The study location of the 500 hp level jet sterams and floods in Urmia lake basin

The study of jet streams as one of the mean components of atmospheric circulation system that effects flood is important and necessary. The aim of this research is to identify atmospheric circulation patterns of rainy days and to study location of the 500 hp level jet streams over Uremia lake basin. After determining the flood spatial-temporal index for 189 days of rain tendency flood during 1370-1389, the 500 HPa level high data were processed with factor analysis method and Ward`s method clustering. Finally, seven synoptic patterns of atmospheric middle level were recognized. Research results show that the trough axis has been deepened while occurrence of spread floods and jet streams settled over Mediterranean Sea to northwest of Iran mostly in direction southwest-northeast between latitude 25 to 35 circles.