OCEANIC FRESH-WATER BUDGET AND TRANSPORT AS DERIVED FROM SATELLITE RADIOMETRIC DATA

Blended satellite-ship evaporation and SSM/I retrieved precipitation f ields are used to compute oceanic freshwater budget (FWB) and transpor t (FWT) over a 3-year period (1988-90). In order to validate the resul ts, comparisons on monthly, seasonal, and multiyear average bases are performed with ECMWF analyzed field and climatology respectively. For May 1988, differences between ECMWF output and the present monthly est imate are within 2 mm day(-1) (73 cm yr(-1)). Comparison with climatol ogy shows that global discrepancies for longterm average drop down to 36 cm yr(-1) rms with a tendency for satellite-derived results to enha nce climatological. features. Differences are found to correlate with FWB patterns: large positive differences are observed in strong evapor ative regions (eastern tropical Pacific), whereas negative differences are observed over the eastern part of the intertropical convergence z one and the northwestern part of the subtropical basins. Over the latt er, precipitation is strongly dominant in our results, whereas climato logy features rather slightly negative or positive contribution to the FWB (i.e., evaporation). Over the Gulf Stream, for example, climatolo gy indicates that ocean is losing about 100 cm yr(-1) freshwater while FWB is balanced in our computation. FWT is then computed and compared with climatological and in situ estimates. Differences with climatolo gy are found to be 0.2 Sv rms (Sv = 10(6) m(3) s(-1)) in the Atlantic, Indian, and Northern Pacific Oceans, and results generally match esti mates derived from oceanographic data within the same error level, exc ept in the Indian Ocean. The major disagreement is observed in the sou thern Pacific Ocean where results, although confirming the direction o f the FWT, suggest that 2.48 Sv is entering the Pacific Ocean, whereas climatologies only give a northward transport equal to 0.26 Sv.