Variability of Precipitation in Southern Part of Iran and Linkage to Indian Ocean Sea Surface Temperature

In this research, the impact of sea surface temperature on precipitation variation in southern part of Iran is examined using monthly data from meteorological and water resource institute during 1974-2005. The majority of precipitation occurs during the rainy season from October to May. Regional spatial precipitation on variability was identified by Empirical Orthogonal Function (EOF), applied to deterended monthly precipitation anomaly data. The first and second components, which determine 54 to 82.7% of the variance of the total precipitation from October to May were selected for the study. To study the rainfall variations, SST anomaly, moisture flux, geo-potential height and sea level pressure were analyzed for wet and dry years of first and second mode of EOF. The pattern of sea surface temperature anomaly for wet and dry years shows that the sea surface temperature of Indian Ocean has an important role on precipitation variation over the south part of Iran. In the first mode of EOF which represent 50% of total variance the positive (negative) sea surface temperature anomaly is in the East (west) part of Indian Ocean during wet (dry) years and it is associated with the equatorial easterly (westerly) moisture flux anomaly. In the second mode of EOF the SST anomaly over the Arabian Sea is positive in the wet years but it is a non-dominant feature for the dry years. The Arabian anticyclone has an important role to transfer moisture in lower level of atmosphere from southern water bodies to the cyclone near Iran and displacement of the Arabian anticyclone to westward (eastward) transports more moisture from southern water bodies to the western, south western (southern and south eastern) parts of Iran.