A network of four X-band radars was deployed in central Oklahoma as the first integrated project (IP1) of the Collaborative Adaptive Sensing of the Atmosphere (CASA) Engineering Research Center (ERC) during 2006. The network consists of four dual-polarization X-band Doppler radars separated by about 25 km and is situated in southwest Oklahoma. Two Oklahoma WSR-88D radars, KTLX and KFRD provide coverage at the upper levels of CASA radar network, and are located respectively to the northeast and southwest of and about an equal distance from the CASA network. In the spring of 2007, the data from four CASA radars and two WSR-88D radars were collected along with other high resolution data, including mesonet observations and satellite imagery, near-real-time for about two months in the CASA IP1 Spring Experiment-2007 (CSET-2007).

In this study, a three-dimensional variational data assimilation system (3DVAR) developed at Center for Analysis and Prediction of Storms (CAPS) is used to assimilate observations from this radar network into a storm scale nonhydrostatic NWP model—the Advanced Regional Prediction System (ARPS) with several selected cases from CSET-2007. Data assimilation experiments and Forecasts with CASA and WSR-88D radar data will be compared to those using only WSR-88D radar data and only CASA radar data. Our goal is to estimate the benefit of these small CASA radars to short term convective weather warnings and predictions, in addition to WSR-88D radars.