Assimilating radar, surface, and profiler data for the Sydney 2000 forecast demonstration project

A variational scheme for the analysis of low-level wind data is presented, and its performance during a recent field experiment is described. The analysis scheme finds an optimal fit to the data and a background field under the constraints of a dry boundary layer model. The scheme was run at the Sydney 2000 Forecast Demonstration Project and assimilated data from two Doppler radars, a surface mesonet, and a boundary layer profiler. With a few exceptions, the analysis system ran reliably over the 6-month period of the project, providing wind fields every 10 min. Described herein is the performance of the system in tracking a number of different phenomena, including sea breezes, a southerly change, and the low-level convergence associated with a severe tornadic hailstorm. Finally, the analyzed wind fields are verified using independent aircraft data and compared with winds calculated by the more traditional dual-Doppler approach.