A175-0018
Trace gas fluxes derived from open-path FTIR measurements.

Tuesday, 15 December 2020
Poster
Martin Hellmich1, Aldona Wiacek2, Cameron Nicholas Eugene Power3, Morgan Mitchell4 and Ian Ashpole4, (1)Saint Mary's University, Astronomy & Physics, Halifax, NS, Canada, (2)Saint Mary's University, Environmental Science, Astronomy & Physics, Halifax, NS, Canada, (3)Saint Mary's University, Astronomy & Physics, Halifax, Canada, (4)Saint Mary's University, Environmental Science, Halifax, NS, Canada
Abstract:
Open-Path Fourier Transform Infrared Spectroscopy (OP-FTIR) is a well-established technique used to measure boundary layer trace gas concentrations, especially in fenceline monitoring. Recently, the technique has been applied to derivations of trace gas emissions using the flux-gradient approach.

We describe the deployment of a monostatic OP-FTIR spectrometer over a very long atmospheric path (550 m one-way), highlighting some challenges and technical solutions under these measurement conditions, which are representative of newest satellite footprints. We also present details of our retrievals of trace gas concentrations using an iterative non-linear least squares fitting technique, which requires auxiliary data inputs of pressure, temperature, and spectroscopic absorption strength and line broadening parameters.

During the summer of 2018 we made long-path concentration measurements at two different heights and we have access to 2-D anemometer measurements at 2 heights. We will show an approach to calculating an approximation to trace gas fluxes under this scenario. We also made auxiliary in situ measurements of criteria air contaminants and greenhouse gases at both ends of the open-path and we present a study of the representativeness of both measurement geometries, including a comparison to TROPOMI satellite data with a footprint that approaches the long-path length.

In 2020, we anticipate making new measurements (COVID-19 restrictions permitting), including 3-D sonic anemometer data, which allows for a more rigorous application of the flux-gradient method. These methods and results will be discussed, pertaining to greenhouse gases, criteria air contaminants, and VOCs.

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