河北平原冬季连续两次特强浓雾天气特征及成因分析  

Analysis on the characteristics and causes of two consecutive heavy fogs in Hebei Plain in winter

作　　者：索春男 闫春旺 张敏 SUO Chun-nan(Cangzhou Meteorological Bureau,Cangzhou,Hebei 061001)

机构地区：[1]河北省沧州市气象局,河北沧州061001 [2]内蒙古大学生态与环境学院,内蒙古呼和浩特010021

出　　处：《农业灾害研究》2020年第4期75-78,共4页Journal of Agricultural Catastrophology

基　　金：内蒙古大学高层次人才科研启动基金项目(21800—5195121)。

摘　　要：利用2019年2月18—23日河北省国家站地面、高空观测资料以及NCEP再分析资料,从环流形势、温湿场、动力场及边界层特征等方面对2019年2月20日和2月21日清晨河北平原局地出现能见度不足50 m的特强浓雾天气进行特征和成因分析。结果表明:本次过程雾强度大,能见度低,持续时间短,午后能见度回升明显,主要以辐射雾为主;两次大雾发生在大尺度下沉运动背景下,高空环流形势稳定,中层风速小,地面处于高压前部,有利于冷空气南下造成河北平原大雾天气;大雾发生时温度场1000 hPa以上具有弱逆温或等温特性,1000 hPa与地面气温之差为3℃~6℃,表明200 m以下近地面存在强逆温,大气层结构稳定,边界层高度低,有利于大雾的形成和维持;湿度场具有“下湿上干”特点,“上干”高空无云,有利于晴空辐射降温,“下湿”有利于近地面空气达到饱和;雪后充足的水汽和辐射冷却造成了20日强浓雾的形成;而由于近地面强降温使空气达到饱和形成了21日清晨的强浓雾过程。Based on observation data and NCEP reanalysis data from February 18 to February 23,2019.Considering the circulation situation,temperature and humidity field,dynamic field and boundary layer characteristics,the characteristics and causes of two heavy fogs witch visibility less than 50 m in Hebei Plain are analyzed in the early morning of February 20 and February 21,2019.The results show that the duration of the two heavy fogs is short and the visibility rises obviously in the afternoon.We consider that the type of heavy fogs is mainly radiation fog.The fog occurred under the background of large-scale atmospheric subsidence,the high altitude circulation situation was stable,the middle wind speed was small,and the ground was in the front of high pressure,which was beneficial to the south of cold air to cause heavy fog weather in Hebei Plain.When the fog occurs,the temperature field above 1000 hPa has the weak thermal inversion or isotherm.and the temperature at 1000 hPa is 3-6℃higher than the surface temperature,which indicates that there is a strong inversion near the surface below 200 m.Stable atmospheric junction and lower boundary layer was in favor of the generation and maintenance of heavy fog.In addition,the humidity field is"lower wetter and upper drier"."Upper drier"which is beneficial to the radiation cooling in clear sky,and"lower wetter"is helpful to the saturation of near-surface air.In conclusion,sufficient water vapor after snow and radiation cooling formatted the strong fog on the 20th,while on the 21st,the mainly reason is the strong cooling near the ground.

关 键 词：河北平原 特强浓雾 环流形势 温湿场特征 

分 类 号：P458[天文地球—大气科学及气象学]