The spatial and temporal pattern of precipitation in Iran and its relation with ENSO
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Type: Conference paper
Language: English
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ICWR01_134
Index date: 6 December 2009
The spatial and temporal pattern of precipitation in Iran and its relation with ENSO abstract
The spatial and temporal variability of the monthly precipitation in Iran is examined using 29 years data from 44 synoptic stations. The data are subjected to the Principal Component Analysis (PCA) to categorize the temporal rainfall characteristics into homogeneous spatial regions and to clarify the role of the dominant circulation regimes affecting the country. The map patterns and the time series of each Principal Component (PC) scores are obtained. It is found that only nine significant components, accounting for about 63 percent of total variance of the original precipitation data set. These PCs are selected and further subjected to the varimax rotation analysis which divided Iran into 9 climatologically homogeneous zones. The spatial boundaries of these zones are determined using topographic features, the dominant wind-flow patterns and other climate factors. To verify the accuracy of the delineated zones, the PCA was applied independently to the data sets of the stations in each homogenous zone and to the seasonal rainfall distributions of the representative station of each delineated zone. The time series of PC scores revealed the temporal variations of the rainfall in each zone. The relation between the precipitation and the ENSO phenomenon was also investigated and the seasonal correlation between the PC scores and the Southern Oscillation Index (SOI) was computed. Using OND average series, the maximum correlation coefficients between the fourth PC and the SOI was found equal to -0.528 (significant at 99% level). The results of the Pearson correlation indicate the negative significant correlation in all zones (except for zone I) between the SOI and precipitation. This shows the increase in the amount of precipitation during ElNiño (the warm phase) and decrease in precipitation during La Niña (the cold phase). The delineated rainfall zones in this research would be useful on the planning and management of water resources projects in the country.
The spatial and temporal pattern of precipitation in Iran and its relation with ENSO Keywords:
The spatial and temporal pattern of precipitation in Iran and its relation with ENSO authors
Soraya Karimi
Department of Earth Sciences, Shiraz University, Shiraz ۷۱۴۵۴, Iran
Nozar Samani
Department of Earth Sciences, Shiraz University, Shiraz ۷۱۴۵۴, Iran
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