The effect of wind speed on hazy weather from the long-term trend of low visibility: A case study in the Beijing-Tianjin-Hebei region, China

Abstract

To account for the short observation time for PM2.5 determinations in China, this study developed a low visibility-wind speed relationship logistic regression model based on long-term visibility data from 1981 to 2015 as a proxy to analyze the effect of wind speed on hazy weather on long time scales. The visibility improves as the wind speed increases, and the most significant visibility improvement occurs at wind speeds of 3–5 m/s. When the wind speed is greater than 10 m/s, the visibility does not respond significantly. This study also identified “difficult-to-disperse areas” (DDAs) within the BTH region, where the visibility improves less than in other areas under increasing wind speeds. When the wind speed increases from 3.4 m/s to 8 m/s, the visibility improvement in the DDAs ranges from 0 to 3.25 km. In contrast, the visibility in the “easy-to-disperse areas” (EDAs) can be improved by approximately 2–5.5 km, causing the visibility in some areas to reach more than 10 km. The increase in the number of hazy days caused by industrial production in the DDAs lagged during 2009–2013, and the hard-to-disperse effect in the DDAs was a consequence of the accumulation of industrial pollution over 10 years. Thus, atmospheric treatment may require more than 10 years of continuous treatment. The simulation results before and after air pollution control show that the visibility improvement ranges from 0.26 to 5.37 km at the same wind speed, confirming the effectiveness of air pollution control in China since 2013. Both the deterioration and the improvement in the air quality are the result of a period of time, and although visibility has improved in recent years, hazy weather management requires preparation for a long-term battle.