Synoptic pattern and planetary boundary layer structure associated with aerosol pollution during winter in Beijing,...

Area of Science:

• Atmospheric Science
• Environmental Science
• Air Quality Research

Background:

• Planetary Boundary Layer (PBL) dynamics significantly influence air quality, particularly PM2.5 pollution.
• Winter pollution in Beijing is complex, with limited understanding of synoptic forcings, PBL processes, and their interactions.
• Long-term PBL observations in Beijing during winter are scarce, hindering comprehensive analysis.

Purpose of the Study:

• To investigate the complex relationships between large-scale synoptic patterns, local PBL structures, and PM2.5 pollution in Beijing during winter.
• To quantify the impact of PBL height and synoptic patterns on daily PM2.5 variations.
• To differentiate the contributions of local emissions versus regional transport to severe pollution events.

Main Methods:

• Utilized a combination of aerosol measurements, meteorological observations, radiosonde data, and reanalysis datasets.
• Performed long-term 3D meteorological simulations and validated them with observational data.
• Employed meteorology-chemistry coupled simulations and objective analysis of geopotential height fields to identify synoptic patterns.

Main Results:

• A significant inverse correlation was found between daily boundary layer height (BLH) and PM2.5 concentration.
• Low BLH days were often associated with strong elevated thermal inversion layers, exacerbating pollution.
• Two dominant synoptic patterns were identified: one linked to local emissions under weak northwesterly winds, and another involving southerly transport of pollutants.

Conclusions:

• PBL structure, particularly BLH and thermal inversions, plays a critical role in modulating winter PM2.5 pollution in Beijing.
• Synoptic patterns significantly influence pollution levels, with southerly transport contributing substantially (approx. 56%) to Beijing's PM2.5.
• Understanding multiscale meteorological factors is crucial for effective air pollution control strategies in Beijing.