Detecting CO2 and CH4 Urban Emissions using Column-Integrated Dry Air mole Fractions, In-Situ Tower Dry Air Mole Fractions, and WRF Modeling

Abstract:

Total column measurements of atmospheric gases are important because of their ability to be performed via satellites that provide global coverage. Here we will present measurements of CO2 and CH4 dry air mole fractions obtained using a Fourier Transform Spectrometer (FTS) as part of the Total Carbon Column Observing Nework (TCCON). These measurements were performed in Indianapolis as part of the Indianapolis Flux Experiment (INFLUX). We will extract urban emission signals using high resolution modeling and in-situ tower measurements of CO2 and CH4 mixing ratios. In addition to quantifying the influence of surface emissions on the column measurements, we will also decompose the atmospheric columns into sub-layers to identify the origin of air masses at various altitudes. We will show that the variability in the origins of air masses increases the complexity of the observed signals in the column, which limits our ability to combine surface and column measurements. This work will also highlight the potential application of using total column measurements to detect local urban signals. We conclude that the deployment of multiple column sensors is required in order to measure the upwind (background) and downwind (urban) conditions. Such work provides a test case for using these methods with satellite measurements such as GOSAT and OCO-2 that provide global coverage.