Land Surface Water and Energy Estimates in the Global MERRA-2 Reanalysis

Multi-decadal reanalysis datasets have been widely used to study the global terrestrial water and energy cycles. The driving component of the land surface water budget is the incoming precipitation forcing, which has traditionally been generated by the atmospheric general circulation model component of the reanalysis system following the assimilation of atmospheric temperature and humidity observations. However, in MERRA-2 the land surface is driven with a mix of (i) model-generated precipitation at high-latitudes, (ii) a remotely sensed over Africa, and (iii) a daily gauge-based precipitation products elsewhere. This approach represents an evolution of the method used in the land-only MERRA-Land reanalysis. In this presentation, the precipitation climatologies and the resulting land surface conditions are evaluated regionally and for the reanalysis time period (1980-present) against available independent observations. MERRA-2 provides generally improved land surface conditions when compared to MERRA, its predecessor. Improvements include enhanced estimates of soil moisture, terrestrial water storage, runoff, screen-level temperature and turbulent fluxes.