%0 Generic
%A Schmitt, Tobias Dieter
%C Heidelberg
%D 2024
%F heidok:34470
%R 10.11588/heidok.00034470
%T An Open-Path Observatory for Greenhouse Gases based on High Resolution Fourier Transform Spectroscopy
%U https://archiv.ub.uni-heidelberg.de/volltextserver/34470/
%X Measuring the atmospheric concentrations of Greenhouse Gases (GHGs) like carbon dioxide (CO2) and methane (CH4) is crucial to improve our knowledge of their sources and sinks.  This is essential to understand our climate system, but also to quantify, verify, and attribute anthropogenic emissions of GHGs.  For the latter, urban areas are particularly important, but pose unique challenges due to often highly structured emission patterns.  Here, I present the design, setup, and implementation of an open-path observatory, which measures averaged GHGs concentrations along a 1.55 km long path and evaluate its performance.  I compare these measurements to in-situ measurements to evaluate their respective representativeness on a kilometer-scale grid.    Averaging over five minutes, the open-path observatory achieves precisions of 1.4 ppm (0.32%) and of 8.3 ppb (0.40%) for CO2 and CH4 dry air mole fractions, respectively.  Overall, the open-path and in-situ measurements agree well, but I also identify conditions, such as south-easterly winds, where discrepancies of up to 20 ppm occur in CO2.  Such differences can seriously impact emission estimates obtained from pairing measurements with kilometer-scale atmospheric transport models.  I demonstrate that the observatory can provide a sound measurement basis for further investigations into the representativeness issue and offers unique opportunities to validate and improve spectroscopic databases.  Both can contribute to general improvements to atmospheric remote sensing of GHGs.