Numerical simulation of extreme dust storms in east of Iran by the WRF-Chem model

Iran, located in the desert belt, is characterized by frequently increasing sand and dust storms, especially in the eastern and southern areas and creating adverse environmental effects. Efficient management of these devastating events requires an understanding of their features. One way to understand the dust phenomenon is to simulate and predict. The general purpose of the article is to simulate severe storms in the southeast of the country (120-day-old winds) due to the weather conditions of the region and the display of their source and range inside Iran. Aim of this study: Weather Research and Forecasting-Chemistry coupled model (WRF-Chem.3.6.1) is used to simulate, forecast, and design an alert system for sand and dust storm events (east of Iran). Dust concentration data were collected by Environmental Protection Organization, wind speed and direction data were gathered from the Meteorological Organization, MODIS images, and HYSPLIT model forecast was also used to investigate the path of storms and more accurately forecast and time alerting. Results showed that the main dust emission source in Sistan is the dry bed of the Hamoon wetland. Also during the storms that investigated in this study, transport of dust clouds were observed in the southern part of Iran up to Oman sea because of converging currents (north-south winds in the eastern part of Iran, especially in spring and summer) that create strong winds in lower levels of the atmosphere. The WRF-Chem model had reasonable estimations related to spatial and temporal scales in the study area. Using the global forecasted data as model input data, it was expected to observe bias in concentration estimation versus reality. The model was run for 10 and 30 km spatial resolutions, and results revealed storm formation in Sistan was affected by local geographical properties especially topography features. Based on the results obtained and the experience gained, it can be concluded that most dust storms in the Sistan region began in the late spring and will continue until early autumn season.