W are being occupied with moorings equipped to collect accurate time series of surface meteorology and upper ocean temperatures, velocities, and salinities. The two sites span strong gradients in ocean temperature, from the cold tongue south of the equator to the warm water found to the north, and cloud cover and precipitation, from the stratus decks south of the equator to the ITCZ found toward the north. Data from the moorings will improve our understanding of the air-sea fluxes in the eastern tropical Pacific and be used to examine the processes that control sea surface temperature. In collaborative work the accurate fluxes and sea surface temperature data will support examination of climatologies and of the performance of ocean and coupled models in this region. It is anticipated that the improved air-sea fluxes and understanding of local atmosphere-ocean coupling will also motivate further studies into the role of meridional sea surface temperature gradients in driving the atmosphere and into the interaction of the surface temperature field and the location and strength of the ITCZ.
Here, we will show preliminary results from the field work. We will present an overview of the observations and comparisons of observations with gridded products from climatologies and numerical weather prediction. We will discuss placing these observations in context of the 1997-1998 ENSO event and of climatology.