Ground based FTIR and MAX-DOAS observations of greenhouse and trace gas emissions in the Rhine valley (Germany), St. Petersburg and Yekaterinburg (Russia)

The anthropogenic emissions of greenhouse gases and air pollutants in the atmosphere have increased and worsened since the beginning of the industrial era, resulting in considerable impact on the environment and the atmosphere. Global warming, mainly caused by the anthropogenic emissions of CO$_2$ , is one of the most alarming and discussed consequences that keep the planet under threat of rising Earth temperatures above 1.5°C within the coming two decades (IPCC AR6 WG1, The Physical Science Basis, 2021). Pinning down the anthropogenic emissions of GHGs emission is a pending task that requires enormous political and societal efforts, will, and immediate actions. For several years this topic has been discussed on the transnational level. The negotiations translate into international agreements, the most recent being the Paris agreement in 2016. Therefore, precise and accurate methods for monitoring and quantifying those GHGs in the atmosphere are vital.
Additionally, it is crucial to study the natural sources and sinks of GHGs into the atmosphere to understand climate change better and allow for reliable projections of their future under climate change conditions. ... mehrBoth applications require representative measurements, as achievable by remote sensing techniques. However, measuring relatively minor changes in column-averaged GHG concentrations on top of an extensive accumulated background requires high-accuracy instrumentation and calls for continuous efforts to improve the instrumental and data processing state-of-the-art.

The work presented in this thesis encompasses the crucial topics mentioned before. In the first part, improved calibration procedures for the COllaborative Carbon Column Observing Network (COCCON) are presented. COCCON is an emerging global network of portable EM27/SUN FTIR spectrometers for deriving precise and accurate column-averaged atmospheric abundances of greenhouse gases. The original laboratory open-path lamp measurements for deriving the spectrometer's instrumental line shape (ILS) from water vapour lines have been refined and extended to the second detector channel incorporated in the EM27/SUN spectrometer for the detection of carbon monoxide (CO). The refinements encompass improved spectroscopic line lists for the relevant water lines and a revision of the laboratory pressure measurements used to analyze the spectra. Finally, a revision and extension of the COCCON network instrument-to-instrument calibration factors for XCO$_{2}$, XCO, and XCH$_{4}$ is presented, incorporating 47 new spectrometers (of 83 in total by now).

In the second part, the results of the city emission campaign carried out in St. Petersburg as a case study in Eastern Europe, aiming at empirically quantifying the CO$_2$, CO, and CH$_4$ city emissions, are presented and compared with available inventories sources. This campaign utilized two portable EM27/SUN FTIR instruments operated at daily variable locations based on St. Petersburg's forecasted wind direction. After the mobile campaign, one instrument remained in a continuous mode of operation in Peterhof (a suburb of St. Petersburg), and the other instrument was moved to Yekaterinburg in 2019 and 2020. The collected measurements, during approximately one year, were analyzed, and the results are compared to all available satellite products (TROPOMI, OCO-2, GOSAT, and MUSICA IASI), showing generally good agreement with COCCON observations. As a final result, the gradients between both cities are analyzed and compared with Copernicus Atmosphere Monitoring Service (CAMS) model data. Satellite and ground-based observations at high latitudes are much sparser than at low or mid-latitudes, which makes direct coincident comparisons between remote-sensing observations more difficult, but at the same time, assigns these measurements a great scientific value.

The final chapter presents the results of the remote sensing measurements used for the study case region in the Rhine valley area. This area was selected due to the variety of the emission sources located in the surrounding: industry, urban, power, forest, and agricultural sectors. TCCON and MAX-DOAS observations were performed at KIT Campus North from 2019 to 2021 in order to investigate the ratios of column-averaged abundance ($\Delta$XCO/$\Delta$XCO$_2$ and $\Delta$NO$_{2,\text{VCD}}$/$\Delta$XCO$_2$) for separating the anthropogenic emissions of CO$_2$; the results were compared to the in-situ, and TNO high-resolution inventory data results. The $\Delta proxy / \Delta$ffCO$_2$ ratios found are in the range of the TNO emissions ratios corresponding to the industry sector, which is supported by the predominant wind direction, advecting air from an industrial area located in the South-West of the Campus. Several significant transport events have been detected.