Aerosol light absorption plays a crucial role in regulating the heat balance between the atmosphere and the Earth's surface. This happens through two main mechanisms: the aerosol direct effect, where aerosols absorb solar radiation, and the aerosol indirect effect, which involves aerosols acting as cloud condensation nuclei and ice nuclei. These effects not only influence local climates but can also lead to climate changes on a global scale. Furthermore, the interactions between aerosols, radiation, and photolysis add complexity to their impact on haze formation.
A recent study published in the journal Proceedings of the National Academy of Sciences (PNAS) revealed the role of light-absorbing aerosols in wintertime haze formation.
In this study, the researchers developed a radiative transfer model that comprehensively considers the multi-component, full-size distribution of aerosols, coupled it with a regional atmospheric chemical transport model, and combined observational data to quantitatively analyze the impact of light-absorbing aerosols-radiation-photolysis interactions on winter haze formation at a large scale.
"The findings indicate that previous studies may have overestimated the positive role of aerosol light absorption in haze formation," said Prof. LI. "This offers new insights into how light-absorbing aerosols influence atmospheric physicochemical processes."
In terms of atmospheric physical mechanisms, previous studies have indicated that light-absorbing aerosols worsen pollution at the urban scale. However, when considering these aerosols on a larger scale, the researchers observe uneven heating rates in the vertical direction. The highest heating rate occurs at the top of the boundary layer, which creates a "warm bubble" effect. This effect intensifies the upward movement of air in polluted areas while promoting the downward movement of air in cleaner areas, ultimately leading to a reduction in PM2.5 concentrations. Additionally, light-absorbing aerosols decrease atmospheric oxidation, which suppresses the formation of secondary aerosols, further contributing to the decrease in PM2.5 levels.
The study is crucial for revealing the mechanisms of light-absorbing aerosols within the climate system, providing key data for climate models, and offering a scientific basis for strategies to reduce aerosol emissions and improve air quality.
The study was led by Prof. LI Guohui from the Institute of Earth Environment of the Chinese Academy of Sciences (CAS) in collaboration with researchers from Stanford University, the California Institute of Technology, Xi'an Jiaotong University, and the Institute of Atmospheric Physics of CAS.
