Abstract

<p>Urban areas are recognised as a significant source of greenhouse gas emissions (GHG), such as carbon dioxide (CO<sub>2</sub>) and methane (CH<sub>4</sub>). The total amount of urban GHG emissions, especially for CH<sub>4</sub>, however, is not well quantified. Here we report on airborne in situ measurements using a Picarro G1301-m analyser aboard the DLR Cessna Grand Caravan to study GHG emissions downwind of the German capital city Berlin. In total, five aircraft-based mass balance experiments were conducted in July 2018 within the Urban Climate Under Change [UC]<sup>2</sup> project. The detection and isolation of the Berlin plume was often challenging because of comparatively small GHG signals above variable atmospheric background concentrations. However, on July 20<sup>th</sup> enhancements of up to 4 ppm CO<sub>2</sub> and 21 ppb CH<sub>4</sub> were observed over a horizontal extent of roughly 45 to 65 km downwind of Berlin. These enhanced mixing ratios are clearly distinguishable from the background and can partly be assigned to city emissions. The estimated CO<sub>2</sub> emission flux of 1.39 ± 0.75 t s<sup>-1 </sup>is in agreement with current inventories, while the CH<sub>4</sub> emission flux of 5.20 ± 1.61 kg s<sup>-1</sup> is almost two times larger than the highest reported value in the inventories. We localized the source area with HYSPLIT trajectory calculations and the high resolution numerical model MECO(n) (down to ~1 km), and investigated the contribution from sewage-treatment plants and waste deposition to CH<sub>4</sub>, which are treated differently by the emission inventories. Our work highlights the importance of a) strong CH<sub>4</sub> sources in the surroundings of Berlin and b) a detailed knowledge of GHG inflow mixing ratios to suitably estimate emission rates.</p>

Highlights

  • Atmospheric mixing ratios of well-known greenhouse gases (GHGs), such as carbon dioxide (CO2) and methane (CH4), have increased by a factor of 1.4 and 2.5, respectively, compared to pre-industrial times (Hartmann et al, 2013)

  • 4 Conclusion An improved understanding and quantification of the GHG budget is needed for the development of efficient mitigation strategies and for the prediction of future climate impacts

  • With our study we contribute to the sparse knowledge of GHG emissions from European cities by studying the urban CO2 and CH4 distribution downwind of the German capital Berlin

Read more

Summary

Introduction

Atmospheric mixing ratios of well-known greenhouse gases (GHGs), such as carbon dioxide (CO2) and methane (CH4), have increased by a factor of 1.4 and 2.5, respectively, compared to pre-industrial times (Hartmann et al, 2013). These gases contribute substantially to global warming due to the increased absorption of outgoing infrared radiation. The Paris Agreement (UNFCCC, 2015) aims to keep the global temperature rise below 2°C compared to pre-industrial levels.

Objectives
Methods
Results
Discussion
Conclusion

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.