Estimation of a radiative transfer model in the longwave spectral range: sensitivity study and application to real cases

Abstract

The aerosol radiative effect in the longwave spectral range is often neglected in atmospheric aerosol forcing studies, hence very few researches are conducted in this field at local scale, and even less at regional scale. However, strong absorbing aerosols, like mineral dust, can have a small, but non-negligible heating effect in the longwave spectral range which can slightly counteract the aerosol cooling effect in the shortwave. The objective of this research is to perform a sensitivity study of an aerosol radiative transfer model as a function of dust particle properties. GAME model¹, which can compute vertically resolved shortwave and longwave values of aerosol radiative forcing, is used. Before developing the sensitivity analysis, the aerosol radiative transfer model is validated by comparing its outputs with results published previously. Radiative forcing simulations in the longwave have shown an important sensitivity to the following parameters: aerosol size and refractive index, aerosol vertical distribution, humidity, surface temperature and albedo. A couple of strong mineral dust intrusion observed by means of lidar and sun-photometer are also presented in terms of shortwave and longwave radiative forcing.