CR 49:247-254 (2011)  -  DOI: https://doi.org/10.3354/cr01031

ABSTRACT: Climate change is considered one of the main environmental concerns of the 21st century. Increased variation and changes in mean temperature and precipitation are expected to dominate future changes in climate and affect crop productivity. It is highly important to identify regions vulnerable to climate change and to identify suitable adaptation practices that can sustain productivity to some extent. In the present study, an iterative χ² method was applied to detect recent possible climate change in extreme daily minimum and maximum temperatures for 5 different regions (Birjand, Boujnord, Mashhad, Sabzevar and Torbat Heydarieh) in Khorasan Province, Iran, during a recent 15 yr period and a prior 30 yr period. The method determines the values of extreme daily temperature that are most significantly different between the prior and recent periods and gives a measure of the weekly significance of that difference. We determined the percentage change in the frequency of the number of extreme days for each period of continuous significant weeks. In all 5 regions, a few days of extreme low minimum temperature (especially in Mashhad and Sabzevar) were experienced during the recent period. The major changes in climate for minimum temperature were determined in Mashhad. In this region the highest percentage  change of climate (min. temperature) occurred during Week 33, when a 41% decrease of extreme low minimum temperatures occurred. In Mashhad the highest warming (decrease in days of min. temperature) occurred during late March to late December. Among 5 regions during the recent period some weeks experienced a greater number of days of extreme high maximum temperature (except Torbat Heydarieh and Birjand). In Torbat Heydarieh, the highest percentage  change occurred during Week 24, when a 26% decrease of extreme high maximum temperatures was detected. In ­Torbat Heydarieh, the highest cooling occurred from April to early December.

KEY WORDS: Global climate change · Daily minimum and maximum temperature · Temperature variability