Development of GSI-based WRF 4D-Var system

Taking advantage of the latest development of WRF tangent linear and adjoint model (WRFPLUS), the community regional GSI analysis system has been coupled with WRFPLUS to construct a GSI-based WRF 4D-Var. Firstly, the single observation experiment will be presented to demonstrate the implicit evolvement of the flow-dependent background error covariance of 4D-Var; Next, a 10-day 4D-Var analysis/forecast experiment is conducted and in compared with the 3D-Var experiments. In terms of verification score, the 4D-Var beats 3D-Var. Finally, the 4D-Var system runs with different number of processors and the computational efficiency is investigated.