Simultaneous Inverse Determination of All Optical Properties of Atmospheric Particles: Improved Results by Using a Realistic Phase Function Approximation

Abstract

Through mathematical inversion of photometric data all optical properties of atmospheric particles necessary for radiative transfer calculations are derived simultaneously. These optical properties are the volume phase function, the volume extinction, and the volume absorption coefficient. Additionally, the apparent complex refractive index and the apparent volume fraction of soot within the particles are calculated from the absorption-to-extinction ratio. The phase function of the particles is approximated by a combination of two Henyey?Greenstein functions, one of them governing the forward and the other the backward scattering. This approximation contains only three constants, one for weighting of the two Henyey?Greenstein functions, and two asymmetry parameters. It describes very well the phase functions known from measurements on airborne particles in the entire range of scattering angles from 0° to 180°. Thus the new results can be used not only for climate modeling but also for remote sensing applications. First results from the new method are compiled and discussed.