5A.4 Development of GSI-based WRF 4DVar system

Zhang, Xin, and Xiang-Yu Huang, National Center for Atmospheric Research

In the past few years, NOAA and NCAR have made lots of efforts to push the operational data assimilation system--- Gridpoint Statistical Interpolation (GSI) system to a community regional data assimilation system. One of the advanced features of GSI is that: coupled with forecast models and their adjoint models, GSI can be turned into a four-dimensional variational (4D-Var) system. NASA GMAO and NCEP have their global models and adjoint models coupled with global GSI to construct the global 4D-Var systems. Recently, NCAR MMM division successfully coupled the WRF model and its adjoint model with regional GSI system. The development of the regional GSI-based WRF 4D-Var system is completed. This regional 4D-Var system is able to assimilate conventional data and satellite data, run with multiple outer loops and with multiple increments configuration. The preliminary test results have demonstrated the advantages of the 4D-Var approach over 3D-Var approach.