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Measuring Methane using a ground-based FTIR spectrometer in the Arctic

In 2014, the globally averaged concentration of methane (CH4) reached 1824 ppb, which is a 150% increase from its preindustrial concentration of 722 ppb. CH4 has a global warming potential of 20 times that of carbon dioxide over a 100 year time period and the atmospheric concentration continues to increase. About 40% of CH4 is emitted into the atmosphere from natural sources and the reaming 60% is from human activities.  As climate change melts the Arctic, increased exposure of permafrost and wetland formation could result in increased emissions of CH4 from the Arctic. Therefore it is important that we monitor CH4 emissions in the Arctic to help determine regional sources of Arctic CH4.

The Total Carbon Column Observing Network (TCCON) is a ground-based network of Fourier transform infrared (FTIR) spectrometers that measure precise and accurate columns of CH4 and other greenhouse gases. Solar spectra are recorded using a Bruker 125 HR spectrometer and then processed by a nonlinear least square retrieval algorithm (GGG) in order to determine total columns of CH4. The network is continuously updating methodology in order to improve the accuracy and precision of measurements.  In this presentation I will focus on the need to improve the calculation of CH4 absorption coefficients and the impact it has on TCCON CH4 retrievals.