Bai, Zishen;
Nahid, Mohajeri;
(2025)
Effects of extreme temperatures on spatial-temporal variations of NO2 in urban neighbourhoods in Greater London.
In:
Journal of Physics : Conference Series.
Institute of Physics (IoP)
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Abstract
Nitrogen dioxide (NO2), a common urban air pollutant, has a complex relationship with ambient temperature. While earlier studies found that rising temperatures lead to decrease NO2 concentrations, more recent observations suggest that extreme temperature may contribute to elevate NO2 levels. We use a low-cost sensor network to collect spatial-temporal NO2 and temperature data in Greater London. A time-series machine learning model (XG-Boost) is developed in incorporation with SHapley Additive exPlanations (SHAP), a machine learning interpreter, to explain the relations between NO2 and Temperature. SHAP analyses show that temperature has a negative contribution to the predicted NO2 concentrations within the range of 3°C to 25°C, while it contributes positively when temperature below 3°C or above 25°C. The reasons can be related to multiple factors: (i) atmospheric chemistry at extreme temperatures: faster release of NO2 from soils during extreme temperatures compared to its decomposition by sunlight, (ii) emissions from cities: increased use of motorised transport during extreme temperature. The study also shows that Local Climate Zone (LCZ) affect the temperature thresholds. LCZ5 (open midrise; upper temperature threshold is 23°C) may be more resilient to the effects of extreme temperatures on NO2 compared to LCZ2 (compact midrise; upper temperature threshold is 21°C). Increasing vegetation cover and improving urban ventilation can be considered effective strategies for reducing NO2 pollution. This study explores the effect of temperature extremes and LCZs on NO2, which provides a warning for climate change. Urban planners and policymakers should consider the potential risk of extreme temperature on future NO2 pollution.
| Type: | Proceedings paper |
|---|---|
| Title: | Effects of extreme temperatures on spatial-temporal variations of NO2 in urban neighbourhoods in Greater London |
| Event: | CISBAT 2025 |
| Location: | Lausanne, Switzerland |
| Dates: | 3 Sep 2025 - 5 Sep 2025 |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1088/1742-6596/3140/9/092003 |
| Publisher version: | http://doi.org/10.1088/1742-6596/3140/9/092003 |
| Language: | English |
| Additional information: | Content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of the Built Environment > Bartlett School Env, Energy and Resources |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10218707 |
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