Temporal Variations of Aerosol Optical Parameters Resulting from the Aging of a Model Aerosol Number Size Distribution

Abstract

Aerosol number size distributions are subject to aging, i.e., to temporal variations. The aging of a Junge number size distribution due to a multitude of processes was modeled by Junge and Abel. The pertinent changes with time of aerosol optical parameters, such as the volume extinction coefficient, the single-scattering albedo and the asymmetry parameter, are calculated in this paper. It is found that the volume extinction coefficient is relatively constant with time when thermal coagulation is considered, but decreases by a factor of 2 within five days when rainout, washout, and other cloud-related processes are regarded. The single-scattering albedo and the asymmetry parameter are approximately constant with time. With these parameters known, absorption and backscattering to space can be estimated. Their temporal variations are largely determined by the change with time of the volume extinction coefficient.