The importance of direct readout satellite data in sub-synoptic scale data assimilation and numerical weather prediction

Observations, directly read out from polar orbiting and geostationary satellites are vital to sub-synoptic scale analysis and forecasting over the Australian Region. Physically based methods are used for determining temperature, moisture and total ozone from NOAA satellite radiance observations from the High Resolution Infrared Sounder (HIRS), Microwave Sounding Unit (MSU) and Solar Backscatter Ultraviolet Radiometer (SBUV/2) instruments. Physical methods have also been used to estimate wind at hourly intervals from visible and infrared observations from the Geostationary Meteorological Satellite (GMS-5). The quality of these observations and their impact on forecasts in the Australian Region are documented. The studies reported here show the importance of TIROS Operational Vertical Sounder (TOVS) data to forecasting and that, in particular cases, their impact is pivotal. The benefits of a two-instrument approach, using the SBUV/2 and HIRS for estimating total ozone amount is also shown. The studies have also quantified the utility of both visible and infrared image-based hourly cloud motion vectors on forecasts, using conventional intermittent (cycling) and continuous (nudging and variational) data assimilation techniques. The vital role which these high temporal and spatial resolution wind data can play in tropical cyclone forecasting is also shown. (C) 1997 COSPAR.