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.

Urban emissions of water vapor in winter

“…Airborne mass balance experiments were performed with the Purdue and the UMD aircraft to quantify citywide GHG emissions from Indianapolis and D.C.‐Balt [ Trainer et al ., ; Kalthoff et al ., ; Mays et al ., ; Karion et al ., , ; Gioli et al ., ; O'Shea et al ., ; Pétron et al ., ; Cambaliza et al ., , ; Lavoie et al ., ; Heimburger et al ., ]. Alternative airborne methods for estimating urban fluxes of energy, greenhouse gases, and other anthropogenic pollutants have been reported [ Font et al ., ; Karl et al ., ; Trousdell et al ., ; Vaughan et al ., ].…”

What is the role for carbon cycle science in the proposed EPA power plant rule?

“…Given recent research in the carbon science community, the reliability with which state's will be able to quantify their baseline emission rate and demonstrate compliance in the target years, is a legitimate question. However, there is ongoing work in the carbon science community that may offer independent, scientifically-rigorous means to assess and ultimately better-quantify power plant CO 2 emissions and emission rates (Mays et al 2009;Gurney et al 2012;Kort et al 2012;McKain et al 2012;Cambaliza et al 2013;Bréon et al 2014;Lindenmaier et al 2014;Turnbull et al 2015). Research could be aimed at better understanding the current monitoring systems to isolate accuracy/ precision problems and improve better uncertainty quantification.…”

“…A CMS will integrate and synthesize a wide variety of observational data on carbon stocks and flows (ground-based, aircraft and space-based) within modeling systems. An outgrowth of the CMS aimed at scales closer to what might be needed for supporting the EPA proposed rule are a series of research efforts in the urban domain, where scientific observational and modeling systems are attempting to quantify fluxes at finer space/time scales and attribute fluxes to sectoral activity or even individual emitting entities (Mays et al 2009;Gurney et al 2012;Kort et al 2012;McKain et al 2012;Cambaliza et al 2013;Bréon et al 2014;Turnbull et al 2015).…”

Tower-based greenhouse gas measurement network design—The National Institute of Standards and Technology North East Corridor Testbed

“…Urban carbon studies have increased in recent years, with diverse motivations ranging from urban ecology research to testing methods for independently verifying GHG emissions inventory reports and estimates. Examples of these are Salt Lake City (McKain et al, 2012), Houston (Brioude et al, 2012), Paris (Bréon et al, 2015), Los Angeles (Duren and Miller, 2012) and Indianapolis (INFLUX; Cambaliza et al, 2014; Turnbull et al, 2015; Lauvaux et al, 2016). Different measurement approaches have been used to independently measure GHG emissions.…”

“…The first two testbeds are the INFLUX experiment (Cambaliza et al, 2014; Lauvaux et al, 2016) and the LA Megacities project (Duren and Miller, 2012). As with the other testbeds, the NEC project will use atmospheric inversion methods to quantify sources of GHG emissions in the urban areas.…”