HESS Hydrology and Earth System Sciences HESS Hydrol. Earth Syst. Sci. 1607-7938 Copernicus Publications Göttingen, Germany 10.5194/hess-12-1309-2008 A precipitation-based regionalization for Western Iran and regional drought variability Raziei T. 1 Bordi I. 2 Pereira L. S. 3 Soil Conservation and Watershed Management Research Institute (SCWMRI), Tehran, Iran Department of Physics, University of Rome "La Sapienza", Rome, Italy Agricultural Engineering Research Center, Institute of Agronomy, Technical University of Lisbon, Lisbon, Portugal 10 12 2008 12 6 1309 1321 Copyright: © 2008 T. Raziei et al. 2008 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://hess.copernicus.org/articles/12/1309/2008/hess-12-1309-2008.html The full text article is available as a PDF file from https://hess.copernicus.org/articles/12/1309/2008/hess-12-1309-2008.pdf

The spatial distribution of the seasonal and annual precipitation was analyzed in western Iran using data from 140 stations covering the period 1965–2000. Applying the Precipitation Concentration Index (PCI), the intra-annual precipitation variability was also studied. Furthermore, nine precipitation-derived parameters were used to regionalize climate in western Iran using principal component analysis and clustering techniques. Results suggest that five spatially homogenous sub-regions can be identified characterized by different precipitation regimes. The spatial pattern of seasonal precipitation seems to be highly controlled by the wide latitudinal extent of the region and by the pronounced orographic relieves, and the time of occurrence of the maximum precipitation varies from spring in the north to winter in the south. <br><br> The time variability of dry and wet periods in the identified sub-regions was analyzed using the Precipitation Index (PI) and the existence of any long-term trend was tested. Results show that the northern and southern regions of western Iran are characterized by different climatic variability. Furthermore, a negative long-term linear trend in the north and a weak positive trend in the south of the study area have been detected though they are not statistically significant.

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