All-Sky Microwave Radiance Data Assimilation in NASA GEOS-5 System: Developments, Impacts, and Future Plans

Data assimilation, which combines the information from observations and a short-range forecast, is a powerful tool to estimate the initial state of the atmosphere for NWP forecasts. Assimilating satellite observations from microwave radiometers such as GPM Microwave Imager and Microwave Humidity Sounders in cloudy and precipitating regions can provide critical constraints on meteorological parameters in dynamically sensitive regions and make significant impacts on forecast accuracy for precipitation. To expand the existing capabilities assimilating satellite radiance data in clear-sky condition, the NASA Global Modeling and Assimilation Office (GMAO) has been pursuing efforts to utilize all-sky (clear+cloudy+precipitating) microwave radiance data in the GEOS-5 Atmospheric Data Assimilation System (ADAS). Assimilating surface affected microwave radiance measurements over land is more challenging than over the ocean because of large variability in surface parameters determining surface emissivity for the radiative transfer processes. Therefore, efforts were initially focused on the development of a framework to assimilate all-sky microwave radiance data over the ocean. The project has made considerable progress and the framework to assimilate all-sky microwave radiance data over the ocean is currently being tested for implementation in the GMAO's operational forecast system. In this paper, development and implementation results of data assimilation methodologies to utilize all-sky microwave radiance data in the GEOS-5 system are presented. In addition, efforts to extend this framework to assimilate microwave radiance data over land, which will complement GEOS-5 land surface analyses by improving precipitation analyses and forecasts, are discussed.