Abstract
The studies in recent decades show that many natural disasters such as tropical severe storms, hurricanes development, torrential rain, river flooding, and landslides in some regions of the world and severe droughts and wildfires in other areas are due to El Nino-Southern Oscillation (ENSO). This research aims to contribute to an improved definition of the relation between ENSO and seasonal (autumn and winter) variability of rainfall over Iran. The results show that during autumn, the positive phase of SOI is associated with decrease in the rainfall amount in most part of the country; negative phase of SOI is associated with a significant increase in the rainfall amount. It is also found that, during the winter time when positive phase of SOI is dominant, winter precipitation increases in most areas of the eastern part of the country while at the same time the decreases in the amount of rainfall in other parts is not significant. Moreover, with negative phase of SOI in winter season the amount of rainfall in most areas except south shores of Caspian Sea in the north decreases, so that the decrease of rainfall amount in the eastern part is statistically significant.
Highlights
Islamic Republic of Iran has arid and semiarid climates and for which the occurrence of rainfall is unreliable
The studies in recent decades show that many natural disasters such as tropical severe storms, hurricanes development, torrential rain, river flooding, and landslides in some regions of the world and severe droughts and wildfires in other areas are due to El Nino-Southern Oscillation (ENSO)
The results show that during autumn, the positive phase of SOI is associated with decrease in the rainfall amount in most part of the country; negative phase of SOI is associated with a significant increase in the rainfall amount
Summary
Islamic Republic of Iran has arid and semiarid climates and for which the occurrence of rainfall is unreliable. Droughts and floods, which are common in many parts of the country, can significantly effects the people lives, agriculture, livestock, forestry, water resources, tourism construction, industry and many other local activity It has long been a matter of debate whether and how the El Nino Southern Oscillation (ENSO) warm and cold extremes influence Iranian rainfall. Later work by Nazemosadat and Cordery revealed that the autumn rainfall in Iran negatively is correlated with ENSO [2] Their relationships were found to be strongly and consistent over the southern foothills of the Alborz mountains, northwestern districts and central areas. In another study he (Nazemosadat, 2001) found that for the main parts of Iran, winter average SOI positively related with winter rainfall, but for a few stations cold events generally were coincided with low rainfall (drought). This paper aims to contribute to an improved definition of the relation between ENSO and seasonal (autumn and winter) variability of rainfall over Iran
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