WITHDRAWN: Visibility trends in six cities of central China for the period 1974–2016

Abstract

The fine particulate matter pollution problems have been paid attention in central China since recent years. The pollution levels could be indicated by atmospheric visibility, which is inversely related to the optical extinction coefficient caused mostly by particle matters in China. In this study, the trends of visibilities in six cities in central China (Wuhan, Changsha, Hefei, Nanchang, Zhengzhou, and Taiyuan) were evaluated by using data from the National Climatic Data Center during 1974 to 2016. Four indexes were used, the days per year of daily visibility 19 km, the annual mean visibility, and the dry extinction coefficient. The annual and seasonal change trends of visibility for each city were analyzed by using a linear regression model. The analysis showed that annual visibility in all six cities has decreased, especially in Hefei, having a sharp visibility reduction of − 0.2380 km/year. Typically, visibility in all six cities is better in spring and summer than in autumn and winter. The minimum annual mean visibility was 6.07 km in Wuhan in 2014, while the maximum visibility was not more than 16.54 km in Nanchang in 1976 over the study period. Both values are much lower than the national mean visibility of 26 km. These data clearly show the worsening air quality in cities in central China, which is of strategic significance for the development of the central region.