Analysis of trends in temperature data in arid and semi-arid regions of Iran

Trend analysis of climatic variables has received a great deal of attention from researchers recently. The main aim of this study was to investigate trends in maximum (T-max) and minimum (T-min) air temperatures in the annual, seasonal and monthly time-scales for 19 synoptic stations in the arid and semi-arid regions of Iran during 1966-2005. From the results it is clear that the majority of the trends in the annual, seasonal and monthly T-max and T-min time series showed increasing tendency during the last decades, while the increasing trends in the T-min series were stronger than those in the T-max series. The trend in annual T-max and T-min averaged over all 19 stations was 0.090 and 0.444 degrees C per decade, respectively. The T-max and T-min warming trends were more obvious in summer and winter than in autumn and spring. On the monthly basis, the highest T-max and T-min in increases of 0.827 and 1.585 degrees C per decade were found at the stations located in the northeastern corner of the region in January and September, respectively. (C) 2011 Elsevier B.V. All rights reserved.