Recently upgrades and improvements of WRF 4D-Var system

Since the release of WRF four dimensional variational data assimilation system (thereafter, WRF 4D-Var) to community in 2008, there have been some successful applications of WRF 4D-Var across the community demonstrating the desirable performance of WRF 4D-Var on mesoscale phenomena simulation, such as typhoon, squall line etc..

Recently, several significant software upgrades and improvements are accomplished in WRF 4D-Var system. They are (1) Combined three executables in old WRF 4D-Var system into single executable, which significantly simplify the usage of WRF 4D-Var ; (2) Upgrade the WRF adjoint and tangent linear model to make it compatible with the latest WRF, note that the current WRFPLUS was written based in WRF V2.0.2; (3) Lateral boundary conditions are considered in minimization, which is very important for regional model data assimilation; (4) Data exchanges among minimization package, adjoint model and tangent linear model are moved from disk files to memory copy to reduce the overhead associated with the disk IO. Testing with a benchmark case with these improvements, the computational cost of minimization with identity adjoint and tangent linear model is reduced to 1/5, from 4 hours wall time to 30 minutes; the observations within model lateral boundary nudging area are assimilated more reasonable than before. A prototype of user-friendly , efficient 4D-Var system is available to community users and will be released in next WRF release.