Radiative effects of desert dust on weather and regional climate
1University of Athens, School of Physics, Division of Environmental Physics-Meteorology, Bldg PHYS-V, 15784, Athens, Greece
2King's College London, Environmental Research Group, Franklin-Wilkins Building, 150 Stamford Street, London SE1 9NH, UK
3Centro Euro-Mediterraneo per i Cambiamenti Climatici, Viale Aldo Moro, 44 I, 40127 Bologna, Italy
4Atmospheric and Environmental Research (AER), 131 Hartwell Avenue, Lexington, MA 02421-3126, USA
Abstract. Mineral dust aerosols exert a significant effect on both solar and terrestrial radiation. By absorbing and scattering the solar radiation aerosols reduce the amount of energy reaching the surface. In addition, aerosols enhance the greenhouse effect by absorbing and emitting outgoing longwave radiation. Desert dust forcing exhibits large regional and temporal variability due to its short lifetime and diverse optical properties, further complicating the quantification of the Direct Radiative Effect (DRE). The complexity of the links and feedbacks of dust on radiative transfer indicate the need of an integrated approach in order to examine these impacts.
In order to examine these feedbacks, the SKIRON limited area model has been upgraded to include the RRTMG (Rapid Radiative Transfer Model – GCM) radiative transfer model that takes into consideration the aerosol radiative effects. It was run for a 6 yr period. Two sets of simulations were performed, one without the effects of dust and the other including the radiative feedback. The results were first evaluated using aerosol optical depth data to examine the capabilities of the system in describing the desert dust cycle. Then the aerosol feedback on radiative transfer has been quantified and the links between dust and radiation have been studied.
The study has revealed a strong interaction between dust particles and solar and terrestrial radiation, with several implications on the energy budget of the atmosphere. A profound effect is the increased absorption (in the shortwave and longwave) in the lower troposphere and the induced modification of the atmospheric temperature profile. These feedbacks depend strongly on the spatial distribution of dust and have more profound effects where the number of particles is greater, such as near their source.