Atmospheric circulation and precipitation in Southwest Asia: The role of the Arabian Anticyclone in precipitation of Iran

Abstract

Arabian Anticyclone (AAC) is one of the components of atmospheric circulation in Southwest Asia and is effective in the precipitation of Iran. The study investigated the role of AAC position in October to May precipitation in Iran. For this purpose, ERA-Interim gridded data were used from 1981 to 2010. The relationship between AAC and precipitation in Iran was conducted in three categories light (1–10 mm/day), moderate (10–30 mm/day), and heavy (more than 30 mm/day) precipitation. The geographical location of the AAC center was extracted by defining the maximum geopotential elevation criterion for all of the above-mentioned groups. The results indicated that AAC had an independent closed center between 42 and 85% of the rainy days while it was branched or merged with Siberian and Tibetan high pressures in other cases. The maximum frequency of AAC centers was observed on rainy days at 41.62% on the east coast of the Arabian Peninsula and northwest of the Arabian Sea at the lower level. This position was mostly in the lower level of the troposphere with light and moderate precipitation. In addition, there was another frequency in the Gulf of Aden at the 700 and 500 hPa levels. During heavy precipitations, the anticyclone at all three levels was more active on the east coast of the Arabian Peninsula and west of the Arabian Sea with east-west movements. In general, the AAC seems to be related to the spatial patterns and intensity of precipitation in Iran with the movement of the north, especially the east.