为了深入认识气候变暖背景下陕西省极端气温事件变化规律,根据陕西省1955—2017年20个气象站逐日最高和最低气温资料,利用软件RClimDex(1.0)计算10种极端气温指数,辅以线性拟合、M-K突变和累积距平、相关分析等方法,分析了陕西省极端气温时空变化特征。结果 表明:(1)近63 a陕西省极端最高气温、极端最低气温及表征暖指数的夏日、热夜、暖昼和暖夜日数均呈增加趋势,表征冷指数的霜冻、冰冻、冷昼和冷夜日数呈显著减少趋势,多数极端气温指数突变年份集中在20世纪90年代中后期—21世纪初。(2)空间上,极值指数和表征极端气温暖指数在多数站点呈增加趋势,表征极端气温冷指数在多数站点呈减少趋势; 镇安、定边和铜川站的各指数倾向率变幅最为明显。(3)近63 a来陕西省白昼增温幅度低于夜间增温幅度,暖夜日数上升趋势快于暖昼,冷昼日数下降趋势快于冷夜,存在气温昼夜指数变化的不对称性。陕西省极端气温事件主要受日最高、最低温升高的影响,而日最高温的上升对各指数影响更为明显。
In order to have a deep recognition of the variation features of extreme temperature events in Shaanxi Province under the influence of global warming, based on the daily maximum and minimum temperature data of 20 meteorological stations in the period of 1955—2017 in Shaanxi Province, 10 types of extreme temperature indices were calculated by RClimDex(1.0). Thus, spatial and temporal characteristics of extreme temperature events were analyzed by linear fitting, Mann-Kendall(M-K)mutation test, cumulative departure and correlation analysis, etc. The results showed that the occurrence of summer days(SU25), tropical nights(TR20), warm days(TX90), warm nights(TN90)had the obvious increasing trends; the monthly maximum value of daily maximum temperature(TXx)and monthly minimum value of daily minimum temperature(TNn)showed the increasing trends of 0.17℃/decade, 0.19℃/decade; on the contrary, the occurrence of frost days(FD0), ice days(ID0), cool days(TX10)and cool nights(TN10)were found to decrease significantly; most of the sudden changes of extreme temperature indices concentrated from the middle and late 1990s to the beginning of the 21st century; in terms of spatial distribution, most stations of extreme indices as high temperature events and extremal indices showed the increasing trend, while extreme indices as low temperature events showed the inverse trend; the most obvious variations of index tendency rates were found in Zhenan, Dingbian and Tongchuan stations; in recent 63 years, the daily temperature increase was lower than that at night; the increasing trend of TX90 was faster than that of TN90, and the decreasing trend of TX10 was faster than that of TN10. The above results indicate that there is an asymmetry of temperature and diurnal index changes in Shaanxi Province. The extreme temperature events in Shaanxi Province are mainly affected by the rise of the highest and lowest temperature in the day, and the rise of the highest temperature in the day has more obvious influence on each index.
