High-frequency Daily Temperature Variability Over China And Its Contributing Factors

High-frequency daily temperature variability has an inevitable impact on human daily activities and health.Three measures are calculated based on the daily maximum\minimum\mean temperature of the four seasons in China,and one of which is applied to further analyze its temporal and spatial evolution characteristics and contributing factors,for its better description of temperature variation between adjacent 2-day periods.The main conclusions are as follows:(1)The distribution characteristics of high-frequency daily temperature variability in four seasons of China,which are characterized by day-to-day temperature fluctuation DTD,sliding standard deviation DVT and standard deviation SD,are highly consistent.Compared with DVT and SD,DTD is a more direct measure that individuals experience climate change;(2)The annual courses of climatological DTDs of the daily maximum\minimum\mean temperature(expressed as DTD_Tmax,DTD_Tmin and DTD_Tmean,respectively)are characterized by the double peaks of “mid-spring and late autumn”,the lowest value in summer,and the peak value of mid-spring is greater than that of late autumn;(3)DTD_Tmax in spring shows a significant increase trend over China,with the largest in the Yangtze River basin;DTD_Tmin increases significantly in the North China Plain,Hetao area and Inner Mongolia,but decreases significantly in Northwest China;DTD_Tmean increases significantly in the North China Plain and decreases in Tibet,but the trend in other regions is basically not significant;(4)The first modes of EOFs in China's spring DTDs are characterized by nationally consistent interdecadal variations,and weak to strong mutations occur in the early 21 st century;while the second modes mainly reflect the inter-annual regional “seesaw” characteristics;(5)The interdecadal temporal and spatial variation characteristics of the first modes of DTDs are well correlated with the Atlantic multi-decadal oscillation index(AMO)and the North Atlantic Oscillation Index(NAO),while the interannual temporal and spatial variation characteristics of the second modes are related to the Pacific Subtropical High Ridge Position Index(PSHRP).The spring DTDs in China show opposite characteristics in the AMO cold and warm phase,and the DTDs' mutation points are slightly later than the AMO(NAO)phase transition.The most affected areas were the middle and lower reaches of the Yangtze River and the Hetao area and its northwest;(6)East Asian subtropical Jet(EASJ)and East Asian Polar-Front Jet(EAPJ)enhance and approach each other in AMO positive phase,and further contribute to the decadal shift of the high-frequency daily temperature variability in spring over China.In addition,the highfrequency daily variability of EASJ and EAPJ also has a high correlation with the interannual characteristics of the regional ‘seesaw' in China's spring DTDs,especially for DTD_Tmax and DTD_Tmean.