Hosshmand Ataie - Assistant professor of Payamnoor University
Mahnaz shiran - M.Sc. geomorphology, Payamnoor University center of Isfahan, Iran

This study was done in order to identify 500hpa flow patterns and their relationship with the high precipitation years in Iran (1974, 1976, 1982, 1986 and 1992) , Daily data of 500 hPa geopotential height for the region 0º E to 70 º E and 10 º N to 60 º N ,at 2.5 degree resolution, were analysis. A PCA analysis of geopotential heights in S-mode showed that there are seven significant map patterns. This analysis showed that with 13 principal can be explained about 93% of variance. The first map pattern represents deep trough over Iraq, Iran country being located in its east part. The Secondary Map pattern represents a deep trough over the Mediterranean Sea. The third map pattern represents a shallow trough over the Iran. The fourth map pattern indicates a deep trough over Cyprus and a shallow trough, which dominates over Iran. The Fifth Map pattern represents a shallow trough over the Black sea which probably has affected the north and east-north of Iran.The sixth Map pattern is representative of a shallow trough over the Caspian Sea which extends to the black sea and Mediterranean Sea and a high dominates over Iran. The seventh map pattern represents a high over Iraq that surrounds all Iran. Along the northeast of the Caspian Sea a trough is seen that may affect north part of Iran. It was observed that during the domination of the mentioned patterns Iran has higher precipitation years than the average annual precipitation.

Map pattern, High precipitation years, Iran, Principal Component Analysis (PCA), geopotential height