HR: 0800h
AN: OS21C-1246    [Abstracts]
TI: Latent Heat Flux at the Sea Surface Estimated from the TRMM Satellite
AU: * Fan, T A
EM: t.f.fan@larc.nasa.gov
AF: SAIC, One Enterprise Parkway, Hampton, VA 23666
AU: Lin, B
EM: bing.lin@nasa.gov
AF: NASA, Langley Research Center, Hampton, VA 23681
AB: Latent heat flux between air-sea interface is one of the dominate factor in atmosphere heat budget, especially over the tropical oceans. Three years (1998-2000) of latent heat fluxes have been calculated using sea surface environmental measurements from the Tropical Rainfall Measuring Mission (TRMM) satellite and the bulk algorithm of Fairall (1996). These results are compared to the global Goddard Satellite-based Surface Turbulent Fluxes version 2 (GSSTF-2) data set and to ship measurements with good agreemenst. GSSTF-2 are derived from Special Sensor Microwave Imager (SSM/I) data collected by a series of satellites from the Defense Meteorological Satellite Program. The input environmental parameters to bulk algorithms include sea surface temperature (Ts), wind speed (WS), and air and sea surface specific humilities (Qa, Qs). These values are estimated for each TRMM pixel. Diurnal variations are available in our dataset due to the processing orbits of the TRMM satellite, which takes 46 days to cover the entire diurnal cycle at each location from 35S to 35N. GSSTF-2 are derived using the gridded daily means of Ts, WS, Qs and Qa. It covers 60S to 60N, but has fewer measurements in the Tropics. Therefore, the seasonal gridded and zonal averages between 35S and 35N are used for comparison between these two data sets. For global oceans over 1998-2000, the correlation coefficients between these two data sets are approximately 0.99 and 0.79 for Qa and WS, respectively. The bias errors are about 0.9g/kg and 0.21m/s. The Qa of TMITF are consistently higher than those of GSSTF-2. The WS are almost the same between 20S and 20N, but TMITF is higher than that of GSSTF-2 for the regions higher than 20 degree of the winter hemisphere. WS is the major cause of the difference between these two data sets. GSSTF-2 uses the daily means of WS from Wentz (1997), and Ts and Ta from the NCEP/NCAR reanalysis. TMITF uses the instantaneous WS and Ts from TMI. Ta is calculated by adding the 6-hourly Ts-Ta difference from ECMWF to Ts. The latent heat fluxes from TMITF are generally a little lower than those from GSSTF-2 except for the regions higher than 20-degree, where TMITF is higher than GSSTF-2. The correlation coefficients and bias errors are 0.72 and -2.98 W/m**2, respectively. Compared TMITF with in-situ ship measurements, the bias (rms) for WS, Ta, Qa, and latent heat fluxes are 0.31 (1.69)m/s, 0.04 (1.35)K, 0.50 (1.49) g/kg and -9.74 (37.08) W/m**2 based on 10 minutes and 20 km collocation. The comparison between GSSTF-2 and in-situ ship measurements have bias(rms) of 0.36 (1.43) m/s, -0.47 (0.94) K, 0.67/(1.40)g/kg, and 0.8 (35.7) W/m**2 based on daily means (Chou 2003).
DE: 3339 Ocean/atmosphere interactions (0312, 4504)
DE: 3360 Remote sensing
DE: 4504 Air/sea interactions (0312)
DE: 1635 Oceans (4203)
DE: 0312 Air/sea constituent fluxes (3339, 4504)
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting