جستجوی مقالات مرتبط با کلیدواژه "500 hpa level" در نشریات گروه "جغرافیا"

Storm as one of the natural disasters has affected different regions and caused great economic, social, political and environmental losses. In this paper, after defining storm threshold, data of level 500 HPa height for 40 days of storm during the period (1986-2011) were processed using an advanced factor analysis. And finally, based on the correlation matrix (variance-covariance) and Varmix rotation on the factors, major topography variation centers at 500 hPa that affect heavy storms at Zab River Basin were discovered and analyzed. The results show that, eight centers have been involved in occurrence of storms. Among these eight centers, four centers that have the highest anomalies (R>0.7) at 500 HPa height, are detectable. 1) Axis of Middle East - North Africa to Northern Russia. 2) African tropical areas-Indian Ocean. 3) North Asia-North Europe. 4) The Scandinavian region. Such changes would strengthen and deepen the axis of ridges in these regions at 500 hPa level, and consequently synoptic storm patterns are created. Meanwhile, changes in the first 500 HPa at the first center (Axis of Middle East - North Africa to Northern Russia), have the most influence on the development of storms in Zab River Basin.

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.