Search Results (4)

The COllaborative Carbon Column Observing Network has become a reliable source of high-quality ground-based remote sensing network data that provide column-averaged dry-air mole fractions of carbon dioxide (XCO₂), methane (XCH₄), and carbon monoxide (XCO). The fiducial reference measurements of these gases from the COCCON complement the TCCON and NDACC-IRWG data. This study shows the application of COCCON data for the validation of existing greenhouse gas satellite products. This study includes the validation of XCH₄ and XCO products from the European Copernicus Sentinel-5 Precursor (S5P) mission, XCO₂ products from the American Orbiting Carbon Observatory-2 (OCO-2) mission, and XCO₂ and XCH₄ products from the Japanese Greenhouse gases Observing SATellite (GOSAT). A total of 27 datasets contributed to this study; some of these were collected in the framework of campaign activities and covered only a short time period. In addition, several permanent stations provided long-term observations. The random uncertainties in the validation results, specifically for S5P with a lot of coincidences pairs, are found to be similar to the comparison with the TCCON. The comparison results of OCO-2 land nadir and land glint observation modes to the COCCON on a global scale, despite limited coincidences, are very promising. The stations can, therefore, expand on the coverage of the already existing ground-based reference remote sensing sites from the TCCON and the NDACC network. The COCCON data can be used for future satellite and model validation studies and carbon cycle studies. Full article

Carbon monoxide, XCO, and methane, XCH₄, column-averaged dry-air mole fractions (DMFs), observed by the TROPOspheric Monitoring Instrument (TROPOMI) on board Sentinel-5P (S-5P), are validated against those obtained from a Bruker ground-based low-resolution Fourier transform spectrometer, EM27/SUN, operating in the framework and according to requirements of the Collaborative Carbon Column Observing Network (COCCON), in Thessaloniki, Greece, on a mid-latitude urban site. The current operational S5P/TROPOMI observations show very good agreement with the respective FTIR measurements and capture both their seasonal variability and pollution episodes. XCO reported the highest concentrations during the fire episodes in summer 2021, when its daily mean value reached a maximum of 0.134 ± 0.015 ppm. XCH₄ shows a slight annual increase of 0.02 ppm, with the highest concentrations during early 2022 (approximately 1.92 ppm). The satellite CH₄ and CO products have been recently reprocessed with updated CH₄, CO and H₂O cross-sections, among other improvements, bringing noticeable changes in the pre-existing biases of S5P products against the FTIR ground-based data. We report that, for this mid-latitude station, mean biases and standard deviations fall well within mission requirements for XCH₄ and XCO (−0.01 ± 0.6% and 0.62 ± 4.2% for XCH₄ and XCO, respectively), underlying the significance of satellite measurements as a valuable supplement to ground-based data for the purpose of greenhouse gas monitoring. The results presented in this work for the Thessaloniki FTIR instrument are in strong agreement with FTIR locations in the middle latitudes. Full article

The issue of atmospheric pollution in urban centers has become a growing concern in recent years. The increasing levels of greenhouse gases in the atmosphere are a major contributor to atmospheric pollution, and it is imperative to monitor these gases. This study presents the measurements of column-averaged dry-air mole fractions of carbon dioxide (XCO₂) and carbon monoxide (XCO) in Thessaloniki, Greece. The measurements were taken in Thessaloniki using the Bruker EM27/SUN instrument, which was developed by Bruker and KIT and has been part of the Collaborative Carbon Column Observing Network (COCCON) since 2018. COCCON is a global network of stations around the globe and serves as an important supplement to the high-resolution Bruker IFS125 spectrometer used in the Total Carbon Column Observing Network (TCCON), and it provides an increased density of column-averaged greenhouse gas observations. In this work, a four-year analysis of column-averaged dry-air mole fractions of XCO₂ and XCO is presented, focusing on diurnal and seasonal cycles as well as on the comparison between them. The hourly time series show the expected seasonal cycle of XCO₂ with a spring maximum and late summer minimum due to photosynthesis activity, while XCO₂ presents a daily maximum of 419.987 ± 2.286 ppm and a daily minimum of 405.001 ± 3.067 ppm. The seasonal co-variability between XCO₂ and XCO reveals an interesting correlation—especially during winter (${\mathrm{R}}^2=0.841$ for 2022) and spring (${\mathrm{R}}^2=0.437 \mathrm{for} 2022$) period, when anthropogenic emission sources occur. Full article

In this work, column-averaged dry-air mole fractions of carbon dioxide (XCO₂), methane (XCH₄) and carbon monoxide (XCO) are presented for the first time at a mid-latitude urban station, Thessaloniki, Greece, using the Bruker EM27/SUN ground-based low-resolution Fourier Transform spectrometer operated according to the requirements of the Collaborative Carbon Column Observing Network (COCCON). Two years of measurements are presented and examined for seasonal variability. The observed XCO₂ levels show the expected seasonal cycle (spring maximum, late summer minimum) with a peak-to-peak amplitude of 12 ppm, with maximum values reported for winter 2021 exceeding 416 ppm. The XCH₄ values are shown to increase in the second half of the year, with autumn showing the highest mean value of 1.878 ± 0.01 ppm. The XCO levels, following anthropogenic sources, show high winter and low summer values, exhibiting a rise again in August and September with a maximum value of 114 ± 3 ppb and a minimum in summer 2020 of 76 ± 3 ppb. Additionally, methane and carbon monoxide products obtained from the TROPOspheric Monitoring Instrument (TROPOMI), Sentinel-5P space borne sensor, are compared with the ground-based measurements. We report a good agreement between products. The relative mean bias for methane and carbon monoxide are −0.073 ± 0.647% and 3.064 ± 5.566%, respectively. Furthermore, a 15-day running average is subtracted from the original daily mean values to provide ΔXCO₂, ΔXCO and ΔXCH₄ residuals, so as to identify local sources at a synoptic scale. ΔXCO and ΔXCO₂ show the best correlation in the winter (R² = 0.898, slope = 0.007) season due to anthropogenic emissions in this period of the year (combustion of fossil fuels or industrial activities), while in summer no correlation is found. ΔXCO and ΔXCH₄ variations are similar through both years of measurements and have a very good correlation in all seasons including winter (R² = 0.804, slope = 1.209). The investigation of the X-gases comparison is of primary importance in order to identify local sources and quantify the impact of these trace gases to the deregulation of earth-climate system balance. Full article