Assimilation of Doppler radar observations to improve the QPF of an IHOP squall line

In this study, we developed a Doppler radar data assimilation scheme within the WRF variational data assimilation system (WRF-Var, including WRF 3D-Var and 4D-Var). Based on the data collected from IHOP experiment, a squall line case is well documented on 12 June 2002 in the North Oklahoma and South Kansas. Totally 12 Doppler radar observations in the region are processed (quality control and coordinate transformation). The WRF 3D-Var assimilation of the Doppler radar data in a cycling mode has been done. Positive impact has been found in the rainfall verification using the NCEP 4-km rainfall observations. We are currently developing the WRF 4D-Var system, and its basic research application will be available soon. Since WRF 4D-Var is built under the WRF 3D-Var frame, the Doppler radar observation operators will be automatically included. Numerical experiments using the WRF 4D-Var system for the IHOP case is also planed. We will show some preliminary results during the conference.