Seasonal atmospheric water budget variability over Gulf of Mexico-Caribbean Sea Basin from satellite observations

The diurnal and monthly varying properties of the atmospheric water budget of the Gulf of Mexico-Caribbean Sea basins are investigated for the Oct '97, Jan '98, Apr '98, Jul '98, Oct '98, and Jan '99 time period. The main scientific objective is to determine how water balance is achieved for an oceanic basin at regional-seasonal scales. To accomplish this, a satellite-only multi-algorithm retrieval methodology is developed. The methodology combines GOES-8 and SSM/I measurements to retrieve precipitable water, cloud water path, precipitation, and various forcing parameters (sea surface temperature, surface wind speed and specific humidity, and air specific humidity and temperature) needed by a model to obtain surface evaporation. The remaining term in the atmospheric water budget equation is the divergence of the vertically integrated water vapor transport. This term is obtained as the residue from the atmospheric water balance equation. The Gulf-Caribbean basin was chosen because it is surrounded by a ring of upper air stations which provides a means for independent estimates of the divergence into the region, both directly and through global model data assimilation. These independent estimates are used to help verify the satellite methodology.; Results indicate that on the fully-averaged monthly time scale, the regional water budget is largely a balance between the divergence and surface evaporation minus precipitation. However, on a diurnally-averaged monthly framework, the regional water balance becomes an interaction between four processes: (1) divergence across the region, (2 & 3) the difference between surface evaporation and precipitation fluxes, and (4) the local rate of change of the vertically integrated water vapor. Comparison of satellite divergence retrievals with independent estimates derived from sounding data and ECMWF's global model analyses exhibit relatively good agreement. The results bode well for use of a satellite-based water budget retrieval methodology for applications in open ocean areas where operational global analysis systems are data deficient.