北京地区一次典型大雾天气过程的边界层特征分析  

Analysis on Characteristic of Atmospheric Boundary Layer during a Typical Heavy Fog Process in Beijing Area

作　　者：刘熙明[1,2,3] 胡非[3] 邹海波[1] 曹晓彦[4] 窦军霞[4] 

机构地区：[1]江西省气象科学研究所,江西南昌330046 [2]江西省气候中心,江西南昌330046 [3]中国科学院大气物理研究所,北京100029 [4]中国气象局北京城市气象研究所,北京100089

出　　处：《高原气象》2010年第5期1174-1182,共9页Plateau Meteorology

基　　金：国家自然科学基金项目(40965001);2008年度城市气象科学研究基金项目(UMRF200810);江西省2009年度自然科学基金项目;中国气象科学研究院灾害天气国家重点实验室基金项目(2009LASW-A02)共同资助

摘　　要：利用中国科学院大气物理研究所325 m铁塔15层风、温、湿梯度观测资料和3层超声资料,对2002年12月1-4日发生在北京地区的持续大雾天气过程进行近地面层大气边界层特征分析。结果表明,近地面大气边界层较大的相对湿度（〉70%）、较小的风速（〈3.0 m·s^-1）和风速垂直切变（〈0.02 s^-1）、稳定的层结结构以及较低的气温是北京持续大雾天气形成的主要原因。冷空气的侵入使得边界层相对湿度迅速减小,风速和风速垂直切变增大,破坏近地面大气边界层的结构,导致大雾的消散。分析还发现,大雾的维持与消散主要受风场等动力因素的影响,热力层结是大雾维持和消散的必要条件。冷空气的侵入自上而下影响平均风场,而对湍流风场的影响则是自下而上的。尺度分析结果表明,大雾期间,近地面边界层内中尺度动量通量和感热通量都大于湍流尺度的,中尺度动量通量与平均风速基本呈反相关;冷空气的侵入使得湍流通量显著加强,是导致大雾天气消失的主要原因。Based on the wind,temperature and relative humidity gradient data and turbulent data observed at 325 m Meteorological Tower of Institute of Atmospheric Physics,Chinese Academy of Sciences,the characteristics of atmospheric boundary layer（ABL） near the surface during a typical heavy fog process in Beijing area from 1 to 4 December 2002 are discussed.The results show that larger relative humidity （〉70%）, smaller wind speed（〈3.0 m·s^-1）,smaller vertical wind shear（〈0.02 s^-1）,stable stratification structure and lower temperature are the main factors of formation for persistent heavy fog in Beijing area.The invasion of cold air results in the decrease of relative humidity,the increase of wind speed and vertical wind shear,which destroys the structure of ABL near the surface,and eventually causes the disappearance of heavy fog.The results also show that the dynamic elements,such as wind field,play the key roles for the persistence and disappearance of heavy fog,while the thermodynamic stratification is the essential condition of the persistence and disappearance of heavy fog.The cold air influences on the mean wind field from upper to lower levels,while it influences on the turbulent wind field from lower to upper levels.The results of dimensional analysis reveal that during the heavy fog process,in the ABL near surface the mesoscale momentum flux and sensible heat flux are larger than the turbulent momentum flux and sensible heat flux,and the mesoscale momentum flux is negatively correlated to the mean wind speed.The invasion of cold air increases the turbulent flux,which is the main cause of heavy fog disappearance.

关 键 词：北京地区 大雾 城市边界层 湍流 中尺度通量 

分 类 号：P458.3[天文地球—大气科学及气象学]