Validation of SST and Windspeed from TRMM using North Indian Ocean Moored Buoy Observations

Sea Surface Temperature (SST) and wind speed are important surface parameters that determine air-sea interaction in the tropics. Availability of good quality SST and wind speed data with good spatial and temporal resolution is central to study of tropical climate. There has been a paucity of in situ data on SST and wind over large regions of the Indian Ocean on time scales of days to weeks. Until a few years back only monthly means of SST and wind were available, such as the Levitus data set and the Coupled Ocean Atmosphere Data Set [Levitus and Boyer, 1994; da Silva et al., 1994]. Later, the National Centers for Environmental Prediction (NCEP) Optimally Interpolated (OI) Sea Surface Temperature product [Reynolds and Smith, 1994] consisting of weekly and monthly global sea surface temperature fields became available. This product blends ship and buoy SST and satellite derived SST from the NOAA Advanced Very High Resolution Radiometer (AVHRR). One of the greatest limitations in the AVHRR derived SST is the obstruction by clouds. Other sources of error are atmospheric aerosols and water vapour as well as water surface characteristics. In addition, there is lack of in situ data over several regions. As a result, the weekly analyses are heavily interpolated and smoothed, especially in the summer monsoon region. Recently, the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis Project [Kalnay et al., 1996] has been providing six-hourly fields of zonal and meridional surface wind at a nominal height of 10 metres above the ocean surface. The NCEP reanalysis uses a global data assimilation system , along with observations from land surface, ship, rawinsonde, pibal, aircraft, satellite and other data to produce global fields of various meteorological parameters [Kalnay et al., 1996]. The reanalysis also uses delayed observations, thereby increasing the reliability of the wind and other products. Over the north Indian Ocean the NCEP reanalysis wind captures variability on all time scales longer than a few days [Sengupta et al., 1999]. Very recently, a new satellite product has become available that provides simultaneous measurements of SST and wind with high spatial resolution