关键词: 持续性雾霾, 阶段性特征, 关键因子

Abstract:

Based on the meteorological observation data and PM_2.5 concentration data，a long－lasting fog and haze weather process occurred from 20 to 24 January 2013 in Shanxi Province was analyzed．The results show that: (1)The persistent fog and haze weather process had obvious characteristics in phases．The changes of relative humidity caused three times converting from mist to fog from 14:00 January 20 to 11: 00 January 23，and PM_2.5concentration increase caused a converting from mist to haze from 14: 00 to 20: 00 January 23．(2)The weak pressure filed and smaller wind speed over the ground，the rising PM_2.5 concentration and increasing relative humidity were beneficial to formation and development of the persistent fog and haze weather． (3)The fog and haze weather was certainly companied with the temperature inversion at boundary layer，but not vice versa． And that would not appear when the relative humidity was below 50% and the daily mean PM_2.5 concentration was less than 75 μg •m^-3 under the temperature inversion weather conditions．The relative humidity in the inversion layer was an index to distinguish the fog and haze．(4)The relative humidity and PM_2.5concentration were two key factors that affect the visibility in phases．When the relative humidity was below 90%，the influence of the relative humidity on the visibility was weaker than PM_2.5concentration，and it would appear haze weather at the moment．But the influence of relative humidity on the visibility was gradually enhancing with relative humidity increase，and it was dominant when the visibility fell　below 1 km．

Key words: persistent fog and haze weather, phase characteristic, key factor