Improving Representation of Mineral Dust Aerosol for Radiative Transfer Modeling in Transport Models

Through interactions with electromagnetic radiation across the broad spectral range, mineral dust aerosols affect the shortwave and thermal IR components of the energy balance, actinic fluxes, and photosynthetically active radiation. This necessitates consistency in representing the spectral (from the UV to the thermal IR) optical properties of dust in transport regional and global models, especially in coupled Earth system models. The fact that optical characteristics depend strongly on the size distribution, composition and shape of aerosol particles greatly complicates the problem of computing optics and radiative fluxes in dust-laden conditions. This paper will report on the development of a dust module DuMo which among other processes includes advanced treatments of dust optics. The dust module DuMo was incorporated into the regional NCAR Weather Research and Forecasting (WRF) model enabling the inclusion of dust radiative impacts in the coupled fashion. In addition to dust optics, DuMo includes physically-based parameterizations of dust emission, and dry and wet removal processes. The coupled WRF-DuMo modeling system was used to investigate the relative importance of major dust characteristics (sizes, composition, shapes) and environmental conditions in affecting radiative fluxes considering several treatments of dust optics calculations of varying complexity. Based on these results we develop recommendations for improved parameterizations of dust optics in transport models and for some satellite sensors. Implications for dust radiative coupling in atmospheric transport models will be addressed.