عنوان مقاله [English]
Dust storms are one of the common phenomena in arid and semi-arid areas of the world. With regard to the heavy impacts of these storms on socio-economic issues, human health and environment preservation have turned into universal concerns. Dust storms mainly stem from powerful turbulent winds and air fronts or desert surface erosion. Through a storm, huge amounts of dust rise from the soft and fine surface of deserts, and visibility falls below 1000 meters. Due to the prevalence and the high frequency of dust storms in Khuzestan province and other eastern areas of Iran, the present study aims at the synoptic analysis of the pressure and humidity patterns in those places during dusty days with a visibility of less than a kilometer in an 11-year statistical period from 2000 to 2010 as well as an experimental seasonal (hot and cold) period. The corresponding data were provided from the meteorological office of Khuzestan. They included information about horizontal visibility, relative humidity, precipitation, and wind speed and direction. Also, satellite images were used to determine the source and the direction of dust on the day when the phenomenon culminated. To identify the sustainable and non-sustainable atmospheric patterns, unsustainability indices were analyzed according to skew T graphs. Analysis of the maps indicated high-altitude patterns of the mid layers of the atmosphere, a Mediterranean ridge stretching to the east, an increase in the western high-pressure gradient along with a reduction in humidity, and an increase in the high-speed nuclei. This played a role to intensify the reduction of horizontal visibility in the first period. In the second period, dust pressure patterns, eastern African ridge, and anti-cyclonic circulatio led to a stable atmosphere. In the third step of the study, the pressure declined at certain times during the day, and some stations recorded precipitation. It was attributed to a relative in the southwest of Iran. Satellite images showed the direction of the dust moving from the southern Iraq and northern and central Arabia.