Identification of the Circulation Patterns Producing Dust over South and Southwest of Iran (Case Study, Fars Province)

In recent years، dust storm in western part of Iran، especially Fars province، caused various problems for people. The aim of this research is the identification of circulation patterns producing dust storms over Fars province. For this purpose، firstly the Code number 6 of current weather at 12 GMT belongs to 8 synoptic stations during the statistical period of 1992-2003 has been extracted. This code shows dust with sources out of meteorology station. Then the relationship between 500 Hpa circulation patterns in Middle East and dust days at chosen stations were studied by circulation-to-environmental method. For the 500 Hpa circulation patterns data، Masoodian circulation patterns calendar was used. The results of the research showed a significant correlation between 500 Hpa circulation patterns in Middle East and dust days over Fars province. So that، Circulation patterns numbers 5، 6، 3-6 and 8 have the most relationship with dust days over Fars province. Totally، the circulation pattern number 5 was the dominant circulation pattern and circulation number 6 was subdominant circulation pattern over Fars province in that period. These two circulation patterns are active in warm seasons. The circulation pattern number 3-5 has the least correlation with dust days over Fars province. The station of Lar has reported the highest amount during the dominant circulation patterns.