Assessment of Uncertainties of an Aircraft-Based Mass-Balance Approach for Quantifying Urban Greenhouse Gas Emissions

Published

September 2, 2014

Author(s)

Antonio M. Possolo, Daniel V. Samarov, James R. Whetstone

Abstract

Urban environments are the primary contributors to global anthropogenic carbon emissions. Because much of the growth in CO2 emissions will derive from cities, there is a need to develop, assess and improve measurement and modeling strategies for quantifying and monitoring greenhouse gas emissions from large urban centers. In this study the uncertainties in an aircraft-based mass balance approach for quantifying carbon dioxide and methane emissions from an urban environment, focusing on Indianapolis, IN, USA, is described. By flying long transects perpendicular to the prevailing wind direction downwind of the city, enhancements in CO2 and CH4 above the background can be observed at multiple altitudes from the near-surface to the top of the convective boundary layer. The citywide emission is calculated by integrating the incremental flux contributions derived from the product of the enhancements and the observed perpendicular wind speeds. We investigate the uncertainties in our aircraft-based mass balance approach by (1) assessing the sensitivity of the determined flux to various measurement and analysis parameters such as wind speed, background CO2 and CH4, boundary layer depth, and interpolation technique, and (2) determining the flux at two or more downwind distances from a point or area source in rapid succession, assuming that the emission flux is constant. When we quantified the uncertainty in the approach by comparing the estimated emissions derived from measurements at two or more downwind distances from an area or point source, we found that the lower and upper bounds of the uncertainty were 23% and 42%. We suggest that improvements in the experimental design can be achieved by careful determination of the background concentration, monitoring the evolution of the boundary layer, and improving the sampling statistics. Here we discuss methods for improvement, and application to megacities.

Citation

Atmospheric Chemistry and Physics

Pub Type

Journals

Keywords

greenhouse gases, anthropogenic, emissions, mass-balance, uncertainty, carbon dioxide, methane, boundary layer, atmospheric chemistry, flux, interpolation.

Citation

Possolo, A. , Samarov, D. and Whetstone, J. (2014), Assessment of Uncertainties of an Aircraft-Based Mass-Balance Approach for Quantifying Urban Greenhouse Gas Emissions, Atmospheric Chemistry and Physics (Accessed May 10, 2024)