Abstract: As an important ecological security zone in western China,Hexi Corridor of Gansu Province is one of the main areas that govern cold waves in China. Our study was based on daily minimum-temperature data from 15 national base stations in the Hexi Corridor for the period 1966–2018. （The data from Wutonggou and Jinta base stations were for 1966–1988 and 1989–2018,respectively;the other 13 stations yielded data for the entire study period.） Using linear regression analysis,spline spatial interpolation,and the Mann-Kendall trend and mutation test to derive frequency-variation characteristics of cold waves and their influencing factors for the Hexi Corridor,we analyzed data for spring （March–May） from the 53 years 1966–2018. The results show the following：（1） The frequency of single-station springtime cold waves in Hexi Corridor during 1966–2018 had a downward trend （-0.098 times per 10 years）;the cold-wave frequency decreased significantly during 1980–2010 and further slowed after 2010,when it failed the significance test. The frequency of regional cold waves showed a slow downward trend during the entire study period （–0.015 times per 10 years） and failed the significance test. （2） In the three springtime months during the study period,the frequency of cold waves for single stations was 0.46 times per year in March,0.59 times per year in April,and 0.38 times per year in May. Thus,the total number of springtime cold waves for single stations was highest in April and lowest in May;the frequency of cold waves in March decreased significantly （while passing the significance test）,whereas the frequencies in April and May did not decrease significantly （failing the significance test）. （3） The frequency of springtime cold waves is relatively low in the middle region,between Beida and Heihe Rivers,whereas north of Beida River and east of Heihe River,the cold-waves frequency data show obvious spatial differences. The frequency was high in the corridor’s peripheral areas,mostly showing a significant downward trend with a roughly semicircular distribution. Despite an obvious negative correlation between the cold-waves frequency and air-temperature anomalies,the trend of change in the interior area is not obvious. （4） With the significant negative correlation between temperature anomalies and decreasing cold-waves frequency and from the analysis of topographic factors,it is apparent that the springtime cold-waves frequency in Hexi Corridor is mainly affected by climate warming,topography,and atmospheric circulation. We found significant regional differences in cold-waves frequency,and further research could improve the recognition of the process of cold-wave evolution in Hexi Corridor of Gansu Province. This could provide guidance for disaster prevention and mitigation in the corridor and also also help predict the trend of future climate change.

Key words: Hexi Corridor, cold wave, frequency change, influencing factor