中国冬季大范围极端冷、暖日的时空变化特征

Characteristics of the widespread extreme cold and warm days over China in winter

利用1961—2020年中国逐日地表气温观测资料,综合考虑其概率密度分布与空间范围,定义了全国一致冷日、一致暖日与全国反位相型冷暖日3种全国性极端冷、暖日,并分析了各自的变化特征。结果表明,中国冬季全国性极端冷、暖日共960 d。其中一致冷日358 d,一致暖日271 d,反位相型冷暖日331 d。在21世纪前,一致冷日数与累计强度随时间逐渐下降,冬季与2月的一致冷日数均在20世纪80年代出现显著突变减少;一致暖日则随时间呈上升趋势,其中只有12月的一致暖日数在70年代末突变增加。21世纪前冬季一致冷(暖)日的下降(上升)受2月的影响最大。进入21世纪后,1月一致冷日的增加使冬季一致冷日出现小幅度上升,而2月一致暖日迅速减少导致冬季一致暖日在21世纪初有小幅度下降,之后1月一致暖日的迅速增加使得冬季一致暖日继续上升。冬季、1月、2月的反位相型冷暖日的天数均在20世纪70—80年代突变减少,21世纪10年代前,冬季反位相型冷暖日主要受到2月变化的影响,之后1月的贡献更大。

Using the daily observational dataset of the surface air temperature in China from 1961 to 2020,and considering their probability density distribution and spatial extent,three kinds of temperature extremes were defined:the spatially consistent cold days,spatially consistent warm days,and extreme days with north-south dipole temperature in China during winter.The results show that a total of 960 days of the winter temperature extremes occurred in China.Among them,there are 358 consistent cold days,271 consistent warm days,and 331 extreme days with north-south dipole temperature.Before the 21st century,the days and intensities of the consistent cold days showed decreasing and weakening trends respectively,and the cold days of winter and February decreased abruptly in the 1980s.Meanwhile,increasing and strengthening characteristics can be seen in consistent warm days,but only consistent warm days in December increased abruptly in the late 1970s.The decline(rise)of spatially consistent cold(warm)days during this period was most affected by changes of February.After entering the 21st century,it was the variations of the spatially consistent cold and warm days in January that led to the small increase of cold days and the increase of warm days in winter.Except for December,extreme days with north-south dipole temperature in winter and other months all showed abrupt decline in the 1970s and 1980s.Before the 2010s,the decline of the extreme days with north-south dipole temperature in winter was mainly influenced by the variation in February,after then,the variation in January played a dominant role.