Based on the daily temperature records of 76 stations in Hunan province from 1961 to 2014,the four seasons' statuses including their start dates,lasting period etc.,analyzed in line with the industry standards of meteorology.Their variations are also studied through the statistic methods such as wavelet analysis,climatic trend analysis and so on.The results show that the start dates of spring and summer changed clearly with the latitudes,which delayed from south to north in spring and from southeast to northwest in summer;the average numbers of days in each of four seasons in Hunan were 77 (spring),138 (summer),66 (autumn) and 85 (winter),respectively.Over the years,the tendency rate of summer duration change was 2.77 days per 10 years,with the consistency increased.There were two high-value centers in the north and south.The winter tendency rate was-2.93 days per 10 years and the consistency reduced,with the low altitude areas reduced more obviously.From the 1960s to the 2010s,the interdecadal fluctuation of summer duration was most obvious,and after the 1970s,the number of summer days increased continuously.The number of winter days decreased sharply since the 1990s,and the trend continued.%采用四季分明区划分标准对湖南76个气象台站1961 2014年逐日气温统计,得到四季开始时间及长度,运用气候倾向率分析其变化规律,结论如下:湖南四季出现时间有纬向变化特征,入春表现最明显,入夏时间同时受海拔高度影响,影响入冬因素多,表现复杂.四季平均日数分别为77天(春)、138天(夏)、66天(秋)、85天(冬).历年夏日变化倾向率为2.77 d/10a,一致性增多,南北各有两个高值中心.入冬倾向率为-2.93 d/10a,一致性减少,低海拔区域减少更明显.1960 2010年代,夏日年代际波动最大,1970年代后,夏日数连续增多.冬日数自1990年代大幅减少以来,减少趋势仍在持续.
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