SMuK 2021 – scientific programme
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UP: Fachverband Umweltphysik
UP 6: Poster Session
UP 6.5: Poster
Friday, September 3, 2021, 16:30–18:30, P
Direct measurement of methane radiative forcing in Ny-Ålesund — •Lukas Heizmann, Mathias Palm, Justus Notholt, and Matthias Buschmann — Universität Bremen, Bremen, Germany
Methane is an important greenhouse gas with significant increase in concentration between pre-industrial times and today, corresponding to an associated estimated increase in radiative forcing of +0.48 W/m2 compared to +2.83 W/m2 for all well-mixed greenhouse gases (IPCC 2013). However direct measurement of the radiative forcing attributed to methane proved to be difficult. Feldmann et al. (2018) presented a a first study using ground-based measurement at a single location (ARM Southern Great Plains atmospheric observatory). We investigate the feasibility of such measurements in the Arctic using a calibrated FTIR emission spectrometer in Ny-Ålesund, Spitsbergen. Due to nearby water vapor absorption lines, methane radiative forcing is mediated by the thermodynamic state of the atmosphere. We thus retrieve water vapor and methane profiles simultaneously to produce counterfactual spectra in which the only difference from the true atmosphere consists in the methane mixing ratio. By differencing the true with the counterfactual spectra and integrating over the entire spectral range we obtain a measurement of the radiative forcing of methane.