Characteristics of Large-scale Synoptic Types Associated with Precipitation over Southern Iran

Atmospheric circulation strongly modulates precipitation patterns throughout the south of Iran. A Characteristics of synoptic types was chosen to investigate their relation to the spatiotemporal distribution of precipitation within the south of Iran. In this study we examined the interannual variability of precipitation in the southern region of Iran and to establish links between the large-scale circulation pattern. In this region, the majority of precipitation occurs during the rainy season from October to May. The present study applied the empirical orthogonal function (EOF) analysis on the monthly precipitation anomaly data obtained from 302 meteorological stations for the 1981–2010 periods. In mostly month, the first mode explains more than 50 % of the total variance of precipitation. Spatiotemporal fluctuation in precipitation over the studied area can be attributed to moisture transport by dynamic factors. This study shows that the position and strength of high pressure over Arabian Peninsula play an important role during the wet and dry years. The results show that during wet years moisture flux in low and middle levels from west of the Indian ocean, Gulf of Aden and Red sea transferred by the high pressure circulation to the central, North of Arabian peninsula and Southern Iran. This high pressure circulation coupled with the East Mediterranean trough over west of Arabian Peninsula at the level of 700hPa. The some parts of moisture flux transferred from Gulf of Aden and the Red sea in the middle and higher levels. In dry years, the anticyclonic circulation is strengthened in the west of the Arabian Peninsula, and blocks moisture advection into the region from the Indian Ocean.