The infrared scatter characteristics of dust aerosol and cloud droplet particle

Abstract

It may be difficult to distinguish the dust and clouds especially for low clouds over ocean from satellite, due to that the dust aerosols can pass through the ocean. The dust clouds are comprised of dust aerosol particles, while the clouds are comprised of water droplets or ice particles. In this paper, using the Mie scatter theory and HITRAN 2008 aerosol complex refractiive index datum, the extinction coefficient, single scattering albedo and asymmetry factor of dust aerosols, water droplets and ice particles which satisfy the log-normal distribution, are calculated at different infrared wavelength and with different particle radius. The results show that the infrared properties of dust aerosols and cloud droplet particles are significantly different. At 10~12μm, the infrared radiance absorbed by ice particles and water droplets are greater than those by the dust aerosols. The extinction coefficient and the asymmetry factor will increase with the particle radius. When the effective particle radius is lower than 2μm, the single scattering albedo will increase with the particle radius. Those different infrared properties provide some information for detecting the dust aerosols and clouds and retrieving the dust or cloud effective particle radius and single scattering albedo from thermal infrared radiance. It is also very important and very meaning to choose some bands for satellite observation by analyzing the infrared scatter properties of dust aerosols, water droplets and ice particles.