Abstract
Aerosols can affect vertical thermal structure during heavily polluted episodes (HPEs). Here, we selected four typical HPEs in 2018, which were further subdivided into dust and haze events. The vertical distribution of aerosols extinction coefficient (EC) and variations in columnar optical properties were investigated based on sun-photometer and Lidar observation at an urban site in Beijing. The vertical characteristics in shortwave radiative heating rate (HR) of aerosols were studied using NASA/Goddard radiative transfer model along with observational data. In the haze episode, EC layer is less than 1.5 km and shows strong scattering, with single-scattering albedo (SSA440nm) of ~0.97. The heating effects are observed at the middle and upper atmosphere, and slight heating effects are found at the lower layer. The mean HR within 1.5 km can be up to 16.3 K day−1 with EC of 1.27 km−1, whereas the HR within 0.5 km is only 1.3 K day−1. In the dust episode, dust aerosols present the absorption with SSA440nm of ~0.88, which would heat the lower atmosphere to promote vertical turbulence, and the height of EC layer can be up to 2.0–3.5 km. In addition, the strong heating effects of dust layer produced cooling effects near the surface. Therefore, the accurate measurement of aerosols optical properties in HPEs is of great significance for modeling aerosols direct radiative effects.
Highlights
As an important part of the Earth–atmosphere system, aerosols play a vital role in the global climate change and can influence the efficiency of solar radiation production, eco-environment, and population health [1,2,3,4,5]
Considering the effects of aerosols on solar radiation, we selected cases which the maximum values occurred on daytime as much as possible
We combined with continuous aerosol observational data to avoid aerosol opMoreover, we combined with continuous aerosol observational data to avoid aerosol optical tical data missing caused by cloud or precipitation [57]
Summary
As an important part of the Earth–atmosphere system, aerosols play a vital role in the global climate change and can influence the efficiency of solar radiation production, eco-environment, and population health [1,2,3,4,5]. Developed a radiative transfer model (Fu–Liou radiation model) to evaluate the influence of absorbing gases, aerosols, and clouds in the atmosphere, and reached an important conclusion that aerosols lead to an increase in the atmospheric absorption and a reduction in the solar flux that can be absorbed at the Earth’s surface. We used ground-based observations, remote sensing and model simulations to investigate the role of aerosol shortwave radiative effects during haze and dust pollution episodes that occurred in spring, summer, and autumn in Beijing.
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