近58年华北地区初、终霜日及无霜期变化特征分析

Variation Characteristics of the Date of First Frost and Last Frost and the Frost-Free Period in North China in Recent 58 Years

基于华北地区90个气象站点1961-2018年地面0 cm日最低温度和平均气温资料,采用线性倾向估计、反距离加权、Mann-Kendall检验、累积距平法,研究了近58年华北地区初、终霜日和无霜期的变化特征。结果表明:(1)在年际和年代际尺度上,华北地区初、终霜日和无霜期均分别呈显著推迟、提前和延长的趋势,从20世纪80年代开始,趋势逐渐明显,反映出气候的变暖趋势。(2)由北向南随纬度和海拔的降低,初、终霜日和无霜期分别呈推迟、提前和延长的趋势,平均气温上升速率越大越显著的站点,其初、终霜日和无霜期推迟、提前和延长的速率也较显著;山区初、终霜日和无霜期分别比平原早、晚和短。(3)初、终霜日和无霜期突变分别发生在1986,1995和1995年,各区域初、终霜日和无霜期均在20世纪80年代和90年代发生突变。(4)初、终霜日和无霜期的等值线呈北移趋势。(5)初、终霜日和无霜期在未来分别呈持续推迟、持续提前和持续延长的趋势,且三者的变化幅度为无霜期>终霜日>初霜日。

Frost will seriously affect normal agricultural activities. It is of great significance to know and grasp the changing characteristics of the first frost and last frost and the frost-free period to guide agricultural production practices,improve the prevention and early warning capabilities of frost disasters. Based on the ground 0 cm daily minimum temperature and average temperature data of 90 stations(1961-2018)in over North China,using the methods of linear regression,inverse distance weighted,Mann-Kendal test and cumulative anomaly to analyze the variation characteristics of the first frost and last frost and the frost-free period in North China. The results show that:(1)In terms of time changes,the first frost date,the last frost date and the frost-free period showing the significant trends in delay,advance and extension,respectively,which gradually became obvious from the 1980 s;The changing characteristics of the frost reflects the climate warming.(2)Along with the decrease of the latitude and the altitude,the first frost date,the last frost date and the frost-free period show trends of delay,advance and extension,respectively. And if the average temperature at the station raised significantly,the rate of delay,advance and extension of the initial,final and frost-free periods is also significant;The first frost date,the last frost date and the frost-free period in the mountain are earlier,later and shorter than those in the plain,respectively.(3)The mutation years of first frost date,last frost date and the frost-free period were1986,1995 and 1995,respectively. And the mutation years of the frost in the three sub-regions all occurred in the 1980 s and 1990 s.(4)Based on different climatic reference periods and different decadal,The locations of the contour lines of the first frost date,the last frost date and the frost-free period all gradually moving northward.(5)The changes in the predicted frost period are roughly the delay of the first frost date,the advance of the last frost date,and the prolonged frost-free period. But there is a slight difference in the magnitude of the change with the descending order of frost-free period,last frost date and first frost date.