Part of #The spatial and temporal pattern of precipitation in Iran and its relation with ENSO# :
Publishing year : 2009
Conference : First International Conference on Water Resources Management
Number of pages : 7
Abstract: The spatial and temporal variability of 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 temporal rainfall patterns into homogeneous spatial regions and to clarify the dominating circulation regime of the country. The map patterns and the time series of each Principal Component (PC) scores are obtained. It has been found that only nine significant components account for about 63 percent of the 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, dominant wind-flow patterns and other climate factors. To verify the accuracy of the delineated zones, the PCA was independently applied to the data sets of the stations in each homogeneous zone and to the seasonal rainfall distribution of the representative station of each delineated zone. The time series of PC scores revealed the temporal variations of rainfall in each zone. The relationship between the precipitation and the ENSO phenomenon was also investigated and the seasonal correlation between PC scores and Southern Oscillation Index (SOI) was computed. Using the OND average series, the maximum correlation coefficients between the fourth PC and the SOI were found to be equal to -0.528 (significant at 99% level). The results of the Pearson correlations indicate a negative significant correlation in all zones (except for zone I) between SOI and precipitation. This shows the increase in the amount of precipitation during the ElNio (the warm phase) and precipitation reduction during La Nia (the cold phase). The delineated rainfall zones in this research would be useful in planning and managing water resources projects in the country.