Results of a Joint NOAA/NASA Sounder Simulation Study

Abstract

NOAA and NASA have conducted a joint simulation study to compare the retrieval accuracy of atmospheric temperature profiles and surface skin temperature retrieved from HIRS2, the current operational infrared temperature sounder, and AMTS, a proposed high spectral resolution infrared sounder. Simulations were conducted in as realistic a manner as practical for both clear and partial cloud conditions. Simulated radiances for both instruments were prepared at the University of Denver. The data were analyzed at NASA using a physical inversion technique and at NOAA using a statistical technique. The retrievals were done under information constraints typical of operational retrievals. Results show significant improvement of AMTS compared to HIRS2 for both clear and cloudy conditions. The improvements are relatively independent of the method used but the physical retrievals outperform the statistical retrievals. The combination AMTS-Physical produced retrievals with temperatures in the lower troposphere having an accuracy of about 1°C and seal/and surface temperatures having an accuracy of about 0.4°C, even under partial cloudiness. Actual results may be somewhat poorer but an instrument designed along the fines of AMTS should still represent a significant improvement over accuracies attainable from instrumentation that is current or scheduled in the near future.