بررسي آماري پديده گرد و غبار و تحليل الگوي وزش بادهاي گرد و غبارزا در شهرستان سبزوار

Statistical Survey of Dust storms and Analysis of Wind induced Dust Regimes in Sabzevar

The results showed that dust occurrence has an increasing trend in Sabzevar within the study period with a higher likelihood during May and June. Also more than 71 percent of the duststorms occurred during the afternoon. Dominant wind within the annual Wind Rose and Dust Rose is from east. Annually 85.4 percent of overall wind flow and 81.36 percent of dust-flow blow in east-west direction. Hence it seems that a new canal is created at this direction. This finding is in harmony with topographical conditions of the area. Annual "Dust Rose" showed that average speed for Dust Winds is 8.75m/s and about 50 percent of them have speed of over 9m/s. The study of monthly Dust Rose indicated the influence of different atmospheric systems over the formation of Dust events in Sabzevar. From May to September, duration of sun shine increases and extensive plains and playas within the area has led to the predominance of thermal systems with prevailing "Dust Wind" direction from east. From October to May, eastern Dust Wind is decreasing but western and south western Dust Winds increasing due to the predominant of the western systems. For example, prevailing wind direction according to the Wind Rose in February is from east but dominant Dust Wind direction at the same period is completely from west. Comparison of the monthly "Resultant Vector" over the year supports such a behavior. This study can be useful for controlling of the dust sources and to help the regional planning towards a sustainable development.