NWC REU 2016
May 23 - July 29



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Quantifying the Carbon Footprint on Paris with Remote Sensing Observations

Briana Lynch and Sean Crowell


What is already known:

  • Previous studies have shown that urban areas have a larger amplitude seasonal cycle of carbon dioxide concentrations.
  • The basic interaction between atmospheric dynamics and pollutants in the planetary boundary layer has been studied, but its contribution to urban environments is not well understood.
  • Near surface horizontal lidar instruments quantify carbon dioxide concentrations for the boundary layer more effectively than airborne and space-borne measurements, since the column average is less sensitive to the boundary layer.
  • Disaggregation of natural and anthropogenic sources of CO2 is difficult and relies on existing inventories to interpret measurements.

What this study adds:

  • This study used a new observational technique determine carbon dioxide concentration sources and sinks.
  • This work confirmed that the Greenhouse gas Laser Imaging Tomography Experiment (GreenLITE) made science-quality measurements for six months in an urban environment.
  • A preliminary result shows that nitrogen dioxide is positively correlated with carbon dioxide, while ozone seems to be anti-correlated with carbon dioxide, though the mechanism is still not understood.


Understanding the complex temporally and spatially varying carbon dioxide (CO2) emissions in urbanized areas is crucial to identifying causes of climate change and how they can be addressed. While many studies have been conducted to better quantify urban CO2 (and other pollutant) fluxes, there are still many open questions about the interpretation of these measurements and how emissions scale with population, as well as how to attribute concentrations measured in urban environments to anthropogenic and natural sources and sinks. After deployment for six months (November 2015-April 2016) in Paris, France, data from the Greenhouse gas Laser Imaging Tomography Experiment (GreenLITEā„¢), an observing system that combines laser-based differential absorption spectroscopy measurements with tomographic techniques to create a two dimensional map of CO2 concentrations, was interpreted and analyzed. An evolution equation for CO2 mixing ratio within the Planetary Boundary Layer (PBL) was applied to identify and separate sources and sinks of CO2. Results from this analysis directly verify the impacts that wind speed and direction have on CO2, namely dilution and enhancement. Preliminary analysis characterized the relationships between CO2 and nitrogen dioxide (NO2) and ozone (O3). GreenLITEā„¢) proves to be an accurate measuring tool for CO2, but further interpretation and analysis of data is necessary to estimate the emissions of Paris.

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