Abstract:

 Based on the daily average temperature data from the 46 representative meteorological stations in Jilin province during 1961-2016, the start dates and durations of four seasons and their main properties and change trends were calculated according to climatic division method of seasons and analyzed, respectively. The results show that the regionally averaged values for beginning dates of each season are April 27, July 8, August 16 and October 8, respectively.   The durations for each season are 72.0 d for spring, 39.0 d for summer, 53.0 d for autmn, and 201.0 d for winter. In addition, the spatial distribution characteristics of the above-mentioned factors are obvious. The averaged beginning dates of the first half year are earlier in the west than in the east; however, those in the second half year are earlier in the east than in the west. The average duration of summer is longer in the west than in the east and vice versa for those of spring and winter, while that of autumn has little variation throughout Jilin province. Besides, there is no summer in the east of Jilin province. In the recent 56 years, the regionally averaged beginning dates of spring and summer are ahead of time for 0.7 d and 1.3 d per decade, respectively, and those of autumn and winter are postponed for 1.3 d and 1.1 d per decade. More specifically, the beginning dates of spring in the east and of winter in most parts of Jilin province change significantly. Moreover, the regionally averaged durations for spring and winter decrease with the rates of 1.0 d and 1.8 d per decade, inversely, that for summer increases with a rate of 2.8 d per decade. The duration of autumn in the west of Jilin province is shortened with a ratio of 1.3 d per decade, while that of east Jilin is prolonged with a ratio of 1.0 d per decade. It is obvious that the summer is prolonged in the western and central parts of Jilin province and east Yanbian state, and the winter in the most parts of Jilin province is shortened especially in east Jilin.

Key words: Season, Beginning date, duration of season, climate tendency rat