مسيريابي و فركانس بندي سامانه هاي بارشي در غرب ايران (استانهاي كرمانشاه و ايلام)

Tracking and Frequency Count of Rainy Synoptic Systems in the West of Iran (Kermanshah and Ilam Provinces)

The aim of this study is to identify the tracking and origin of the arriving precipitation systems to the region under study and to count the frequencies of these systems. For this purpose, the rainfall data of seven stations of two provinces (Kermanshah and Ilam) were investigated during a 10 years period (1990-99). Therefore, 80 systems were selected. Then, surface level maps and 500Hp of 68 available systems were studied. The analysis was carried out over the central cyclonic of the surface level maps in the 6 hour cycles and upper-level low trough axis level of 500Hp in the 12 hour cycles. The results of indicated that majority of the systems with precipitation for the region were Sudanese systems. Moreover, only the Sudanese systems had more than 300mm precipitation. On the second level of significance were the compo (Mediterranean-Sudanese) systems. The most important compound area of compo systems is the east Mediterranean at the longitude of 33 -36 Eastern and the latitude of 30°-35° Northern. The Mediterranean systems mostly originate from the Adriatic Sea and the central Mediterranean and normally move towards east along the latitude of 35 . So, Monsoon systems bring about precipitation for the target areas at the end of spring and summer during their intensification. Normally, in most of the rainy days, positions of the Mediterranean long wave axis locate at the east of the Mediterranean to the north of the Red Sea (longitude 30°E-40°E). Morever, there is no direct relation between the deepening, of the end of the trough axis and the rate of precipitation.