83rd Annual

Wednesday, 12 February 2003
Comparison of latent and sensible heat fluxes over tropical oceans observed by TRMM and DMSP satellites
Alice Fan, SAIC, Hampton, VA; and B. Lin
Poster PDF (381.8 kB)
The latent and sensible heat fluxes between air-sea interface are important parameters in understanding the atmospheric/ocean heat and fresh water transports. This study estimates these fluxes over tropical oceans (30N to 30S) using Tropical Rainfall Measuring Mission (TRMM) Microwave Image (TMI) data and compares the result to those of GSFC version 2 products of surface turbulent fluxes derived from SSM/I data collected by DMSP satellites.

TMI has dual polarized 10, 19, 37 and 85 GHz and vertically polarized 21 GHz channels. The brightness temperature (Tb) measurements at these frequencies are used to retrieve surface air specific humidity (Qa) based on Tb simulations of a microwave radiative transfer model (Lin et al. 1998). The sea surface skin temperature (SST) and near sea surface wind speed (WS) are estimated empirically from the TMI Tb values. Air temperature is obtained by adding the gradients between the skin and air temperatures of European Centre for Medium-Range Weather Forecasts (ECMWF) to the TMI estimated SST. With these meteorological parameters, the bulk algorithm based on the stability-dependent aerodynamic model for TOGA COARE (Fairall et al. 1997) is used to calculate sea surface latent and sensible heat fluxes.

The TMI estimates are compared to the GSFC version 2 products of surface turbulent fluxes derived from SSM/I measurements onboard of DMSP F-8, F-10, F-11, F-13, and F-14 satellites. Both data sets are averaged into 1X1 degree gird boxes. The zonal means of latent heat fluxes from these two data sets correlatted well between 20N and 20S degree, although the TMI values are lower than those from SSM/I by 3 to 15 w/m^2. The TMI flux values are higher than those from SSM/I by 6 to 17 w/m^2 at higher latitudes, because of higher wind speed estimations at the current estimation. The monthly zonal averaged latent heat differences for entire tropical oceans (30S to 30N) are very small, only about -6.6, -3.2, -2.9, -2.0, -7.2, 1.1, 2.9, and -2.4 w/m^2 for the first 8 months of 1998. The sensible heat from TMI are lower than those from SSM/I across all compared latitudes by 6-7 w/m^2. The spatial and temporal differences and the diurnal variations of latent heat fluxes will be presented.

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