عنوان مقاله [English]
In order to investigate the pattern of the rainy days of western Iran, the daily rainfall data from 17 synoptic stations in Hamedan, Kurdistan and Kermanshah provinces were used during the period of 1992-2012. The following values of geopotential height at 500 hPa for courses extraction and the factors and weather types during the event precipitation factor analysis and cluster surround procedures were identified in the region. To evaluate the weather data more closely related to sea level pressure, geopotential, vertical velocity, specific humidity, zonal and meridional wind components from the Web site of the National Center for Environmental Studies and forecast / climate science (NCEP / NCAR) obtaining and attempting to atmospheric levels were mapping.The results of the factor analysis on data in 500 hPa geopotential showed eleven factors are involved in daily precipitation total area of these eleven factors of 91% (first factor 60%) of the total variance explained it. The results indicate that the formation of a dominant pattern in middle levels and deep the trough on the Black Sea and the Mediterranean is established That formed the core of the system has led to the north of the Red Sea also drawn its spin can bring heavy precipitation and learning area.The sources of moisture in the region can be found in the Mediterranean Sea and the Persian Gulf, which acts as a hybrid and independent. The results also showed that the most effective factor in rainfall in the region is the Sudanese low pressure penetration to the western regions of the Middle East.