Large-scale evaluation of WRF-chem model and dry deposition schemes during a Saharan dust event over the Iberian Peninsula

Atmospheric aerosols significantly influence global and regional climate by interacting with radiation and clouds. These interactions are difficult to represent in atmospheric chemistry models due to their dependence on aerosols' physicochemical properties associated with emission, aging, and removal processes. In the absence of precipitation, large uncertainties arise from the parameterization of aerosol dry deposition (ADD), which could lead to inaccuracies in the estimation of aerosol interactions. In this study, the WRF-Chem model is validated and used to assess (1) its sensitivity to emission sources’ representation and to four ADD schemes coupled with the MOSAIC 8-bin aerosol model (i.e., ADD1 – based on Binkowski and Shankar, 1995; ADD1E – based on Emerson et al., 2020; ADD101 – based on Peters and Eiden, 1992; and ADD301 – based on Zhang et al., 2001); and (2) the impact of ADD on size-resolved dust aerosol load, number, and optical depth during a Saharan dust event that affected the Iberian Peninsula between 7 and August 12, 2010. Results show that all simulation experiments using the different ADD schemes captured the observed horizontal and vertical aerosol layer's structure, concentration, and optical properties, with model skill significantly improving when all emission sources were considered. However, this agreement with observations results from compensating effects of different aerosol size distributions in all ADD schemes. In fact, only ADD1 could reproduce the observed coarse mode shape, with ADD1E and ADD301 largely overestimating the aerosol volume in the 5–10 μm diameter range. Bin-dependent relative differences in dust number, load, and AOD show that of all the schemes, ADD1 offers the best balance between predicted aerosol number in 0.078–1.25 μm range and aerosol load in 5.0–10.0 μm diameter range during the dust event. • A large-scale WRF-Chem model configuration was setup and tested over the Iberian Peninsula during dust event. • Sensitivity to emission sources and aerosol dry deposition (ADD) representations is assessed. • Size-integrated optical properties show higher sensitivity to emissions representation than to ADD. • ADD parameterizations have a large impact on aerosol size distribution and size-resolved optical properties.