- Analysis of temperature and moisture structure and turbulence characteristics of a smog and haze weather process in Tianjin
- Abstract：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 PM2.5, 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.