08 Nov 2022
08 Nov 2022
Status: this preprint is open for discussion.

Coupled mesoscale-LES modeling of air quality in a polluted city using WRF-LES-Chem

Yuting Wang1, Yong-Feng Ma2, Domingo Muñoz-Esparza3, Jianing Dai4, Cathy W. Y. Li4, Pablo Lichtig4, Roy C. W. Tsang5, Chun-Ho Liu6, Tao Wang1, and Guy P. Brasseur1,4,7 Yuting Wang et al.
  • 1Department of Civil and Environmental Engineering, the Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
  • 2Department of Mechanics & Aerospace Engineering, Southern University of Science and Technology, Shenzhen, 518055, China
  • 3Research Applications Laboratory, National Center for Atmospheric Research, Boulder, CO 80301, USA
  • 4Max Planck Institute for Meteorology, 20146 Hamburg, Germany
  • 5Environmental Protection Department, Hong Kong
  • 6Department of Mechanical Engineering, The University of Hong Kong, Hong Kong
  • 7Atmospheric Chemistry Observation & Modeling Laboratory, National Center for Atmospheric Research, Boulder, CO 80301, USA

Abstract. To perform realistic high-resolution air quality modeling in a polluted urban area, the WRF (Weather Research and Forecasting) model is used with an embedded large-eddy simulation (LES) module and with online chemistry. As an illustration, a numerical experiment is conducted in the megacity Hong Kong, which is characterized by multi-type pollution sources as well as complex topography. The multi-resolution simulations from mesoscale to LES scales are evaluated by comparing to ozone sounding profiles and surface observations. The comparisons show that both mesoscale and LES simulations reproduce well the mean concentrations of the chemical species and their diurnal variations at the background stations. However, the mesoscale simulations largely underestimate the NOX concentrations and overestimate O3 at the roadside stations due to the coarse representation of the traffic emissions. The LES simulations improve the agreement with the measurements near the road traffic, and the LES with the highest spatial resolution (33.3 m) provides the best results. The LES simulations show more detailed structures in the spatial distributions of chemical species than the mesoscale simulations, highlighting the capability of LES to resolve high-resolution photochemical transformations in urban areas. Compared to the mesoscale model results, the LES simulations show similar evolutions in the profiles of the chemical species as a function of the boundary layer development over a diurnal cycle.

Yuting Wang et al.

Status: open (until 03 Jan 2023)

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Yuting Wang et al.

Yuting Wang et al.


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Short summary
Air quality in urban areas is difficult to simulate in coarse resolution models. This work exploits the WRF (Weather Research and Forecasting) model coupled with a large-eddy simulation (LES) component and with online chemistry to perform very high resolution (33.3 m) simulations for air quality in a large city. The evaluation of the simulations with observations shows that increased model resolution improves the representation of the chemical species near the pollution sources.