Synoptic analysis and simulation of a widespread dust event in the Urmia Basin

We analyzed a widespread dust event that influenced the Urmia Basin in northwestern Iran from 28 to 31 October 2017. To this end, we applied the Global Forecast System (GFS) data to investigate the origin and the mechanism of the formation of dust storms in this period, and the transport pathways of dust particles toward the Urmia Basin. We also used the Weather Research and Forecasting model coupled with Chemistry (WRF-Chem) and compared the spatial distribution of the simulated dust against the Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) and the Moderate Resolution Imaging Spectroradiometer (MODIS) visible image. A mid-tropospheric trough associated with positive relative vorticity contributed to the development of a surface low pressure and strong winds at lower levels in western Iraq, which caused the emission of dust from multiple sources. The analysis of the simulation results, satellite images, and MERRA-2 indicates that dust storms in western Iraq were mainly responsible for the occurrence of dust events in the Urmia Basin in late October 2017. Dust particles were lifted up to 450 hPa, which made it possible to pass high mountains in western Iran and reach the Urmia Basin. Dust concentration was higher in the eastern compared to the western and southern parts of Lake Urmia. Considering the dominance of westerlies in this region, this suggests that the dried parts of Lake Urmia act as a local source of dust. Our results have important implications for the understanding of the emergence of new sources of dust in the Urmia Basin and the potential impact of dust particles from these sources on climate and environment through a wide range of mechanisms.