The exchange of moisture and heat across the air-sea interface exerts a strong influence on the atmospheric and oceanic circulations. The latent heat flux (or evaporation), contributes significantly to both of these exchanges. Our knowledge of the annual and interannual variability of the moisture flux over large expanses of the global oceans, and particularly the southern oceans, is rather limited because of the lack of available in-situ measurements. Satellite observations represent the only way to achieve the adequate coverage in time and space necessary to fully characterize that variability.
We have developed a method for estimating the latent heat flux over the global oceans based on multi-sensor satellite observations (Jourdan and Gautier, 1994) and computed this flux for a seven year period (1988 to 1994). The surface wind speed and total precipitable water used are Frank Wentz's SSM/I-2 geophysical products, which were mapped onto a regular grid of 0.5 degree resolution and aggregated into monthly averages. Sea surface temperature data is determined by AVHRR data and similarly remapped into half degree monthly averages. This moisture field has been combined with estimates of shortwave, longwave and sensible heat flux, to construct the net surface heat flux and with precipitation to construct the freshwater flux at the ocean's surface. By integrating these fluxes zonally we have calculated the meridional heat and freshwater transport for the three oceans: Pacific, Atlantic and Indian.
Click here to see an animated movie of LHF data.