Polynominal Approximation of the Optical Properties of Water Clouds in the 8–12-μm Spectral Region

We have developed a simple approximation for the absorption, extinction and scattering coefficients, infrared emittance, single-scattering albedo, and asymmetry factor of water clouds within the 8–12-μm spectral region. The aforementioned cloud-scattering characteristics are obtained as continuous functions of the wavelength λ liquid water content W, effective reff, and effective veff of the droplet-size distribution. The accuracy of the proposed approximation is shown to be within 6% for the most types of water clouds when compared to the exact Mie theory calculation and integration over the size distribution. At the same time the required computer time is reduced by factor of 102–103.