The ZiCOS-M CO<sub>2</sub> sensor network: measurement performance and CO<sub>2</sub> variability across Zurich

<p>As a component of the ICOS Cities project, a “mid-cost” NDIR (nondispersive infrared) <span class="inline-formula">CO<sub>2</sub></span> sensor network was deployed across the city of Zurich (Switzerland), known as ZiCOS-M. The network was operational betwe...

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Main Authors: S. K. Grange, P. Rubli, A. Fischer, D. Brunner, C. Hueglin, L. Emmenegger
Format: Article
Language:English
Published: Copernicus Publications 2025-03-01
Series:Atmospheric Chemistry and Physics
Online Access:https://acp.copernicus.org/articles/25/2781/2025/acp-25-2781-2025.pdf
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author S. K. Grange
S. K. Grange
S. K. Grange
P. Rubli
A. Fischer
D. Brunner
C. Hueglin
L. Emmenegger
author_facet S. K. Grange
S. K. Grange
S. K. Grange
P. Rubli
A. Fischer
D. Brunner
C. Hueglin
L. Emmenegger
author_sort S. K. Grange
collection DOAJ
description <p>As a component of the ICOS Cities project, a “mid-cost” NDIR (nondispersive infrared) <span class="inline-formula">CO<sub>2</sub></span> sensor network was deployed across the city of Zurich (Switzerland), known as ZiCOS-M. The network was operational between July 2022 and July 2024 and consisted of 26 monitoring sites, 21 of which were located in or around the city of Zurich, with 5 sites outside the urban area. Daily calibrations using two reference gas cylinders and corrections of the sensors' spectroscopic response to water vapour were performed to reach a high level of measurement accuracy. The hourly mean root mean squared error (RMSE) was 0.98 <span class="inline-formula">ppm</span> (range of 0.46 and 1.5 <span class="inline-formula">ppm</span>) and the mean bias ranged between <span class="inline-formula">−</span>0.72 and 0.66 <span class="inline-formula">ppm</span> when undergoing parallel measurements with a high-precision reference gas analyser for a period of 2 weeks or more. <span class="inline-formula">CO<sub>2</sub></span> concentrations (technically, dry-air mole fractions) were highly variable with site means in Zurich ranging from 434 to 460 <span class="inline-formula">ppm</span>, and Zurich's mean urban <span class="inline-formula">CO<sub>2</sub></span> dome was 15.4 <span class="inline-formula">ppm</span> above the regional background. Some of the highest <span class="inline-formula">CO<sub>2</sub></span> levels were found at two sites exposed to strong plant respiration in a very confined nocturnal boundary layer. High-<span class="inline-formula">CO<sub>2</sub></span> episodes were detected outside Zurich's urban area, demonstrating that processes acting on a variety of scales drove <span class="inline-formula">CO<sub>2</sub></span> levels. The ZiCOS-M network offered significant insights at a cost an order of magnitude lower compared to reference instruments, and the observations generated by ZiCOS-M will be used in additional ICOS Cities activities to conduct <span class="inline-formula">CO<sub>2</sub></span> emission inventory validation with inversion modelling systems.</p>
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spelling doaj-art-2004a71f5b2f44f9b168b4756af5b6e02025-08-20T03:16:24ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242025-03-01252781280610.5194/acp-25-2781-2025The ZiCOS-M CO<sub>2</sub> sensor network: measurement performance and CO<sub>2</sub> variability across ZurichS. K. Grange0S. K. Grange1S. K. Grange2P. Rubli3A. Fischer4D. Brunner5C. Hueglin6L. Emmenegger7Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Air Pollution / Environmental Technology, Überlandstrasse 129, 8600 Dübendorf, SwitzerlandWolfson Atmospheric Chemistry Laboratories, University of York, York, YO10 5DD, United Kingdomcurrently at: School of Earth and Atmospheric Sciences, Queensland University of Technology, Gardens Point, Brisbane, Queensland, 4000, AustraliaEmpa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Air