Assessing Transboundary‐Local Aerosols Interaction Over Complex Terrain Using a Doppler LiDAR Network

Abstract

Transboundary‐local aerosols interaction requires to be comprehensively understood in urban air quality research. A year‐long intensive observation of the atmospheric boundary layer (ABL) at multiple sites in Hong Kong was conducted using a four‐Doppler Light Detection and Ranging (LiDAR) network with different scanning modes. Results show that heterogeneity of the ABL in terms of mixing layer height and wind shear was induced by orographic topography. Interaction between local and advected aerosol layers during a transboundary air pollution (TAP) episode was identified by the network. During TAP episode, downward transport of transboundary aerosol relied on small scale eddies with weak wind speed in nighttime, while the transport of surface local aerosol to upper level was the dominated process in daytime, but the heterogeneity of the ABL affected by terrain determined the capacity of the mixing, eventually resulting in the opposite transport direction of aerosols in the transboundary‐local aerosols interaction.

Observations of vertical velocity from a Doppler LiDAR in the urban area of Hong Kong

“…The Doppler LiDAR installed at King's Park (Yim, 2020) is shown in Figure 1(b). It is a Halo Photonics 1.5‐μm pulsed Doppler instrument, which has been used in studies exploring the characteristics of the planetary boundary layer in the tropical and mid‐latitude environments (Yang et al ., 2019; Huang et al ., 2020, 2021a,b, 2022; Yim, 2020; Yim and Tao, 2022). The instrument was fixed on a concrete foundation in a flat grass field, at an altitude of 65m amsl.…”

Investigating the Interaction Between Transboundary Haze and Planetary Boundary Layer in Singapore

“…In addition to localized air pollution, transboundary air pollution has emerged as a crucial factor exacerbating air pollution on global (Holloway et al., 2003), regional (Gu & Yim, 2016; Hou et al., 2019), and local scales (Tong et al., 2018; Huang, Li, et al., 2021). Particularly, transboundary haze stemming from biomass burning has been a prominent issue throughout Southeast Asia (Hansen et al., 2019).…”

Assessing the Spatiotemporal Characteristics, Factor Importance, and Health Impacts of Air Pollution in Seoul by Integrating Machine Learning into Land-Use Regression Modeling at High Spatiotemporal Resolutions

“…While previous studies focused on improving model performance, few of them attempted to evaluate the contribution of different factors on air pollutants, which is particularly important for cities with air pollution influenced not only by their local sources but also by transboundary pollution from neighboring regions. , To understand air pollutant concentration effectively, contributions of different driving factors (i.e., emission sources and meteorological factors) , to air quality should be analyzed comprehensively. For example, numerous studies reported that the East Asian region including South Korea has been affected by transboundary air pollution , that can be driven by favorable meteorological conditions for long-range air pollutant transport.…”