Four-dimensional variational data assimilation of high resolution X-band radar observations over the Dallas-Fort Worth metroplex

The Variational Doppler Radar Assimilation System (VDRAS) is applied to observations collected by X-band radars over the Dallas-Fort Worth metropolitan area. VDRAS is specifically designed to assimilate radar observations of Doppler velocity and reflectivity. In order to cope with attenuation issues affecting short-wavelength radars, the rainwater mixing ratio is here estimated using a technique based on dual-polarization observations. Preliminary results obtained from application to a severe storm case study are presented. The overall consistency of the resulting analyses demonstrates the feasibility of the proposed approach. The incorporation of observations from X-band systems sampling the lower atmosphere with high spatial and time resolution allows producing detailed analyses near the surface. In particular, the wind field reveals the capability to detect regions of low-level convergence associated with organized updrafts.