干旱区生态环境知识资源中心

Central Asia, a typical arid and semi-arid area, is very sensitive to climate change and is projected to undergo vigorous warming trend in future. However, it is still unclear how extreme temperatures have changed. Therefore, using the daily maximum and minimum temperatures collected from 108 stations in the study area from 1981 to 2015, the spatial-temporal variations in extreme temperature in Central Asia were analysed on both annual and seasonal scales based on 11 indices from The Expert Team on Climate Change Detection and Indices. Results show that: (1) from 1981 to 2015, all extreme temperature values exhibited increasing trends on an annual scale, but maximum temperature (TMAX) increased faster than the minimum temperature (TMIN), leading to an overall increase in the diurnal temperature range (DTR). Most of the stations in Central Asia, except for those in Xinjiang (China), exhibited an increasing trend in DTR, while most of the stations in Xinjiang (China) exhibited reversely significant decreasing trends. (2) TMAX, TMIN and DTR increased significantly, mainly during spring and summer. The trends of most warm extreme indices (warm days, warm nights and warmest days) indicate that the warming mainly occurred in spring, while most cold extreme indices (cool days, cool nights and coldest nights) exhibited significant warming trends in autumn. Dominant warming during spring and autumn can lead to longer summers, which may further accelerate the frequencies and magnitudes of temperature extremes. (3) Additionally, TMAX, TMIN and the percentile-based warm indices all exhibited significant increasing trends from southwestern Central Asia (Turkmenistan) to eastern Central Asia (Xinjiang (China)) via the Tianshan Mountains. Although the percentile-based cold indices showed decreasing trends in this region, they were too minor to offset the overall warming trend. With longer summers, stronger and more prolonged melting seasons were detected in the mountains of Central Asia.