Assimilating radar, surface, and profiler data for the Sydney 2000 Forecast Demonstration Project

As part of the Sydney 2000 Forecast Demonstration Project a mesoscale assimilation system was run to provide realtime analyses of the low level wind field. The system assimilated data from two C-band Doppler radars, a mesonet of approximately 25 surface stations and a 54.1 MHz profiler. The analysis system finds a model solution which is the best fit, in a least squares sense, to a prior analysis and all available data over a specified time window. The numerical model solves the dry, anelastic, Buossinesq equations for the flow in the lower troposphere. The best fit is found by minimizing a cost function using the adjoint equations to the forward model.

The system provided analyses of the low level wind every 10 minutes throughout the Forecast Demonstration Project. At the conference we will present statistics on the performance of the algorithm along with a description of a number of case studies. Phenemona that were well captured by the analysis system included sea breezes, Southerly Busters and the November 3rd hailstorm/tornado event. Finally, we will compare and contrast our analysis system with the more traditional dual Doppler technique.