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Advances in Meteorology
Volume 2016, Article ID 2456809, 8 pages
Research Article

Trends in Extreme Precipitation Indices in Iran: 1951–2007

1School of Geographical Sciences and Urban Planning, Arizona State University, Tempe, AZ 85287, USA
2Faculty of Geographical Sciences and Planning, University of Isfahan, Isfahan, Iran
3Department of Geography and Regional Studies, University of Miami, Coral Gables, FL 33146, USA

Received 1 October 2015; Revised 13 December 2015; Accepted 14 January 2016

Academic Editor: Roberto Fraile

Copyright © 2016 Robert C. Balling Jr. et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


We investigate trends in extreme precipitation in Iran for 1951–2007 using the recently released APHRODITE daily rainfall time series. We find that seven different indices of extreme precipitation all show an upward trend through the study period. The seven different precipitation indices include annual precipitation total, number of days above a certain threshold, maximum precipitation received over a certain period of time, maximum one-day precipitation, and number of days with precipitation above the 90th percentile. A principal components analysis reveals one eigenvector explaining much of the variance in the seven indices and reveals that this component exhibits a strong upward trend for the whole of Iran. On a regional level, we find that the upward trend in extreme precipitation has a strong southwest-to-northeast gradient across the country for all the indices. We repeated all the analyses for 42 stations across the country to compare with the results from the gridded data; trends in extreme rainfall generated from the station data compare favorably with the results from the APHRODITE daily rainfall time series thereby reinforcing the robustness of our conclusions.