Investigating the mechanism of dust transferring from Iraq to the north of Alborz mountains in Iran

Introduction: Recently, due to climate change, the number and intensity of dust sources are increasing, which leads to the occurrence of dust storms. Atmospheric patterns governing the region, topography and surface features are effective on transportation and dispersion of dust particles. 
Materials and methods: In this study, a severe dust phenomenon on the 3th and 4th March, 2022, was investigated. The dust was emitted from the east of Iraq and passed through the Zagros and Alborz mountain ranges toward the Caspian sea. Meteorological data of the country, satellite data, ERA5 reanalysis data and HYSPLIT and output from the Weather Research and Forecasting Model coupled with Chemistry (WRF-Chem) were used. 
Results: Aerosol Optical Depth (AOD) anomaly compared to the long-term indicated that the intense transport of dust particles from eastern Iraq and reaching the Caspian Sea is not a common phenomenon. Synoptic analysis showed that the dust particles in the source area ascended to the mid-levels of the atmosphere and a large part of the particles passed through the Zagros Mountains. Then, the dust entered the Caspian Sea by passing through the Manjil valley. The vertical profile of WRF-Chem model output showed the ascent of dust particles up to 600 hPa near the dust source and its passage over mountainous areas. 
Conclusion: The main factors in the formation of this unusual dust phenomenon are: severe two-year drought in the Middle East, reduction of vegetation and cold front of the dynamic low-pressure located in the east of the Black Sea, east of Turkey and northern Iraq moving eastward to the Caspian sea in the following hours.