Abstract
Transported pollution plays an important role in the atmospheric environment of eastern China. This study analyzed the characteristics of surface winds at different air quality levels using meteorological station observations of both wind and mass concentrations of particulate matter with aerodynamic diameters <2.5 μm (PM2.5) over Hong Kong and Beijing. In recent decades, wind directions at the surface exhibit a similar pattern for both good and poor air quality levels at all three stations, indicating a weak relationship between surface winds and air quality in Hong Kong. However, winds at a height of 1–2 km govern pollution accumulation. This dominant role is illustrated by a sudden change in wind direction within this layer and a simultaneous pollution accumulation stage on 8 January 2014. The controlling influence of winds at 1–2 km on both the deterioration and improvement of air quality is also supported by a distinct vertical wind distribution for all 21 monotonic increasing stages and 17 decreasing stages of PM2.5. In contrast, air pollution is transported to Beijing throughout the atmospheric layer that extends from the surface to a height of more than 3 km. This key difference may be due to variations in meteorology, topography, and emission sources between Hong Kong and Beijing. The results that layer of 1–2 km in Hong Kong and of surface to 3 km in Beijing is the height where pollution transport is most likely to occur are critical for forecasting severe haze episodes in eastern China.
Highlights
Eastern China has been one of the most polluted regions in the world during recent decades
Simulation of a severe haze episode showed that PM2.5 concentrations in the North China Plain (NCP) were substantially influenced by transported pollutions from the Yangtze River Delta (YRD)
Statistical vertical distribution in pollution transportation in Hong Kong and Beijing may represent the typical pattern in the regions of YRD and NCP
Summary
Eastern China has been one of the most polluted regions in the world during recent decades. Simulation of a severe haze episode showed that PM2.5 (particulate matter with aerodynamic diameters < 2.5 μm) concentrations in the North China Plain (NCP) were substantially influenced by transported pollutions from the Yangtze River Delta (YRD). Based on aircraft measurements, Tian et al (2019) [6] indicate that black carbon is enhanced at 400–800 m by regional transport over Beijing It seems the transport pathway in northern China has a wider range in height. Statistical vertical distribution in pollution transportation in Hong Kong and Beijing may represent the typical pattern in the regions of YRD and NCP. This statistical analysis is critical for elucidating the transport mechanisms and formation of severe air pollution in Hong Kong and Beijing. The results will be helpful for air quality forecasts in eastern China, where there is a high proportion of transported pollutants
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