An Operational System for Generating Cloud Drift Winds in the Australian Region and Their Impact on Numerical Weather Prediction

Abstract

The Australian Bureau of Meteorology has, since June 1992, produced cloud drift wind data for operational use. These data are used in the analysis cycle of the local operational numerical weather prediction system. This paper describes the methodology used for automatically producing cloud drift winds and also for their application to numerical weather analysis and prediction. Local processing of Geostationary Meteorological Satellite digital infrared data into cloud motion vectors has provided several advantages. It ensures timely availability of the data in the Australian National Meteorological Centre for the operational Regional Assimilation and Prediction (RASP) system. It allows quality control and, in particular, height assignment to be closely tied to the RASP system, which is consistent with the long-term requirement for the processing of these remotely sensed data to be done as part of the assimilation system. Importantly, use of the data has resulted in consistent improvements both in forecasts from the RASP system over the Australian region in real-time trials over several months and in forecasts over the Southern Hemisphere in a two-month trial with the Bureau of Meteorology Research Centre Global Spectral Model.