Greenhouse Gas Emissions of Indianapolis using a High-Density Surface Tower Network and an Atmospheric Inversion

Friday, 19 December 2014: 9:00 AM
Natasha L Miles1, Thomas Lauvaux2, Kenneth J Davis2, Scott Richardson2, Aijun Deng2, Daniel P Sarmiento2, Kai Wu2, Colm Sweeney3, Anna Karion4, Robert Michael Hardesty3, Alan Brewer4, Jocelyn C Turnbull5, Laura T Iraci6, Patrick W Hillyard7, James Robert Podolske6, Kevin R Gurney8, Risa Patarasuk8, Maria Obiminda L Cambaliza9, Paul B Shepson10 and James R Whetstone11, (1)Penn State Univ, University Park, PA, United States, (2)Pennsylvania State University Main Campus, University Park, PA, United States, (3)Cooperative Institute for Research in Environmental Sciences, Boulder, CO, United States, (4)NOAA, Earth System Research Laboratory, Boulder, CO, United States, (5)GNS Science / Rafter Radiocarbon, Lower Hutt, New Zealand, (6)NASA Ames Research Center, Moffett Field, CA, United States, (7)Bay Area Environmental Research Institute Moffett Field, Moffett Field, CA, United States, (8)Arizona State University, Tempe, AZ, United States, (9)Purdue University, West Lafayette, IN, United States, (10)Purdue Univ, West Lafayette, IN, United States, (11)National Institute of Standards and Technology Gaithersburg, Gaithersburg, MD, United States
The Indianapolis Flux Experiment (INFLUX) was designed to develop and evaluate methods of detection and attribution of greenhouse gas fluxes from urban environments. Determination of greenhouse gas fluxes and uncertainty bounds is essential for the evaluation of the effectiveness of mitigation strategies. Indianapolis is intended to serve as a test bed for these methods; the results will inform efforts at measuring emissions from urban centers worldwide, including megacities. The generally accepted method for determining urban greenhouse gas emissions is inventories, which are compiled from records of land use and human activity. Atmospheric methods, in which towers are instrumented with sensors to measure greenhouse gas mole fractions and these data are used in an inversion model, have the potential to provide independent determination of emissions.

The current INFLUX observation network includes twelve in-situ tower-based, continuous measurements of CO2. A subset of five towers additionally measure CH4, and a different subset measure CO. The subset measuring CO also include weekly flask samples of a wide variety of trace gases including 14CO2. Here we discuss the observed urban spatial and temporal patterns in greenhouse gas mole fraction in Indianapolis, with the critical result being the detectability of city emissions with this high-density network. We also present the first atmospheric inversion results for both CO2 and CH4, compare these results to inventories, and discuss the effects of critical assumptions in the inversion framework. The construction of unbiased atmospheric modeling systems and well-defined prior errors remains an important step in atmospheric emissions monitoring over urban areas. In order to minimize transport model errors, we developed a WRF-Chem FDDA modeling system ingesting surface and profile measurements of horizontal mean wind, temperature, and moisture. We demonstrate the impact of the meteorological data assimilation system on the inverse flux estimates.