Pollution / Environmental Technology, Überlandstrasse 129, 8600 Dübendorf, SwitzerlandEmpa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Air Pollution / Environmental Technology, Überlandstrasse 129, 8600 Dübendorf, SwitzerlandEmpa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Air Pollution / Environmental Technology, Überlandstrasse 129, 8600 Dübendorf, SwitzerlandEmpa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Air Pollution / Environmental Technology, Überlandstrasse 129, 8600 Dübendorf, SwitzerlandEmpa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Air Pollution / Environmental Technology, Überlandstrasse 129, 8600 Dübendorf, Switzerland<p>As a component of the ICOS Cities project, a “mid-cost” NDIR (nondispersive infrared) <span class="inline-formula">CO<sub>2</sub></span> sensor network was deployed across the city of Zurich (Switzerland), known as ZiCOS-M. The network was operational between July 2022 and July 2024 and consisted of 26 monitoring sites, 21 of which were located in or around the city of Zurich, with 5 sites outside the urban area. Daily calibrations using two reference gas cylinders and corrections of the sensors' spectroscopic response to water vapour were performed to reach a high level of measurement accuracy. The hourly mean root mean squared error (RMSE) was 0.98 <span class="inline-formula">ppm</span> (range of 0.46 and 1.5 <span class="inline-formula">ppm</span>) and the mean bias ranged between <span class="inline-formula">−</span>0.72 and 0.66 <span class="inline-formula">ppm</span> when undergoing parallel measurements with a high-precision reference gas analyser for a period of 2 weeks or more. <span class="inline-formula">CO<sub>2</sub></span> concentrations (technically, dry-air mole fractions) were highly variable with site means in Zurich ranging from 434 to 460 <span class="inline-formula">ppm</span>, and Zurich's mean urban <span class="inline-formula">CO<sub>2</sub></span> dome was 15.4 <span class="inline-formula">ppm</span> above the regional background. Some of the highest <span class="inline-formula">CO<sub>2</sub></span> levels were found at two sites exposed to strong plant respiration in a very confined nocturnal boundary layer. High-<span class="inline-formula">CO<sub>2</sub></span> episodes were detected outside Zurich's urban area, demonstrating that processes acting on a variety of scales drove <span class="inline-formula">CO<sub>2</sub></span> levels. The ZiCOS-M network offered significant insights at a cost an order of magnitude lower compared to reference instruments, and the observations generated by ZiCOS-M will be used in additional ICOS Cities activities to conduct <span class="inline-formula">CO<sub>2</sub></span> emission inventory validation with inversion modelling systems.</p>https://acp.copernicus.org/articles/25/2781/2025/acp-25-2781-2025.pdf
spellingShingle S. K. Grange
S. K. Grange
S. K. Grange
P. Rubli
A. Fischer
D. Brunner
C. Hueglin
L. Emmenegger
The ZiCOS-M CO<sub>2</sub> sensor network: measurement performance and CO<sub>2</sub> variability across Zurich
Atmospheric Chemistry and Physics
title The ZiCOS-M CO<sub>2</sub> sensor network: measurement performance and CO<sub>2</sub> variability across Zurich
title_full The ZiCOS-M CO<sub>2</sub> sensor network: measurement performance and CO<sub>2</sub> variability across Zurich
title_fullStr The ZiCOS-M CO<sub>2</sub> sensor network: measurement performance and CO<sub>2</sub> variability across Zurich
title_full_unstemmed The ZiCOS-M CO<sub>2</sub> sensor network: measurement performance and CO<sub>2</sub> variability across Zurich
title_short The ZiCOS-M CO<sub>2</sub> sensor network: measurement performance and CO<sub>2</sub> variability across Zurich
title_sort zicos m co sub 2 sub sensor network measurement performance and co sub 2 sub variability across zurich
url https://acp.copernicus.org/articles/25/2781/2025/acp-25-2781-2025.pdf
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