[Differences in Pollution Characteristics Under the Southerly and Easterly Wind in Beijing].

Area of Science:

• Atmospheric Science
• Environmental Science
• Air Quality Research

Background:

• Particulate Matter (PM2.5) pollution is a significant environmental challenge in many urban areas.
• Understanding the influence of meteorological factors and wind direction on PM2.5 concentrations is crucial for effective air quality management.

Purpose of the Study:

• To analyze hourly meteorological factors and PM2.5 concentrations in Beijing from 2014-2019.
• To investigate the characteristics of prevailing wind directions associated with pollution events.
• To identify long-term trends in pollution occurrence related to wind patterns.

Main Methods:

• Analysis of hourly meteorological data and PM2.5 concentrations in Beijing (2014-2019).
• Statistical analysis to determine pollution probability under different wind directions (southerly, easterly) and seasons.
• Correlation analysis between meteorological factors (visibility, mixing layer height, wind speed, humidity, dew point) and PM2.5 levels.

Main Results:

• 67% of Beijing's pollution events were associated with southerly and easterly winds, with winter being the most polluted season.
• Pollution probability was higher under easterly winds compared to the more frequent southerly winds, particularly in spring.
• A significant annual decrease in pollution probability (4.6%-8.0% for southerly, 5.5%-7.9% for easterly) was observed, indicating reduced moderate and severe pollution levels.

Conclusions:

• Atmospheric conditions under southerly winds offer slightly better pollutant dispersal than easterly winds.
• Increased atmospheric water content under easterly winds promotes pollution persistence and worsening.
• Beijing's pollution exhibits an 'easterly wind type' in spring, summer, and autumn, but remains a 'southerly wind type' in winter, with southerly winds potentially exacerbating PM2.5 during winter heating.