Testing for long-term trends in climatic variables in Iran

Analysis of long-term climatic datasets is currently of unprecedented interest to the scientific community. In this study, the trends of the annual maximum (T-max), minimum (T-min) and mean (T-mean) air temperatures and precipitation (P) time series were examined in the west, south and southwest of Iran for the period 1966-2005. The magnitude of the climatic trends was derived from the slopes of the regression lines, and the statistical significance was determined by means of the Mann-Kendall, Mann-Whitney and Mann-Kendall rank statistic tests. Pre-whitening was used to eliminate the influence of serial correlation on the Mann Kendall test. The results showed a warming trend in annual T-mean, T-max and T-min at the majority of the stations which mostly began in the 1970s. On average, the magnitudes of the significant positive trends in annual T-mean, T-max and T-min were (+)0.412, (+)0.452 and (+)0.493 degrees C per decade, respectively. However, the variations of the P series were not uniform over the region and there were various patterns (increasing and decreasing trends). (C) 2011 Elsevier B.V. All rights reserved.