Preprints
https://doi.org/10.5194/egusphere-2024-2939
https://doi.org/10.5194/egusphere-2024-2939
16 Oct 2024
 | 16 Oct 2024
Status: this preprint is open for discussion and under review for Atmospheric Measurement Techniques (AMT).

The Turbulent Enhancement Ratio as a novel Approach for Characterizing Local Emission Sources in Complex Environments

Christian Lamprecht, Martin Graus, Marcus Striednig, Michael Stichaner, Werner Jud, Andreas Held, and Thomas Karl

Abstract. In this study, we introduce the Turbulent Enhancement Ratio (TER) method as a new approach for characterizing local emission sources in complex urban environments, with a focus on the city of Innsbruck, Austria. The idea behind the approach is to take advantage of highly time resolved trace gas observations, that allow identifying turbulent air motions, from which a turbulent enhancement ratio can be constructed. We use a comprehensive measurement setup at the Innsbruck Atmospheric Observatory utilizing advanced instruments to test the approach. Our dataset, spanning from mid-2018 to early 2022, includes periods affected by the COVID-19 pandemic, allowing us to assess the impact of reduced traffic and changes in domestic fuel use on NOx/CO2 emission ratios. We test the approach by comparing with direct eddy covariance flux measurements of these tracers. The results show a statistically significant linear relationship between TER and the flux ratio of NOx over CO2, with regression slopes ranging between 0.96 to 1.1. Weekday TER values are generally higher due to increased traffic, while weekend values are lower, reflecting reduced commuter activity. Seasonal analysis shows that winter TER is influenced significantly by domestic heating, while in summer, traffic is the predominant source of NOx and CO2 emissions within the measurement footprint. The diurnal cycle of TER also highlights the role of valley wind systems in modulating local emissions through changes in footprint, with valley-up winds bringing higher traffic-related emissions to the site during the day. Our findings demonstrate that TER is a robust predictor for emission ratios in urban settings, offering insights into the dynamics of local emissions. The method's ability to capture turbulent fluctuations provides a more nuanced understanding of source contributions, particularly in environments with complex and mixed emission sources.

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Christian Lamprecht, Martin Graus, Marcus Striednig, Michael Stichaner, Werner Jud, Andreas Held, and Thomas Karl

Status: open (until 07 Dec 2024)

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Christian Lamprecht, Martin Graus, Marcus Striednig, Michael Stichaner, Werner Jud, Andreas Held, and Thomas Karl
Christian Lamprecht, Martin Graus, Marcus Striednig, Michael Stichaner, Werner Jud, Andreas Held, and Thomas Karl

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Short summary
Air pollution management requires accurate determination of emissions and emission ratios of air pollutants. In this paper, we explore a new way to resolve excess mixing ratios in turbulent plumes, which allows aggregation of unbiased ensemble averages of air pollutant ratios that can be compared with emission models. The approach is tested in an urban environment and used to resolve emission patterns of nitrogen oxides and carbon dioxide.