Development and application of a street-level meteorology and pollutant tracking system (S-TRACK)

Huan Zhang,Jingyue Mo,Shuhua Lu,Xu Wang,Jingwei Ni,Sunling Gong,Huabing Ke,Lei Zhang,Yaqiang Wang,Lixin Shi,Jianjun He

doi:10.5194/acp-22-2221-2022

Abstract

Abstract. A multi-model simulation system for street-level circulation and pollutant tracking (S-TRACK) has been developed by integrating the Weather Research and Forecasting (WRF), the STAR-CCM+ (computational fluid dynamics model – CFD), and the Flexible Particle (FLEXPART) models. The winter wind environmental characteristics and the potential contribution of traffic sources to nearby receptor sites in a city district of China are analysed with the system for January 2019. It is found that complex building layouts change the structure of the wind field and thus have an impact on the transport of pollutants. The wind speed inside the building block is lower than the background wind speed due to the dragging effect of dense buildings. Ventilation is better when the dominant airflow is in the same direction as the building layout. Influenced by the building layout, the local circulations show that the windward side of the building is mostly the divergence zone, and the leeward side is mostly the convergence zone, which is more obvious for high buildings. With the hypothesis that the traffic sources are uniformly distributed on each road and with identical traffic intensity, the potential contribution ratios (PCRs) of four traffic sources to certain specific sites under the influence of the street-level circulations are estimated with the method of residence time analysis. It is found that the contribution ratio varies with the height of the receptor site. As a result of the generally upward motion in the airflow, the position with the greatest PCR from the four road traffic sources is located at a certain height which is commonly influenced by the distance of this location from the traffic source and the background wind field (about 15 m in this study). The potential contribution of a road to one of the receptor sites is also investigated under different wind directions. The established system and the results can be used to understand the characteristics of urban wind environment and to help the air pollution control planning in urban areas.

Highlights

In recent decades, with the continuous development of urban construction in China, urban environmental problems have become increasingly serious and attracted widespread attention
The performance of the Weather Research and Forecasting (WRF) model to simulate meteorological elements is an important basis for the STAR-CCM+ and FLEXPART simulations
The hourly meteorological data for January 2019 obtained from the innermost nested simulation of the WRF model are selected to compare with observation data to verify the WRF model

Summary

Introduction

With the continuous development of urban construction in China, urban environmental problems have become increasingly serious and attracted widespread attention. According to the 2019 China Ecological Environment Status Bulletin, 180 of 337 cities at the prefecture level exceeded ambient air quality standards. The complex building layouts and differences in thermal structures within cities lead to extremely complicated meteorological characteristics and pollutant transport in urban areas (Aynsley, 1989; Fernando et al, 2010; Lei et al, 2012). Though the transport of atmospheric pollution in urban areas is widely studied, tracking the sources of pollutants at the street level is still lacking due to limitations in research methods. H. Zhang et al.: Development and application of S-TRACK

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Results

Conclusion