Modern real-world data assimilation systems require significant human and computational resources in order to preprocess, quality control, bias correct, simulate, and efficiently assimilate observations from a wide range of in-situ and remote-sensing platforms. Given this complexity, maintaining flexibility to data assimilation technique is a key challenge in developing an advanced community data assimilation system used for a wide range of deterministic/probabilistic, convective-mesoscale-synoptic-scale NWP applications.

To address this issue, the community WRF model includes an advanced data assimilation system known as WRF-Var. The WRF-Var system is the operational data assimilation system of the US Air Force Weather Agency (AFWA), as well as a number of international WRF partners in Asia, the Middle East, and Europe. This talk will firstly review the motivation and challenges associated with developing a single, multi-technique (3D-Var, 4D-Var, hybrid ETKF/Var) system. The relative merits of each permutation will be given using examples from applications of WRF-Var in AFWA theaters of operation. Key areas of collaboration, including the common use of the JCSDA's community radiative transfer model (CRTM) will be highlighted. Finally, results from recent observation impact studies, including AMSU radiances and COSMIC refractivities, in AFWA applications will be given.