Sources of variability in atmospheric CO2 in an urban environment

Open Access
- Author:
- Mcgowan, Laura Elizabeth
- Graduate Program:
- Meteorology
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- June 18, 2013
- Committee Members:
- Kenneth James Davis, Thesis Advisor/Co-Advisor
Aijun Deng, Thesis Advisor/Co-Advisor
William Henry Brune, Thesis Advisor/Co-Advisor - Keywords:
- co2
meteorology - Abstract:
- Anthropogenic emissions of carbon dioxide (CO2) have contributed the most to the increased radiative forcing of all changes in greenhouse gases since the preindustrial era. Understanding its sources and sinks is critical to the mitigation of future climate change. Sources and sinks of CO2 are not as well known on city scales. It is important to improve the uncertainty in urban-scale CO2 budgets since regional/local scales are where polices are most likely to be implemented. The months of February and July 2011 were simulated over Indianapolis, Indiana with the atmospheric transport model Weather Research and Forecasting Advanced Research Model (WRF-ARW) version 3.2 to a) quantify the impact of anthropogenic city emissions on regional CO2 atmospheric mole fractions under a variety of meteorological conditions and seasons, b) determine how much biogenic fluxes of CO2 within the city and all fluxes outside of the city contribute to the CO2 mole fraction in an urban atmosphere, and c) explore the importance of the resolution of fossil fuel emission products on simulated CO2 mole fractions. Anthropogenic emissions were simulated with the Vulcan and Hestia data products. It was found that local anthropogenic emissions within the city lead to detectable but modest enhancements in the atmospheric CO2 mole fraction over Indianapolis. There were large day-to-day variations in the buildup of CO2 in urban boundary layer which were explained in part by the variability in atmospheric boundary layer (ABL) depth and wind speed. A sound approach to generalizing these results to other urban areas was established using wind speed and ABL depth along with surface emissions. The detection of city emissions was substantially easier in the winter compared to the summer; biogenic fluxes had large contributions to the cross-city CO2 mole fractions in the summer. Lastly, lower resolution anthropogenic emissions from Vulcan were found to underestimate the day-to-day variability in cross-city CO2 values compared to the results from the higher resolution Hestia product.