Visibility Variation in Zhengzhou from 2008–2017

Abstract

Visibility is closely related to air quality and is therefore a source of concern. Using data from the National Basic Weather Station (NBWS), this study measured visibility variation in Zhengzhou from 2008 to 2017. The effects of PM2.5 and meteorological parameters on visibility were also assessed. Results indicated that the mean annual visibility fluctuated between 8.07 km and 14.02 km, decreasing during the period from 2008 to 2013 and then increasing slightly after 2013. The seasonal mean visibility was 11.69 km in spring (the highest value), 11.37 km in summer, 9.42 km in autumn, and 8.98 km in winter (the lowest value). The mean annual concentrations of PM2.5 from 2015 to 2017 were 90.83 μg m-3, 79.89 μg m-3, and 66.69 μg m-3, respectively. These were 159.51%, 128.26%, and 90.54% higher than 35 μg m-3 of the second grade of China National Ambient Air Quality Standards (CNAAQS). Additionally, direct radiation, total radiation, temperature, and relative humidity were positively correlated with visibility, whereas PM2.5 mass concentration, scattered radiation, and wind velocity were negatively correlated with visibility. Further research is needed to analyse the effect of PM2.5 on visibility and the mechanism through which this occurs.