[Construction and Application of Vertical Diffusion Index for Analyzing Weather During Pollution Events in Tianjin]

Based on temperature and wind speed data from the 255 meter tall meteorological tower, the characteristics of atmospheric stability were analyzed in Tianjin, with the vertical diffusion index β and φ constructed by atmospheric chemical models. This provided information to use the vertical dispersion analysis method to forecast pollution from weather data. The results show that the comprehensive use of atmospheric stability and the vertical diffusion index can provide a better pollution forecast. When the atmospheric stability was D from 07:00-08:00 and 18:00-20:00, compared to when atmospheric stability was C, the probability of heavy pollution weather increased by 10 times. If the vertical diffusion index β and wind speed index were used to forecast heavy pollution, the accuracy rate was 67% higher than when using the single wind speed index. The coefficient between vertical diffusion index φ and PM_2.5 mass concentration was 0.8.When the vertical diffusion index φ was less than 0.52, the probability of heavy pollution was 75%, identifying 59% of heavy pollution events.