Multivariate Analysis of Relationship Between Seasonal Rainfall in Iran with Climate Indices

In this article the relationship between the amount of seasonal rainfall (autumn, winter and spring) and climate indices in Iran have been studied. The Climate indices (the Southern Oscillation(SOI),the North Atlantic Oscillation(NAO), Arctic Oscillation(AO),NINO 3/4,The Multivariate ENSO Index(MEI),Trans_ NINO Index(TNI) and the Pacific Decadal Oscillation(PDO) are used as independent variables. The monthly data of 25 synoptic stations have been used from 1951 to 2003. These stations have the long term data and can cover the most rainfall regions in Iran. The results of this regression analysis show that the relationship between the amount of spring rainfall and climate indices is week. Also the study shows that among of ENSO indices, the NINO 3/4 has more strong relationship with the amount of autumn and winter rainfall. SOI and MEI are in second rank. It seems there isn't significant relationship between PDO and TNI with seasonal rainfall (autumn, winter) has been shown. The relationship between autumn and winter rainfall with MEI and TNI is positive while about SOI is negative. This study also identified that the effects of AO and NAO over the amount of winter rainfall is more than the amount of autumn rainfall. The relationship coefficient between autumn and winter rainfall with NAO and AO is negative therefore there is an inverse relationship between autumn and winter rainfall and AO and NAO indices.

Keywords: ENSO, Southern Oscillation, Arctic Oscillation, The North Atlantic Oscillation, Regression Analysis.