Aerosol light absorption regulates the heat balance between the atmosphere and the Earth's surface by absorbing solar radiation (aerosol direct effect), and simultaneously affect the formation and characteristics of clouds and precipitation as cloud condensation nuclei and ice nuclei (aerosol indirect effect). The direct and indirect radiative effects of light-absorbing aerosols not only impact local climates but may also trigger climate changes on a global scale. Moreover, the interactions between aerosols, radiation, and photolysis further complicate their impact on the haze formation.

In-depth research on light-absorbing aerosols is crucial for revealing their mechanisms 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. This research holds profound significance for a comprehensive understanding of the atmospheric environment and climate systems.

The research, led by Prof. LI Guohui from the Institute of Earth Environment, Chinese Academy of Sciences, collaborated with researchers from Stanford University, the California Institute of Technology, Xi'an Jiaotong University, and the Institute of Atmospheric Physics, Chinese Academy of Sciences, was published in the journal Proceedings of the National Academy of Sciences on December 23, 2024.

They 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 study's findings suggest that the positive contribution of aerosol light absorption to haze formation may have been overestimated in previous studies, and it proposes new insights into the impact of light absorbing aerosols on atmospheric physicochemical processes.” said Prof. Li.

In terms of atmospheric physical mechanisms, unlike previous findings that light absorbing aerosols exacerbate pollution at the urban scale, considering light absorbing aerosols at a larger scale results in uneven heating rates in the vertical direction, with the maximum heating rate occurring at the top of the boundary layer , which triggers a "warm bubble" effect that intensifies the upward movement in polluted areas and the downward movement in clean areas, thereby reducing PM_2.5 concentrations. Also, light absorbing aerosols lead to a reduction in atmospheric oxidation, suppressing the formation of secondary aerosols, further resulting in a decrease in PM_2.5 concentrations.

The study emphasizes that when formulating mitigation strategies to alleviate the severity of winter haze events, the unique effects of light absorbing aerosols must be fully considered, providing new ideas for air pollution control and scientific support for the development of climate change adaptation and mitigation measures.