Heavy fog occurred in most areas of middle and south of Hebei Province and Tianjin for 3 days successively from 30 November to 2 December 2010,during which Shijiazhuang experienced a 34 h dense fog,including a 7 h strong dense fog.The diagnostic analysis on structure characteristics of successive heavy fog boundary layer and the formation,development and maintenance,and dissipation of the fog was made based on intensive automatic weather station data and Tianjin 250 m meteorological tower gradient observation data as well as conventional observation data and NCEP/NCAR reanalysis data.The result shows that prior to the foggy weather,the continuous east wind on surface is beneficial to the accumula-tion of water vapor.When the east wind turns to north wind,the vapor begins to condense,and eventual-ly,becomes heavy fog.After the formation of heavy fog,the direction of wind turns to east again,helping maintain and strengthen the fog density.The long-time SW warm and wet flow under 850 hPa and the in-version on the near surface layer are the main causes for the durative heavy fog.The water transfer of the low-level three branches of vapor and reconstruction of southwest jet at 850 hPa are responsible for the for- n mation of the heavy fog directly.During the strengthening period,the wind speed on boundary layer is 1-2 m·s-1 ,especially during the strong dense fog,the wind speed is only 1 m·s-1 .When the wind with speed greater than 4 m·s-1 travels down to the ground surface,the heavy fog disperses affected by the de-stroyed inversion.%提2010年11月30日至12月2日，冀中南部及天津地区出现了一次大范围的大雾天气，持续时间长达3 d，其中石家庄浓雾持续时间长达34 h，强浓雾持续时间7 h。利用加密自动站、天津市250 m气象铁塔梯度观测资料，结合常规气象资料和NCEP／NCAR再分析资料，对连续性大雾边界层结构特征以及大雾的形成、发展维持和消散进行了诊断分析。研究得到：大雾形成前期地面持续东风，有利水汽的聚积；当地面风向转为偏北风时促进水汽凝结，致使大雾形成，大雾形成后再次转为长时间偏东风有利大雾的维持和加强；850 hPa以下西南暖湿气流和近地面层逆温的长时间维持，是平流大雾持续的主要原因；低层3支水汽的输送及850 hPa的西南急流重建直接导致了强浓雾形成。大雾维持加强期间，边界层风速为1～2 m·s-1，尤其是强浓雾期间，风速仅为1 m·s-1；当边界层4 m·s-1以上西北风速从250 m逐渐下传至地面时，逆温层破坏，大雾天气结束。
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