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Abstract

This cumulative thesis assesses several ways of improving greenhouse gas flux estimates and consists of four main parts. Firstly, within the framework of a measurement campaign, CO2, CH4 and N2O measurements of different instruments and between different measurement networks were compared and differences of 0.14 ppm (CO2), 0.04 ppb (CH4) and 0.37 ppb (N2O) were found, respectively. The main result is that N2O differences could partly be explained by a difference between the WMO N2O X2006a reference scale and the SIO-1998 scale. Secondly, 18O(CO2) retrievals were implemented in a Fourier Transform Infrared spectrometer, allowing for continuous CO2 gross fluxes estimates. The measurements are compatible to mass spectrometer measurements and have a precision of about 0.3h, which suffices to detect δ18O(CO2) variations in Heidelberg. Thirdly, in a model study, possible tracers for estimating continuous anthropogenic CO2 were assessed. δ13C(CO2) and CO are well suited for this, but only in urban areas and if the isotopic signature and the emission ratio CO/CO2 of the mean anthropogenic CO2 source are known. Finally, a method to estimate the hourly δ13C(CO2) source signature accurately (median: 0.2 permil) and precisely (interquartile range: 1.2 permil) is proposed. Applying the method to Heidelberg data, a seasonal cycle is observed. It allows estimation of the isotopic signature of one source, but only if the contributions from other sources are small.