Correction and assessment of dust sources in WRF/Chem, caused by wind erosion, over West Asia

In this study, using remote sensing and calculating the physical parameters related to dust emission, the soil erodibility as a criterion of dust sources has been re-calculated and added to the WRF/Chem model, to replace the default dust sources (based on topography) in WRF/Chem, over West Asia. SEVIRI Dust RGB products, as the remote sensing data, and ECMWF-ERA5 meteorological data have been extensively used in the geographical identification of dust sources and calculation of their activity. Over 1100 dust sources have been identified by the aim of dust RGB images, and converted to dust frequency map, which at the next step, converted to the weighted frequency map, by applying the turbulence (friction and convection velocity), and 10m wind speed. One of the key innovations in this study is the combination of dust event frequencies (weighted frequencies) with the meteorological factors, including friction velocity, convection velocity, and 10m wind speed. The results show that the weighted dust frequencies are effective in improving the simulation of dust concentration. The spatial distributions of the new dust sources are similar to the default dust sources (based on Ginoux function), and different in many other regions. New redefined dust sources include regions in Iraq, Syria, eastern Iran, northern coasts of Oman Sea, and the Aral Sea. There are considerable regions in the new dust source map, including eastern coasts of Caspian Sea and southern coast of Persian Gulf, which in comparison to the default dust sources are not identified as active dust sources. The distribution and magnitude of the dust concentrations and the results of the WRF/Chem simulations of dust concentrations for two major dust episodes with the new dust sources and comparing them with the simulations with default dust sources show significant improvements. The new erodibility maps as the new West Asia dust sources, developed in this study, result in a relative improvement in the simulated dust concentration. It cannot be expected that all WRF/Chem dust simulations with the new dust sources in any region of the study area produce more accurate results.     One of the most important purposes of this study was to provide a new dust source map that makes the WRF/Chem results of dust concentration more reliable; therefore, it can be used in operational and warning advisory systems for sand and dust storms. It is shown that for some cases the simulated dust concentrations are not different, using the weighted dust frequencies or only the dust frequencies. But in some other cases (especially eastern Iran), there are major differences between the simulated dust concentration and station data, in a way that confirms the significant role of weighted frequencies in reaching better erodibility factors (dust sources) in comparison to the dust frequencies alone. The capability of the WRF model is a key factor in correcting the dust sources. Good accuracy of WRF in wind simulation makes it a capable model in predicting the temporal and spatial variability of the dust storms. However, the stochastic variables, including the turbulence, can affect the accuracy of model.