Investigation of Spatial Patterns of Seasonal and Annual Precipitation in Western Iran

In this study spatial pattern of seasonal and annual precipitation in west mountainous region of Iran were investigated using a 35 hydrological year from 1965/66-1999/00 in 170 meteorological stations. In order to evaluate and analyze spatial differences across study area, time distribution of precipitation during the year were also investigated using precipitation Concentration Index (PCI). The results showed that the precipitation regime in north of study area with maximum in spring season is different from precipitation regime in southern part of study area where the maximum occur in winter. In general, winter and autumn are the rainy season in middle and southern parts of the study area. Summer is dry season in almost the entire region. In this season rarely precipitation may occur somewhere due to orographic activities. The observed similarity between winter, autumn and annual precipitation maps indicated that the precipitation in the study area is controlled by latitude and altitude factors. This similarity also implies that the precipitation mechanisms and triggers in most fraction of study area are similar.