Since April 1994 a new generation of geostationary sounders has been measuring atmospheric radiances in 18 infrared spectral bands and thus providing the capability for investigating oceanographic and meteorological phenomena that far exceed those available from the previous generation of Geostationary Operational Environmental Satellites (GOES). Menzel and Purdom foreshadowed many of the anticipated improvements from the GOES-8/9 sounders. This article presents some of the realizations; it details the in-flight performance of the sounder, presents both validated operational as well as routinely available experimental products, and shows the impact on nowcasting and forecasting activities.

For the first time operational hourly sounding products over North America and adjacent oceans are now possible with the GOES-8/9 sounders. The GOES-8/9 sounders are making significant contributions by depicting moisture changes for numerical weather prediction models over the continental United States, monitoring winds over oceans, and supplementing the National Weather Service's Automated Surface Observing System with upper-level cloud information. Validation of many sounding products has been accomplished by comparison with radiosondes and aircraft measurements. Considerable progress has been made toward assimilation of soundings from clear skies and cloud properties in cloudy regions in operational as well as research forecast models; GOES-8/9 moisture soundings are now being used in the operational Eta regional forecast model.

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*Atmospheric Research and Applications Division, Office of Research and Applications, NOAA/NESDIS, Madison, Wisconsin.

+Cooperative Institute for Meteorological Satellite Studies, University of Wisconsin—Madison, Madison, Wisconsin.