关键词: 雾, 等级划分, 气候特征, 变化趋势

Abstract: Based on the observational data of daily fog and visibility at 300 national meteorological observatory stations of China during the period of 1961-2005, spatially and temporally distributive climate characters of fogs of various categories were analyzed through regional division. The frequencies of fog generation and duration in each decade were also calculated. Results show that the fog area was smaller when the visibility of the fog was small. Fog frequencies in most regions generally displayed a evolutional trend of less (the1960s)-more (the 1970s-1980s)-less (since the 1990s) fog days, however, super-dense fog days abruptly increased in the 1970s over the Yangtze River valley and the eastern coastal region. Fogs mostly occurred during 06:00-08:00 o'lock in inland and south coast areas, and 20:00-21:00 o'lock in eastern China and the east coast region. Fogs generally lasted for less than 3 hours in most regions; and those with a duration of more than 12 hours mainly concentrated in the coastal areas, North China, and the Longdong-Shanxi area, and its maximum frequency occurred in the coastal areas, the Sichuan Basin and Yunnan-Guizhou Plateau in the 1990s.

Key words: fog, classification in fog, climate characteristics, trend analysis