Study and Simulation of Severe Dust Storms in the West and Southwest of Iran

Resumo

In recent decades, the number of dust events has increased significantly in the west and southwest of Iran. In this research, a survey on the dust events during the period 1990–2013 is carried out using historical dust data collected from seven synoptic stations scattered across the west and southwest of Iran. Using statistical analysis of the observational data, two of the most severe dust storm events that occurred in the region on July 4–7, 2009 and June 17–20, 2012 were selected and analyzed synoptically. NCEP/NCAR reanalysis dataset was used to obtain the required fields including sea level pressure, surface wind field, geopotential height at 500 hPa, and wind and vertical motion at the 850 hPa level. Moreover, weather research and forecasting model coupled with chemistry (WRF-Chem) with two aerosol schemes, GOCART and MADE/SORGAM, were used to simulate the amount of particulate matter (PM10) and its transportation over the studied region. The initial and lateral boundary conditions of the model simulations are provided by Global Forecast System (GFS) data with the horizontal resolution of 0.5°. The calculations demonstrated that the MADE/SORGAM scheme predicted the values and trends of PM₁₀ better than GOCART. Dust plums are formed over Iraq and Syria and then transported to the west and southwest of Iran. Comparing the MODIS satellite images for July 4, 2009 and June 18, 2012 with the corresponding model output showed the good performance of WRF-Chem in simulating the spatial distribution of dust.