Abstract:

Using daily temperature data of 46 stations in Anhui province with satellite-based station classification during 1961-2010, annual and seasonal trends of both absolute and relative extreme temperature indices were analyzed. Furthermore, urbanization effects and contributions were also evaluated. The annual maximum of daily maximum temperature (maxTmax) presented insignificant trends, while the annual minimum of daily maximum temperature (minTmax), the annual maximum and minimum of daily minimum temperature (maxTmin and minTmin) showed remarkable increasing trends, especially minTmin. Both warm days and nights presented significantly increasing trends, while cold days and nights showed decreasing trends, however, trends for warm and cold nights were relatively larger. Trends of extreme temperature indices for urban stations were generally more significant than those for rural stations. Urbanization effects had led to a highly significantly increase of maxTmax, maxTmin and minTmin at rates of 0.144, 0.184, and 0.161℃ per decade, with contributions of 100%, 58.8%, and 21.6%, respectively. However, there was no significant urbanization effect for minTmax. Seasonal urbanization effect generally led to increasing trends for absolute extreme indices, which were larger in spring and autumn, while contributions in spring and summer. Urbanization effects induced more significant increasing trends on warm days and nights, and more significant decreasing trends on cold nights, with contributions all above 40%. Contributions for all relative extreme indices were the smallest or insignificant in winter.

Key words: urbanization effect, extreme temperature, trends, Anhui province