Progress Towards High-Accuracy, High-Precision, High-Resolution Monitoring of Urban Greenhouse Gas Emissions: Results from INFLUX

Continuous, high-quality monitoring of urban greenhouse gas (GHG) emissions would enable monitoring of emissions mitigation efforts, and an improved understanding of urban metabolism. The Indianapolis Flux Experiment (INFLUX) aims to advance our ability to use atmospheric measurements to quantify urban greenhouse gas (GHG) emissions with high fidelity over extended period of time. The project brings together inventory assessments, tower-based and aircraft-based atmospheric measurements, and atmospheric modeling to provide high-accuracy, high-resolution, continuous monitoring of emissions of GHGs from the city.  We will present a synthesis of progress from INFLUX.  Results to date include a multi-year record of tower and aircraft based measurements of the urban CO2 and CH4 signal, long-term atmospheric modeling of GHG transport, emission estimates for both CO2 and CH4 based on tower and aircraft measurements, and comparison of these estimates to inventories.  Primary sources of uncertainty include atmospheric transport, the mixture of biogenic and multiple anthropogenic fluxes, difficulty determining the atmospheric GHG background, and the nature of the uncertainties in prior flux estimates.  To date, high-fidelity flux estimates can be obtained for the entire urban area during the dormant season.  High spatial resolution flux estimates, source attribution, and sound CO2 flux estimates during the growing season, remain challenging.  We will present ongoing efforts to address these primary sources of uncertainty.