Aircraft-based measurements of the carbon footprint of Indianapolis
The quantification of greenhouse gas emissions requires high spatial resolution and high precision measurements. Here measurements of carbon dioxide (CO2) and methane (CH4) conducted using Purdue University’s Airborne Laboratory for Atmospheric Research (ALAR), aimed at the quantification of the “footprints” for these greenhouse gases for Indianapolis, Indiana, are described. A cavity ring-down spectrometer measured atmospheric concentrations, and flask samples were obtained at various points for comparison. Coupled with pressure, temperature, and model-derived horizontal winds, these measurements allow for flux estimation. Long horizontal transects were flown perpendicular to the wind downwind of the city. Emissions were calculated using the wind speed and the difference between the concentration in the plume and the background concentration. A kriging method was applied to interpolate the measured values to a vertical plane. Results show the urban plume is clearly distinguishable in the downwind concentrations. Additionally, there is large variability in the measured day-to-day emissions fluxes as well as in the relative CH4 and CO2 fluxes.^
Paul B. Shepson, Purdue University.
Atmospheric Chemistry|Atmospheric Sciences