Atmospheric Ice and Water Content Derived from Parameterization of Nimbus 6 High-Resolution Infrared Sounder Data

Abstract

A radiative transfer model of spectral infrared radiation in cloudy atmospheres is applied to the most complete set of radiance observations currently available from the Numbis 6 HIRS instrument. The radiative characteristics of clouds in the High-Resolution Infrared Sounder (HIRS) channels are investigated using the discrete-ordinate method for approximating the solution of the radiative transfer equation as it is applied to non-isothermal, inhomogeneous cloudy atmospheres. A method for the estimate of cloud compositions from multi-spectral HIRS radiances, including both shortwave and longwave CO2 channels, is developed. Theoretical calculations of the upwelling radiance at satellite altitude for a number of thicknesses involving middle level and cirrus clouds are carried out. The resulting theoretical radiances are then parameterized and an empirical method to determine cloud type and ice and water content of the clouds is described. Satellite passes from five days over the western United States are employed to test the empirical parameterizations of the theoretical results. Comparisons of the cloud-type determinations with NOAA 4 mosaic are shown to agree reasonably well. Cloud ice and water content derived from the parameterizations of the HIRS data is compared with that obtained from the Air Force Three Dimensional Neph-analysis (3DNEPH) program. Examples of the application of this technique to global mapping of ice and water content are displayed.