Details
| Original language | English |
|---|---|
| Journal | Quarterly Journal of the Royal Meteorological Society |
| Publication status | E-pub ahead of print - 10 Mar 2025 |
Abstract
While the positive effect of trees on thermal comfort is well-established, particularly in urban street canyons, their impact on air quality remains questionable, especially in the case of pollutants emitted by heavy traffic at the pedestrian level. Complex microscale models of an urban boundary layer with a high spatial resolution (down to 1 m) enable a deeper understanding of most processes at street-level scale and can simulate selected variables related to air quality and bio-meteorology with high precision and fidelity. In this study, scenarios with different percentages of tree coverage of two streets were simulated under different atmospheric stratifications to investigate the problem. Real geography and quasi-real meteorology were used as a background. Results of the Parallelized Large-eddy Simulation Model (PALM) model simulations, which utilised a large-eddy simulation (LES) core, showed the spatio-temporal variability of the thermal comfort and dust concentration at the pedestrian level. The findings indicate that the effect of trees on the local microclimate is crucial and complex and cannot be omitted during the planning of urban mitigation measures. The study demonstrates a notable improvement in thermal comfort, with a significant decrease in the thermal index in shaded areas beneath trees during the hottest part of the day, as well as a cooling effect of urban greenery just after sunset. However, the analysis also revealed a significant downside: in narrower streets, (Formula presented.) concentrations increased by more than 100% compared with tree-free scenarios. The slowdown and vertical shift of the primary vortex within the street caused by the trees can mostly explain the changes in pollution dispersion. This indicates a potential trade-off between thermal comfort and air quality in densely built urban environments.
Keywords
- air quality, atmospheric stratification, large-eddy simulation, microclimate modelling, scenarios, thermal comfort, urban boundary layer, urban street canyon
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)
- Atmospheric Science
Sustainable Development Goals
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In: Quarterly Journal of the Royal Meteorological Society, 10.03.2025.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Analysis of the complex role of trees in street canyons using a large-eddy simulation model
AU - Řezníček, Hynek
AU - Geletič, Jan
AU - Belda, Michal
AU - Beneš, Luděk
AU - Bureš, Martin
AU - Eben, Kryštof
AU - Fuka, Vladimír
AU - Krč, Pavel
AU - Michálek, Petr
AU - Patiño, William
AU - Radović, Jelena
AU - Sühring, Matthias
AU - Vlček, Ondřej
AU - Resler, Jaroslav
N1 - Publisher Copyright: © 2025 The Author(s). Quarterly Journal of the Royal Meteorological Society published by John Wiley & Sons Ltd on behalf of Royal Meteorological Society.
PY - 2025/3/10
Y1 - 2025/3/10
N2 - While the positive effect of trees on thermal comfort is well-established, particularly in urban street canyons, their impact on air quality remains questionable, especially in the case of pollutants emitted by heavy traffic at the pedestrian level. Complex microscale models of an urban boundary layer with a high spatial resolution (down to 1 m) enable a deeper understanding of most processes at street-level scale and can simulate selected variables related to air quality and bio-meteorology with high precision and fidelity. In this study, scenarios with different percentages of tree coverage of two streets were simulated under different atmospheric stratifications to investigate the problem. Real geography and quasi-real meteorology were used as a background. Results of the Parallelized Large-eddy Simulation Model (PALM) model simulations, which utilised a large-eddy simulation (LES) core, showed the spatio-temporal variability of the thermal comfort and dust concentration at the pedestrian level. The findings indicate that the effect of trees on the local microclimate is crucial and complex and cannot be omitted during the planning of urban mitigation measures. The study demonstrates a notable improvement in thermal comfort, with a significant decrease in the thermal index in shaded areas beneath trees during the hottest part of the day, as well as a cooling effect of urban greenery just after sunset. However, the analysis also revealed a significant downside: in narrower streets, (Formula presented.) concentrations increased by more than 100% compared with tree-free scenarios. The slowdown and vertical shift of the primary vortex within the street caused by the trees can mostly explain the changes in pollution dispersion. This indicates a potential trade-off between thermal comfort and air quality in densely built urban environments.
AB - While the positive effect of trees on thermal comfort is well-established, particularly in urban street canyons, their impact on air quality remains questionable, especially in the case of pollutants emitted by heavy traffic at the pedestrian level. Complex microscale models of an urban boundary layer with a high spatial resolution (down to 1 m) enable a deeper understanding of most processes at street-level scale and can simulate selected variables related to air quality and bio-meteorology with high precision and fidelity. In this study, scenarios with different percentages of tree coverage of two streets were simulated under different atmospheric stratifications to investigate the problem. Real geography and quasi-real meteorology were used as a background. Results of the Parallelized Large-eddy Simulation Model (PALM) model simulations, which utilised a large-eddy simulation (LES) core, showed the spatio-temporal variability of the thermal comfort and dust concentration at the pedestrian level. The findings indicate that the effect of trees on the local microclimate is crucial and complex and cannot be omitted during the planning of urban mitigation measures. The study demonstrates a notable improvement in thermal comfort, with a significant decrease in the thermal index in shaded areas beneath trees during the hottest part of the day, as well as a cooling effect of urban greenery just after sunset. However, the analysis also revealed a significant downside: in narrower streets, (Formula presented.) concentrations increased by more than 100% compared with tree-free scenarios. The slowdown and vertical shift of the primary vortex within the street caused by the trees can mostly explain the changes in pollution dispersion. This indicates a potential trade-off between thermal comfort and air quality in densely built urban environments.
KW - air quality
KW - atmospheric stratification
KW - large-eddy simulation
KW - microclimate modelling
KW - scenarios
KW - thermal comfort
KW - urban boundary layer
KW - urban street canyon
UR - http://www.scopus.com/inward/record.url?scp=105000214376&partnerID=8YFLogxK
U2 - 10.1002/qj.4954
DO - 10.1002/qj.4954
M3 - Article
AN - SCOPUS:105000214376
JO - Quarterly Journal of the Royal Meteorological Society
JF - Quarterly Journal of the Royal Meteorological Society
SN - 0035-9009
ER -