THE AIR-SEA FRESHWATER EXCHANGE DERIVED FROM NCEP/NCAR REANALYSIS DATA

For the period from 1984 to 1994, the aspects of annual and monthly distributions of air-sea freshwater exchange over global ocean deriv,d from the NCEP/NCAR monthly and daily reanalysis data are studied. The results show that the subtropical oc,ans act as important moisture sources, while Intertropical Convergence Zone (ITCZ)，South Pacific Convergence Zone (SPCZ) and southeast part of South Pacific serve as vapor sinks in global water cycle. Equatorial easterlies plays an unportant role in providing water vapor for Indian monsoon circulation. Some typical realistic features of global air-sea freshwater flux are reproduced in current study, such as the midlatitude rainbelt, the strong subt ropical dry belt, the ITCZ and SPCZ rain belts. Furthermore, some new features have seen shown, a case in point is the pro minent region of net water loss in the North Pacific near the Kuroshio. Both ITCZ and SPCZ are found to bete regions with strong variance. It should be pointed out that in extratropical and subpolar regions of North Atlantic, where precipitation dominates in former studies, a belt of net water loss trending from northeast to southwest is found for the first time and the inside reason may lie in that the transient component of freshwater flux was ignored in former studies, since only monthly data were provided and used in former evaluation. The analysis on seasonal and annual variations of global air-sea freshwater exchange show that the Atlantic Ocean is more drier than the Pacific Ocean as a whole.