Using daily temperature data from 599 Chinese weather stations during 1961-2007, the length change trends of four seasons during the past 47 years were analyzed. Results show that throughout the region, four seasons' lengths are: spring becomes shorter (?0.8 d/10yrs), summer becomes longer (3.2 d/10yrs), autumn (?0.5 d/10yrs) and winter (?1.6 d/10yrs) becomes shorter. This trend is different in spatial distribution, namely it is very obvious in northern than southern China, and also remarkable in eastern than western China. Summer change is most obvious, but autumn has little change comparatively. This trend is highly obvious in North, East, Central and South China. In the Southwest starting in the 21st century, summer becomes longer and winter shortens. The trend in the Plateau region since the 1980s is that spring becomes longer and winter shortens. The average annual temperature increased during the past 47 years, and the change of the average annual temperature precedes seasons' length. Thus, the average annual temperature has a certain influence on the length change of seasons.
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