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چکیده
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Today, North Atlantic Oscillation (NAO) index is one of the factors determining the climate in Iran. To investigate its influences on the rainfall of Iran, the two databases are used. First database: APHRODITE1 daily precipitation in the Middle East with 0.25 × 0.25 degrees from the period of 01/01/1951 up to 31/12/2007 with 20,819 days and 2491 pixels in Iran. The second database is the values of the North Atlantic Oscillation (NAO) index for the same period of APHRODITE precipitation data. Then, the correlation between monthly precipitation and North Atlantic Oscillation (NAO) index was calculated using Pearson correlation coefficient and those data with significance level over 95% were selected and finally was determined based on the area of each zone on a monthly and annual basis. The results in an analysis of North Atlantic Oscillation and monthly precipitation in Iran during the Last Half Century show that significant correlation is different between these two variables in time and space scale. However, the correlation is not so straight and significant due to the vast land with different geographic features of Iran and the role of other large-scale climatic systems. The highest positive correlation between these two parameters is in the autumn and winter at the southern coast of the Caspian Sea, the Northwest of the country, and sporadically in the Provinces of Kerman, Fars, Isfahan, Khorasan, and hot and drylands of the central part of Iran. Because in these seasons, there is domination with greater intensity between Iceland low pressure and the Azores high pressure. The highest negative correlation is evident in spring and summer in parts of the South East, the southern coast of the Persian Gulf, Oman Sea, and sporadically in central parts of Iran.
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