Xing, Z., Barchyn, T. E., Vollrath, C., Gao, M., & Hugenholtz, C. (2023). Satellite-Derived Estimate City-Level Methane Emission Flux from Calgary, Alberta, Canada.
Xing, Z., Barchyn, T. E., Vollrath, C., Gao, M., & Hugenholtz, C. (2023). Satellite-Derived Estimate City-Level Methane Emission Flux from Calgary, Alberta, Canada.
Xing, Z., Barchyn, T. E., Vollrath, C., Gao, M., & Hugenholtz, C. (2023). Satellite-Derived Estimate City-Level Methane Emission Flux from Calgary, Alberta, Canada.
Xing, Z., Barchyn, T. E., Vollrath, C., Gao, M., & Hugenholtz, C. (2023). Satellite-Derived Estimate City-Level Methane Emission Flux from Calgary, Alberta, Canada.
Abstract
Cities are important sources of anthropogenic methane emissions. Municipal governments can play a role in reducing those emissions to support climate change mitigation, but they need information on the rate of emissions to context mitigation actions and track progress. Here, we examine the application of satellite data from the TROPOspheric Monitoring Instrument (TROPOMI) to estimate city-level methane emissions rates in a case study of the City of Calgary, Alberta, Canada. While satellites are touted as a global methane monitoring system, we found limited observational coverage over Calgary that precluded the reliability of measurement-based models to track the annual emissions. In this work, we integrated valid observations over three years (2020-22) and used mass balance modeling to derive a long-term averaged emission estimate. The column-averaged dry-air mole fraction (XCH4) enhancement over Calgary was small, 4.7 ppb, but within the city boundary, we identified local hot spots in the vicinity of known sources (wastewater treatment facility and landfills). The city-scale emissions estimate from mass balance was 215.4 ± 132.8 t/d CH4. This estimate is approximately four- and six-times larger than estimates from Canada's gridded national inventory report of anthropogenic CH4 emissions and the Emissions Database for Global Atmospheric Research (EDGAR v8.0), respectively. Valid observations are more common in warmer months and occur during a narrow daily overpass timeslot over Calgary – these effects may bias the emissions estimate. Overall, the findings from this case study highlight the challenge of deriving routine (sub-annual to annual) satellite-based estimates of city-scale methane emissions in similar geographic settings and suggest that more granular emissions inventories are needed to improve methane reporting.
Keywords
methane; TROPOMI; mass balance; emission estimate; city-level
Subject
Environmental and Earth Sciences, Remote Sensing
Copyright:
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
