The central and southwest Asia is usually suffered by dust events of various intensity due to extended arid/desert regions and, therefore, the statistical evaluation of the dust activity over the region has received an increasing interest. This study analyses the characteristics of the dust events (according to their intensity) over the central and southwest Asia during the dusty months May to September from 2010 to 2016, based on visibility observations at 12 meteorological stations in Turkmenistan, Iran, Afghanistan and Pakistan. The dust events are classified based on visibility thresholds such as suspended dust (vis <10 km), blowing dust (visibility between 1 and 5 km) and dust storm for visibility below 1 km. The inter-annual evolution of the frequency of the dust events is examined on monthly basis for both hourly and daily data series (dust hours and dust days, respectively). Depending on intensity, the dust frequency shows remarkable inter-annual and intra-seasonal variability between the stations attributed to differences in topographic and soil characteristics, vicinity to major dust sources, prevailing meteorology and dust-plumes pathways. In general, June and July are the months with the highest dust activity, while the dust events seem to be more frequent during the morning hours, but with large differences between the stations. The highest frequency of the dust storms is observed in the Sistan Basin and around the deserts of southern Afghanistan, while the dust-plume pathways have a distinct north-to-south pattern from the Caspian Sea to the Arabian Sea.

Keywords