Tabulation of Mie properties for an effective microwave radiative model

Summary In microwave radiative transfer model simulations of atmospheric convective systems, the Mie calculations usually consume the majority of the computer time necessary for the calculations (70 to 90% for frequencies ranging from 6 to 300 GHz). For a large array of atmospheric profiles, the repeated Mie scattering calculations make the radiative transfer modeling not only expensive, but often impossible. A set of Mie tables, therefore, is developed to replace the actual Mie calculations in the microwave radiation model.The tables are divided into categories of liquid water (cloud water and rain), ice, snow, graupel and hail. The tables are free from restriction on variation of size distribution, particle density and mixing phases. Results from this study show that by using the Mie tables, the total CPU time is reduced by at least one order of magnitude, depending on the frequency. Compared to using full Mie calculation in the radiative model, the bias and root-mean-square (rms) deviation from the Mie tables are less than 1.2 K for any atmosphere with precipitation rates up to 125 mm hr^–1 at any frequency and any viewing angle.The Mie tables are particularly useful in simulating the microwave radiation field over a mesoscale meteorological system. Such a study would not be satisfactory using a Mie parameterization scheme, because one would have to trade off the accuracy and flexibility for modeling efficiency.With 7 FiguresThis research was done under contract at the Goddard Space Flight Center, Greenbelt, Maryland.