The Variational Doppler Radar Analysis System (VDRAS) is an advanced data assimilation system specifically designed for ingesting Doppler weather radar observations. The system has been installed at many sites around the world and is typically running using long-range operational S-band or C-band radar networks. The core 4-dimensional data assimilation scheme is based on a cloud-scale model and typically considers a 12-15 minutes time window for the radar assimilation, with 1-3 km spatial resolution.
In this study we explore the feasibility of running VDRAS with rapid update (5 minutes), exploiting the frequent low-level sampling of the atmosphere available within the DFW network of X-band radars. The X-band observations complement the data available from the volume scanning KFWS NEXRAD radar, allowing more accurate three dimensional wind retrievals. In order to cope with strong path attenuation affecting X-band power measurements, a new blended algorithm for the estimation of the rain water mixing ratio is used, replacing the traditional reflectivity-based method.