Abstract:For studying climatic characteristics and change trend of fog in Hebei Province, based on the observational data from 49 meteorological stations in Hebei Province during 1965-2006, the temporal and spatial features of fog, diurnal variational law and the long term variation trend are analyzed by using the correlation analysis, trend analysis and Mann Kendall test methods. Results show that annual fog days are 15 d in Hebei Province, those in plain are more than 20 d, and in plateau, mountains and hills are less than 10 d. The fog prone season is in autumn and winter, the 15.7% of fog frequency in November is the highest. Except summer, foggy days in plain are more than other topographic regions in general. The turning point of fog in Hebei Province is in the early 1970s. First, it is less from 1965 to 1971 then, after 1972 it experiences a more-less-more variational process. Frequency that fog occurs is the highest at 05:00 BT accounting for 22.2%, and frequency that fog dissipates is the highest at 08:00 BT accounting for 18.8%. The short time fog within 3 hours occurs easily. Foggy days in Hebei Province hava a change trend, stations in piedmont plain show an upward trend mostly, but stations in other topographic regions show a downward trend commonly.