Abstract: Based on daily frozen soil observation data,daily average air and surface temperature,daily average ground temperature at the depth of 5 cm,10 cm,15 cm,20 cm and 40 cm from the seven meteorological stations in Shenyang area,the temporal and spatial variation characteristics of maximum frozen soil depth (MFSD) are analyzed and discussed.The results show that the frozen soil in Shenyang area generally appears in October and melts in April next year.The frozen soil depth is the largest in February-March and the smallest in October;and the MFSD decreases significantly at a rate of -4.8 cm/10 a.In addition,the interdecadal variation of the MFSD also shows a decreasing trend.Meanwhile,the daily MFSD has a significant negative correlation with the daily average temperature and the daily average ground temperature at the depth of 20-40 cm and their correlation coefficients are 0.60 and 0.72,respectively.Mann-Kendall test shows that the MFSD in the seven weather stations shows climatic abrupt change in 1980s.Moreover,the starting and ending dates of maximum frozen soil depth in recent 60 years are delayed and advanced with trend rates of 1 d/10 a and 3.2 d/10 a respectively,and the average duration of frozen soil is 164 d in Shenyang area and shows a shortening trend with a rate of 4.4 d/10 a.

Key words: Maximum frozen soil depth, Correlation analysis, Mann-Kendall test, Climate warming