GEOGRAPHICAL RESEARCH ›› 2017, Vol. 36 ›› Issue (6): 1171-1182.doi: 10.11821/dlyj201706014

• Orginal Article • Previous Articles     Next Articles

Spatio-temporal changes in extreme UTCI indices in China

Qinqin KONG1,2,3(), Quansheng GE1, Jingyun ZHENG1()   

  1. 1. Key Laboratory of Land Surface Pattern and Simulation, Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China
    2. University of Chinese Academy of Sciences, Beijing 100049, China
    3. School of Geography, Beijing Normal University, Beijing, 100875, China
  • Received:2017-01-04 Revised:2017-04-04 Online:2017-06-30 Published:2017-06-30

Abstract:

Based on ERA-Interim reanalysis data, this study investigated the spatio-temporal changes in extreme UTCI indices in China during 1979-2014. The results show that national average heat indices have significantly increased. Hot nights (1.50 d/10a) and summer minimum UTCI (0.63 °C/10a) have larger increasing rates than hot days (1.32 d/10a) and summer maximum UTCI (0.24 °C/10a). The number of hot days and hot nights has increased rapidly since the early 1990s. In comparison, most of cold indices show no significant trends, except for winter maximum UTCI (0.42 °C/10a). Cold days and cold nights series show distinct characteristics in different periods, with both high mean values and large fluctuation ranges in the 1980s and the period after the mid-2000s, and both low mean value and small fluctuation range in the period between them. Particularly during recent 10 years, China has been facing both severe extreme heat stress in summer and cold stress in winter. From the perspective of regional differentiation, heat indices increase over most of China. The largest increasing magnitudes of hot days and hot nights were observed over eastern Xinjiang and central Inner Mongolia, namely 3-4.80 d/10a and 4-5.94 d/10a, respectively. Winter maximum UTCI increased at 82.04% of China, with the largest increasing rates (1.20-2.18 °C/10a) in central and western Inner Mongolia and northern Shaanxi. Other cold indices show no significant trends in most of China, and their changes are relatively small. In addition, the comparison between extreme UTCI indices and extreme temperature indices shows that, both of them reveal increasing hot days and hot nights and decreasing cold days and cold nights in most parts of the country. Nonetheless, the increases in hot days and hot nights indicated by extreme temperature indices have relatively large magnitudes, and the phenomenon of hot nights increasing faster than hot days is more prominent. Besides, decreasing trends in cold days and cold nights show larger magnitudes and spatial extent for extreme temperature indices.

Key words: extreme UTCI indices, spatio-temporal changes, China