Spacebased Observation of Oceanic Origin of Continental Water Balance

Over a decade of Tropical Rain Measuring Mission (TRMM) rainfall and spacebased observation of integrated moisture transport (IMT) and evaporation-transpiration (ET) are used to characterize the ocean source of continental water balance. The IMT across the continental coastline is estimated using satellite measurements of column integrated water vapor, wind-stress at the surface, and cloud drift wind, through a statistical model. Over the Western Africa Monsoon region, our IMT data combine onshore transport at surface with offshore transport aloft, and identify two rain regimes controlled by moisture from two different oceans. Rainfall in the south is caused by moisture from the Gulf of Guinea, which peaks in June. Rainfall in the north (Sahel) is driven by moisture from the Atlantic in the west, which peaks in August. In South America, the change of continent mass resulted from water storage change is monitored by the Gravity Recovery and Climate Experiment (GRACE), which is a geodesy mission to measure Earth's gravity field. The IMT integrated over the continent coastline, less the river discharge, is found to balance the mass change measured by GRACE in magnitude and in phase with the annual cycle. The moisture transport from the ocean is also used to compare with the change of precipitation and evaporation-transpiration over the continent given by a number of data products. Water and mass conservation are used to validated various spacebased products.