The Indianapolis Flux Experiment (INFLUX): A test-bed for developing urban greenhouse gas emission measurements

Abstract

The objective of the Indianapolis Flux Experiment (INFLUX) is to develop, evaluate and improve methods for measuring greenhouse gas (GHG) emissions from cities. INFLUX's scientific objectives are to quantify CO 2 and CH 4 emission rates at 1 km 2 resolution with a 10% or better accuracy and precision, to determine whole-city emissions with similar skill, and to achieve high (weekly or finer) temporal resolution at both spatial resolutions. The experiment employs atmospheric GHG measurements from both towers and aircraft, atmospheric transport observations and models, and activity-based inventory products to quantify urban GHG emissions. Multiple, independent methods for estimating urban emissions are a central facet of our experimental design. INFLUX was initiated in 2010 and measurements and analyses are ongoing. To date we have quantified urban atmospheric GHG enhancements using aircraft and towers with measurements collected over multiple years, and have estimated whole-city CO 2 and CH 4 emissions using aircraft and tower GHG measurements, and inventory methods. Significant differences exist across methods; these differences have not yet been resolved; research to reduce uncertainties and reconcile these differences is underway. Sectorally-and spatially-resolved flux estimates, and detection of changes of fluxes over time, are also active research topics. Major challenges include developing methods for distinguishing anthropogenic from biogenic CO 2 fluxes, improving our ability to interpret atmospheric GHG measurements close to urban GHG sources and across a broader range of atmospheric stability conditions, and quantifying uncertainties in inventory data products. INFLUX data and tools are intended to serve as an open resource and test bed for future investigations. Well-documented, public archival of data and methods is under development in support of this objective.

Assessing a low-cost methane sensor quantification system for use in complex rural and urban environments

“…For example, the National Oceanic and Atmospheric Administration (NOAA) has maintained a global monitoring network for methane for upwards of 30 years to study long-term atmospheric trends, seasonal cycles, and its global distribution (NOAA, 2017). Monitoring networks can also be built on smaller scales to study methane fluxes at the regional or city level; the Megacities Carbon Project is currently undertaking this work in Southern California, as is the INFLUX project in Indianapolis (Wong et al, 2015;Davis et al, 2017). Remote sensing provides a global picture and, given the spatial coverage, these data can highlight hotspots at the regional scale (Kort et al, 2014).…”

Top‐Down Estimates of NOx and CO Emissions From Washington, D.C.‐Baltimore During the WINTER Campaign

“…Airborne observations of urban emissions from D.C.-Balt have been previously discussed (Anderson et al, 2014;Brent et al, 2015;Castellanos et al, 2011;Hains et al, 2008;He et al, 2013He et al, , 2014He et al, , 2016Marufu et al, 2004;Taubman et al, 2006). Observations conducted during WINTER in 2015 are compared with measurements conducted by the UMD aircraft the following February (2016) in D. C.-Balt, andin Indianapolis, IN in November to December 2014 (Heimburger et al, 2017), as part of the Indianapolis Flux Experiment (Davis et al, 2017).…”

Reconciling the differences between a bottom-up and inverse-estimated FFCO2 emissions estimate in a large US urban area

“…The Indianapolis Flux Experiment (INFLUX) experiment emerged from research aimed at quantifying space-and time-explicit fossil fuel carbon dioxide emissions (Hestia) in the city of Indianapolis (Gurney et al, 2012;Davis et al, 2017). The INFLUX effort now includes the original bottomup quantification system, aircraft-based in situ measurement of CO 2 , CH 4 , and CO fluxes, and dense, tower-based continuous measurement of mole fraction for CO 2 , CH 4 , and CO (Cambaliza et al, 2014(Cambaliza et al, , 2015Heimburger et al, 2017;Miles et al, 2016) and flask measurements of CO 2 , CH 4 , CO, 14 CO 2 and a host of other species (Turnbull et al, 2012;Turnbull et al, 2015).…”