Uncertainty analysis of spatiotemporal characteristics of haze pollution from 1961 to 2017 in China

Abstract

The definition of haze day is still controversial, and there are different data sources for haze data in China. This study analyzes the uncertainty of haze data in China, which is a prerequisite for studying haze trends. The overall trends defined by different approaches were relatively consistent, but the average values were different. The annual number of haze days defined by visibility and relative humidity was higher than the number defined by manual observation. The correlation coefficient between the two datasets for the whole country was 0.92, and ranged from 0.7 to 0.9 for different regions. The similarity between the trends of haze days by different approaches was greater in the Yangtze River Delta region and the Pearl River Delta region than in the Southwest Region. Limited impact of relative humidity on the trends of haze days was detected in China and different regions. The influence of station screening was also investigated. Station screening had no effect on the annual average number of haze days and the long-term trend. Based on the above analysis, the haze data defined by visibility and relative humidity were chosen to study the spatial and temporal distributions for China. In terms of seasons, haze days were most frequent in winter and least frequent in summer. Except for the Northwest region, the number of haze days increased noticeably after 1980. Our results can further deepen the understanding of the characteristics of haze pollution, and support the study of the causes of haze pollution in China.