The experimental Geosynchronous Imaging Fourier Transform Spectrometer (GIFTS) and operational Hyperspectral Environmental Sounder (HES) represent the next generation of geostationary sounders and are anticipated to lead to a significant advance in the ability to image and sound the atmosphere from geosynchronous orbit. GIFTS and HES are targeted at a horizontal resolution of 4 km, vertical resolution of 1-2 km, and maximum temporal resolution of 10 seconds. As such, they will allow much more rapid and high-resolution retrievals of temperature, moisture, and wind than are available with any current geostationary instrument.

SSEC/CIMSS at the University of Wisconsin-Madison is tasked with testing and developing the forward radiative transfer model and retrieval algorithms for GIFTS and HES. In support of this work, numerical model simulations with high spatial and temporal resolution are used to produce a “truth” atmosphere, which is then passed through the instrument forward model to generate simulated GIFTS top of the atmosphere radiances. Retrievals of temperature, water vapor and winds generated from these radiances are subsequently compared with the original simulated atmosphere to assess retrieval accuracy.

In this paper, we present results from two numerical simulations. The first simulation is of a convective initiation case that occurred on 12 June 2002 during the IHOP field experiment. This simulation realistically depicted the very high-resolution water vapor features and late-day convection over the southern Great Plains. The second simulation is of a jet streak that occurred on 12 March 2003 during the 2003 Pacific THORPEX Observing System Test. Both cases were extensively observed by infrared remote-sensing platforms as well as in-situ observing systems. The wealth of information from instruments very similar to GIFTS/HES (particularly the Scanning High-Resolution Interferometer Sounder (SHIS) and NPOESS Airborne Sounder Testbed-Interferometer (NAST-I)) allows for a qualitative comparison to be made between simulated GIFTS/HES radiances and observed radiances. This comparison will indicate whether simulated radiances contain sufficient fine-scale structure to effectively represent the future instruments. Simulated radiances will be used to provide a pre-launch assessment of the ability of GIFTS/HES to remotely sense fine-scale water-vapor features, to demonstrate the feature-track winds derived from GIFTS/HES radiances, and to develop additional GIFTS derived products.