Ground-based remote sensing of carbon dioxide and methane in the Arctic using Fourier-transform infrared spectrometry

Abstract

The abundances of the atmospheric greenhouse gases carbon dioxide and methane are monitored across the globe by a network of ground-based solar absorption Fourier-transform infrared spectrometers, the Total Carbon Column Observing Network (TCCON). In this dissertation, the existing measurement time series of both gases, taken at the TCCON site in Ny-A lesund, Spitsbergen, has been augmented in two ways: extension to measurements during the polar night and the usage of middle-infrared spectra. In addition to the near-infrared TCCON measurements, spectra in the middle-infrared are routinely taken in Ny-A lesund. The newly obtained data from these spectra are compared to the standard TCCON retrieval. Additionally, in the high Arctic, measurements of solar absorption spectra are not possible in winter, because the Sun is permanently below the horizon. A new detector for measurements in the near-infrared is introduced and spectra were recorded between 2012 and 2016 to retrieve the column averaged dry-air mole fractions of CO2 and CH4. The lunar measurements were validated and compared to results from various reanalysis model simulations as well as in-situ measurements.