The impact of meteorological parameters on PM 10 and visibility during the Middle Eastern dust storms.

Air pollution is one of the most pressing issues in populated Middle Eastern cities, in particular for the city of Ahvaz, Iran, imposing deleterious effects on the environment, public health, economy, culture, and other sectors. In this study, we investigate the relationship between meteorological parameters, PM 10 , AOD, air mass source origin, and visibility during severe desert dust storms (Average 3h PM 10  > 3200 µg m -3 ) between 2009 and 2012. Six of seven such events occurred between February and March. Interestingly, for the seven cases there was always an alarming PM 10 mass concentration peak (137-553 µg m -3 ) between 12:00-18:00 (local time) that was 18-24 h before the dominant peak of the storm (3279-4899 µg m -3 ). The maximum wind speed over the multi-day periods examined for the dust storms is usually observed 6 h before the alarming PM 10 peak. The minimum relative humidity, dew point temperature and air pressure occurred ± 3 h around the time of the alarming PM 10 peak. Wind speed was the meteorological parameter that was consistently higher around the time of the first peak as compared to the second peak, with the reverse being true for sea level pressure. Based on four years of daily data in Ahvaz, PM 10 was positively correlated with wind speed and air temperature and inversely correlated with sea level pressure and RH. An empirically-derived equation with R 2  = 0.95 is reported to estimate the maximum PM 10 concentration for severe desert dust events in the study region based on meteorological parameters. Finally, AOD is shown to correlate strongly (R 2  = 0.86) with PM 10 during periods with severe desert dust storms in the region.