天津一次雾-霾天气过程的近地层温湿结构和湍流特征分析

采用地面大气能见度、PM_(2.5)质量浓度、梯度气象资料、塔上湍流观测资料等多种资料及后向轨迹方法,分析近地层温湿结构和湍流特征对2016年12月16日—21日天津地区一次严重持续雾霾天气演变过程的影响.结果表明,本次雾霾天气过程可以明显的分为霾、雾的生成和发展、雾成熟和雾霾消散等4个阶段,近地层温度、相对湿度和风的垂直分布及湍流特征对各阶段的雾-霾转化起到了重要作用.霾生成期间,偏南气流盛行,地面风速降低,RH不断增大,湍流不活跃;地面辐射降温引发了近地层内显著的强逆温,并导致RH由地面到高空逐渐增大,有利于雾的生成和发展;感热通量和潜热通量爆发式增长,导致逆温层瓦解,雾顶继续抬升,雾进入成熟阶段,湍流活动减弱;受西北气流影响,湍流活跃,高空的干冷气团向下取代地面暖湿气团,结束本次雾霾天气过程.采用近地层温湿结构和湍流特征资料,可用于雾-霾天气的演变及其转化过程精细分析.

Analysis of temperature and moisture structure and turbulence characteristics of a smog and haze weather process in Tianjin

The influence of the vertical structure for temperature and humidity in the boundary layer and the characteristics of turbulence on the evolution of a severe persistent haze-fog event in Tianjin during December 16 to 21 in 2016 was discussed in this study, by using theobserved surface mass concentration of PM_2.5, visibility, gradient meteorological data,turbulence observation data on the tower, as well as the backward trajectory method. The results showed that the haze eventcouldbe divided into four stages, i.e.,the formation of fog-haze, the development of fog-haze, the mature of fog and the dissipation of fog-haze. The vertical distribution of temperature, relative humidity and wind in the surface layer, as well as the characteristics of turbulence played an important role in the fog-haze transformation in each stage.During the formation stage, the southerly wind prevailed in this region, with decreases in the wind speed near the surface, increases in RH, and the suppressed turbulence.The reduction in the surface temperature due to decreases in solar radiation could lead to a strong inversion in the surface layer and the gradual increase in RH from the ground to the upper air, which was conduciveto the formation and development of the fog. In the mature stage, the sensible and latent heat flux exhibited explosive growth, leading to the collapse of the inversion layer, the lifting of the fog top layer, and the weakened turbulence. With the influence of northwest wind, the turbulence became more active, the dry cold air mass at high altitude moved downward, and replaced the warm and wet air mass near the surface, and the haze-fog process ended.By using the vertical data of temperature and moisture, as well as the turbulence data, the evolution and transformation of fog-hazeevent can be analyzed more accurately.