Abstract:

 Based on the frost observation data of 50 meteorological stations over Jilin Province from 1961 to 2015, the spatial and temporal distributions of the beginningfirst and ending last frost date, frost-free period and their relationships with climate change and geographical factors were analyzed using the methods of linear trend estimation, Mann-Kendall test and Morlet wavelet analysis. The results show that the beginning first and last frost date is postponed, the ending frost date occurs earlier. as well as  The frost-free period becomes are significantly longer. postponed, ahead of time and prolonged with the The climatic trend rates for the beginning and ending frost date and frost-free period are of 1.4 , -2.2 and 3.6 days per decade, respectively.  and the corresponding The number amounts of stations with delayed beginning frost date accounts for occupy 58% of the total stations, that of ahead of ending frost daya is 60% and that with longer frost-free period is 72%  percent of the total stations., respectively, in Jilin Province from 1961 to 2015. The earliest beginning frost date occurs in 1960s. The latest ending frost date is in 1970s. (latest) first (last) frost date occurs in the 1960s (1970s) and tThe shortest frost-free period  and longest frost-free periods appears in the 1970s and the the longest frost-free period happens stage during 2011-2015., respectively. In terms of the spatial distribution, the first (last) frost date and the frost-free period are gradually ahead of time (postponed) and shortened from the west to the east of Jilin. The time series of the ending last frost date and the frost-free period show occur the climatice abrupt changes in 2009 and 2000, respectively. The main cycles of the beginningfirst and the ending last frost date and the frost-free period are all about 3 years. In addition, the beginning first and ending last frost date and the frost-free period are ahead of time, postponed (ahead of time) and shortened (prolonged) with the increasing longitude and altitude (latitude), respectively. The first (last) frost date and the frost-free period is mainly affected by the climatic factors in September (May), respectively.

Key words:  BeginningFirst frost date, Ending Last frost date, Frost-free period, Climatic tendency, Abrupt change, Morlet wavelet analysis, Correlation analysis,  BeginningFirst frost date, Ending Last frost date, Frost-free period, Climatic tendency, Abrupt change, Morlet wavelet analysis, Correlation analysis