Frequency Variation Of Cold Wave And Its Influencing Factors In Hexi Corridor From 1966 To 2018

As an extreme meteorological disaster,cold wave is one of the main disastrous weather in winter.It can cause large-scale cooling,heavy snow,glaze,frost and other disastrous weather and will brings serious harm and great loss to agriculture and animal husbandry production,transportation and communication,national economy and ecological environment.Hexi Corridor is located in the hinterland of Eurasia and is located in the arid and semi-arid area of Northwest China,it is one of the commercial grain production bases and important ecological barrier in China,at the same time,it is also one of the main paths for cold air masses to move southward,which is greatly affected by cold wave and sensitive to climate change,the impact of climate change is more complex.At present,the domestic and foreign scholars mainly focus on the cold wave process,cold wave occurrence mechanism and prediction methods in monsoon area,there are few studies on the occurrence frequency and influencing factors of cold wave in Hexi corridor.Therefore,based on the daily minimum temperature and average temperature data of 15 national benchmark stations in Hexi Corridor from 1966 to 2018,this paper analyzes the frequency variation characteristics and spatial distribution of cold wave activities in Hexi Corridor from 1966 to 2018,and analyzes the influencing factors of cold wave activity change by using atmospheric circulation index,annual average temperature data and geographical parameters.The conclusion is as follows:(1)The frequency of cold wave at single station of Hexi Corridor in the last 53 a from 1966 to 2018 showed a downward trend,with a decline rate of-0.085 times /10 a,and it has experienced multiple abrupt changes in the past 53 years,the abrupt change of cold wave is obvious;The regional cold wave showed a downward trend from 1966 to 2018,with a decline rate of-0.021 times / 10 a,which failed to pass a significant test,and the mutation characteristics were not obvious,the frequency of cold wave activity decreased continuously.(2)The cold wave activities in Hexi Corridor are mainly from September to May of the next year,which in October,February and April are the most active three months of cold wave activities.The frequency of cold wave in autumn and spring showed a downward trend,with the decreasing rate of-0.036 times/10 a and-0.088times/10 a,respectively.The frequency of cold wave in winter showed a slight upward trend,which was 0.035 times/10 a.(3)The frequency of cold wave is relatively low in the middle region between Beida River and Heihe River,while in the north of Beida River and east of Heihe River is the high value area of cold wave,mainly concentrated in the north and southeast of Hexi corridor.The high value center is located in Mazongshan area and Minqin area.The frequency of cold wave has obvious regional differentiation.(4)The correlation analysis shows that the cold wave frequency in Hexi Corridor has the best correlation with the APVII and CQ,and have passed the significance test of α = 0.05,which shows that the APVII and CQ have a great impact on the cold wave frequency of the Hexi corridor,and it is positively correlated and negatively correlated with the Asian zonal circulation index and the Sea of Okhotsk high index,respectively.In addition,the Asian polar vortex center and 500 h Pa circulation field also affect the cold wave frequency in Hexi corridor.(5)From the perspective of the correlation coefficient between the annual mean temperature and the frequency of cold wave activity,the correlation between the frequency of cold wave activity and the annual mean temperature is relatively high,the correlation coefficient is 0.304,and the annual mean temperature of the corridor has been increasing in recent 53 years,the warming rate is 0.442℃/10 a,there is an obvious anti-correspondence relationship between them.The frequency of cold waves in Hexi corridor will change with the change of latitude from 1966 to 2018,with the specific performance is that the latitude has increased by one degree every northward,the frequency of cold wave decreased 1.108 times in inter annual,1.012 times in autumn,1.212 times in winter and 0.827 times in spring,in Gaotai County,a low value area was formed,as the latitude continues to rise,the frequency of cold wave increased 1.275 times in inter annual,1.187 times in autumn,1.003 times in winter and 0.931 times in spring.(6)In terms of underlying surface parameters and cold wave sensitivity index weights,land use types have the highest sensitivity to cold wave activities,while the longitude has the lowest sensitivity to cold wave activities;at the same time,the frequency of cold wave is also restricted by topography,which makes the spatial distribution and change trend are different.