1954-2005年长江以北地区初霜期变化趋势

采用长江以北地区65个测站1954-2005年秋冬季逐日地面最低温度资料，计算分析长江以北地区初霜出现日期的年代际时空变化特征。结果表明：中国北方地区初霜是由北向南逐渐出现的，初霜发生日期具有明显的年代际变化特征，在20世纪90年代之后，大部分地区初霜日期偏晚的年份逐渐增多。中国北方地区初霜发生日期的早晚与北极涛动的强弱密切相关：当北极涛动处于正位相时，北半球以纬向型环流为主，中国北方大部分地区的初霜期偏晚；反之，当北极涛动处于负位相时，北半球以经向型环流为主，中国北方大部分地区的初霜期偏早。

Characteristics of Interdecadal Variations in First-Frost Date in Northern China During 1954-2005

The daily minimum temperature data at 65 stations from 1954 to 2005 and the definition of first-frost date (first day in autumn and winter when the ground surface minimum temperature is equal or less than 0℃) were used to study the characteristics of interdecadal variations in the first-frost date over northern China. Results show that the first-frost in northern China occurred successively from north to south and the date of the first-frost had remarkably interdecadal variation characteristics, which were not totally identical in the different regions. After the 1990s, the late first-frost years have increased in most regions. Further analysis show that there was a close relationship between first-frost date and Arctic Oscillation Index (AOI). If the AOI was in a positive phase, then the zonally atmospheric circulation dominated in the Northern Hemisphere, and the first-frost was frequently later than normal, and vice versa.