Arabian Sea’s Moisture Transfer Mechanisms in Pervasive Dry and Wet Periods of Iran

To recognize the Arabian Sea’s moisture transfer mechanisms during the occurrence of pervasive drought and wet years in Iran, a standardized precipitation index (SPI) was applied to quantize Iran’s droughts within the format of a monthly scale. Next, based on a spatial threshold, the drought or the wet years that had engaged about 75% or more of the studied stations (63 synoptic stations) within the period of a cold period (October-April) during 30 years (1986-2016) were defined as the pervasive drought or wet years. In the end, using atmospheric gridded variables, the various mechanisms of the Arabian Sea’s moisture transfer were examined during the occurrence of Iran’s pervasive drought and wet years. The results indicated that during winter, the Asian thermal high pressure reaches its strongest state, its western part is expanded, and, together with the Atlantic Ocean’s dynamic high pressure, they capture the whole of central Asia, the Middle East, and northern Africa. Under these conditions, the high pressure established over the Saudi Arabian Peninsula takes a more western position and this new position disrupts moisture transfer from the Arabian Sea into Iran the result of which would be pervasive dry winters for Iran.