Water balance over oceans observed from satellites

We have derived and validated water transport integrated over the depth of the atmosphere using satellite observations of surface wind-stress, cloud drift winds, and column-integrated water vapor, through a statistical model. The divergence of the transport is the fresh water flux between the ocean and the atmosphere at time scales longer than a few days, and we show that it has fewer uncertainties than estimating evaporation and precipitation separately using satellite data. The annual mean surface water flux is found to agree with climatological water discharge from continent and is about 20% lower than Budyko's text book value published more than 3 decades ago. The annual variation of the flux adjusted for climatological river discharge from continent agrees with ocean mass loss measured by the Gravity Recovery and Climate Experiment (GRACE) both in amplitude and in phase. The continental water balance over South America was examined through the moisture advection across the coastline and the mean surface flux over the continent is 4% higher than Budyko's value. The water influx from the oceans to the continent minus river discharge agrees with the mass change in phase and amplitude of the annual cycle. The results imply 20% and 12% uncertainties in the river discharge for all continents and for South America respectively. Distributions of seasonal, inter-annual, and longer-term linear variations of the surface fresh water flux over global oceans are also examined.