Identification of Circulation Patterns Producing Floods Over Southwest of Iran Case: Mond Basin

The aim of this research is identifying the relationship between circulation patterns and floods over southwest of Iran. For this purpose, the daily runoff data of 12 hydrometric stations of Mond basin was prepared and its basic runoff was separated by manual method. Mond basin is one of the sub-basins of Persian Gulf that with about 47000 km2 areas is located in Southwest of Iran and covers major parts of Fars and Bushehr provinces. The data of selected stations include the statistical periods of 1961-2000. For synoptic analysis of relationship between circulation patterns and floods the circulation-to- environment method has been selected. For this purpose, the circulation patterns of elevation 500 hPa which was prepared by Masoodian's was used. The results showed there is a significant correlation between circulation patterns HGT 500 hPa of Middle East with the mean daily floods over Mond basin. So that at all the selected stations, circulation pattern number 2 (Black sea trough) with 35.70 percent, number 7 (Syria sea trough) with 29.14 percent and number 1(East of Mediterranean Sea trough) with 25.24 percent had the most relationship with floods of the basin.The map of sample day of circulation pattern No. 2 shows a ridge on Europe and a trough on the Black sea. The most important synoptic phenomena on the map of sample day of circulation pattern No. 7, is a trough that is started from Russia and has continued to Syria. Circulation pattern No. 1 is a trough that is located on the Mediterranean Sea.