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The Persian Gulf and Oman Sea, situated over the northwestern extremity of the tropical Indian Ocean, make up the southern border of Iran (Figure 1). During hot seasons, the sea surface temperatures (SSTs) of these water bodies are high, and a huge thermal trough system is usually dominant over the region (Bitan and Sa’aroni, 1992). The summer SSTs of the Persian Gulf are reported to be the highest in the world (Gabler, 1977).
About 30% of the total rain-bearing air masses coming to the country originate in north Africa, the Red Sea, and western Saudi Arabia (Khalili, 1992). These air masses are known as the Sudan Current; they are categorized as tropical maritime. They produce a significant portion of the total annual rainfall over the southern parts of Iran. Figure 2 shows that the general trajectory of the Sudan Current passes over Saudi Arabia and enters Iran through the Persian Gulf. The occurrence of some heavy winter rainfalls in Shiraz, Fasa, Bushehr, and Bandar Lengeh (Figure 1) is attributed to the movement of the Sudan Current toward Iran (Khalili, 1992).