Assessment of uncertainties of an aircraft-based mass balance approach for quantifying urban greenhouse gas emissions

Abstract

Urban environments are the primary contributors to global anthropogenic carbon emissions. Because much of the growth in CO 2 emissions will originate 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, are described. The relatively level terrain of Indianapolis facilitated the application of mean wind fields in the mass balance approach. We investigate the uncertainties in our aircraft-based mass balance approach by (1) assessing the sensitivity of the measured flux to important measurement and analysis parameters including wind speed, background CO 2 and CH 4 , boundary layer depth, and interpolation technique, and (2) determining the flux at two or more downwind distances from a point or area source (with relatively large source strengths such as solid waste facilities and a power generating station) in rapid succession, assuming that the emission flux is constant. When we quantify the precision in the approach by comparing the estimated emis-sions derived from measurements at two or more downwind distances from an area or point source, we find that the minimum and maximum repeatability were 12 and 52 %, with an average of 31 %. 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 through the measurement period, and increasing the number of downwind horizontal transect measurements at multiple altitudes within the boundary layer.

Constraining sector-specific CO<sub>2</sub> and CH<sub>4</sub> emissions in the US

“…New innovations in atmospheric monitoring and instrumentation may reduce some of these uncertainties. Cambaliza et al (2014), for example, explain that lidar instruments can measure atmospheric mixing height, and lidar deployment could therefore improve certain aspects of atmospheric modeling, particularly at local and regional scales. In addition, several studies develop high-resolution meteorological simulations, in part to better resolve atmospheric GHG transport in urban environments (e.g., McKain et al, 2012McKain et al, , 2015Nehrkorn et al, 2013).…”

Methane and carbon dioxide fluxes and their regional scalability for the European Arctic wetlands during the MAMM project in summer 2012

“…The change in PBL height, z, over the time period t can be estimated using Eq. (4) (Stull, 1988;Cambaliza et al, 2014):…”

Joint inverse estimation of fossil fuel and biogenic CO2 fluxes in an urban environment: An observing system simulation experiment to assess the impact of multiple uncertainties

“…The Indianapolis Flux Experiment (INFLUX, http://sites.psu.edu/influx/) was proposed to develop, test and improve methods to estimate anthropogenic GHG emissions from cities, using Indianapolis as a test bed . This project uses aircraft (Cambaliza et al, 2014;Heimburger et al, 2017) and a high-density surface tower network Richardson et al, 2017) combined with high-resolution atmospheric modeling Sarmiento et al, 2017) to infer CO 2 ff emissions at 1 km spatial resolution (Lauvaux et al, 2016). Figure 1 shows the distribution of instrumented towers and daytime average surface CO 2 fluxes during the first 10 days of September 2013.…”