Improving dust simulations in WRF-Chem model v4.1.3 coupled with GOCART aerosol module

Abstract. In this paper, we rectify inconsistencies that emerge in the WRF-Chem code when using the Goddard Chemistry Aerosol Radiation and Transport (GOCART) aerosol module. These inconsistencies have been reported and corrections have been implemented in WRF-Chem v4.1.3. Here, we use a WRF-Chem experimental setup configured over the Middle East (ME) to estimate the effects of these inconsistencies. Firstly, we show that the diagnostic output of PM2.5 surface concentration was underestimated by 7% and PM10 was overestimated by 5 %. Secondly, we demonstrate that the contribution of sub-micron dust particles was underestimated in the calculation of optical properties and thus, Aerosol Optical Depth (AOD) was consequently underestimated by 25–30 %. Thirdly, we show that an inconsistency in the process of gravitational settling led to the overestimation of the dust column loadings by 4–6 %, PM10 surface concentrations by 2–4 %, and the rate of dust gravitational settling by 5–10 %. We present a methodology to calculate diagnostics that can be used to estimate the effects of these applied changes. Our corrections also help to explain the overestimation of PM10 surface concentrations encountered in many WRF-Chem simulations. We also share the developed Merra2BC interpolator, which allows constructing initial and boundary conditions for chemical species and aerosols based on MERRA-2 reanalysis. The results of this work can be useful for those who simulate the dust cycle using the WRF-Chem model coupled with the GOCART aerosol module.