Abstract: 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.

Key words: first-frost date, interdecadal variations, Arctic Oscillation, the north of the Yangtze River