[Relationship Between Atmospheric Visibility and PM_2.5 Concentrations and Distributions]

Area of Science:

• Atmospheric Science
• Environmental Science
• Air Quality Research

Context:

• Analysis of monitoring data to understand the interplay between relative humidity (RH), visibility, and fine particulate matter (PM2.5) concentrations.
• Investigating regional variations in PM2.5 extinction efficiency and the impact of RH on visibility across different Chinese locations.

Purpose:

• To propose a linear relationship model between the extinction coefficient and PM2.5 concentrations under varying RH conditions.
• To quantify the influence of RH on visibility reduction in key regions like Beijing and Guangzhou.
• To analyze long-term trends and regional disparities in PM2.5 concentrations across China.

Summary:

• A strong linear relationship was identified between the extinction coefficient and PM2.5 concentrations, with high correlation coefficients (0.75-0.9) observed between 40%-90% RH in Central and Eastern China.
• PM2.5 extinction efficiency is notably higher in Beijing, the Yangtze River Delta, and Sichuan. The impact of RH on visibility reduction varies regionally, with different RH thresholds triggering significant visibility decrease.
• Historical data indicate rising national PM2.5 concentrations since 1980, with persistently higher levels in North China. Beijing experienced significant PM2.5 variations linked to heating and showed a complex trend from 1997-2012.

Impact:

• Provides a predictive model for air quality assessment and visibility forecasting based on RH and PM2.5.
• Highlights regional vulnerabilities to air pollution and the specific role of humidity in visibility impairment.
• Informs environmental policy and public health strategies by detailing long-term air quality trends and geographical pollution hotspots.