Remote sensing of greenhouse gases with FTIR spectroscopy and estimate of their emissions ; Τηλεπισκόπηση θερμοκηπικών αερίων με φασματοσκοπία FTIR και εκτίμηση των εκπομπών τους

A portable direct solar viewing Bruker EM27/SUN FTIR (Fourier Transform InfraRed) spectrometer has been installed in the urban city of Thessaloniki, Greece since January 2019, in the frame of the COllaborative Carbon Column Observing Network (COCCON), performing measurements of total column-averaged dry air mole fractions of greenhouse gases such as carbon dioxide (XCO2), methane (XCH4) and water vapor (XH2O) or carbon monoxide (XCO). Concerning the annual variability, the amplitude of the seasonal cycle in Thessaloniki’s CO2 concentrations follows the pattern of a typical mid-northern hemisphere COCCON site with a discernible seasonal variability and an interannual increase of about 2-3 ppm. XCO2 shows maximum concentrations with 424.94 ± 0.573 ppm, while a minimum is observed at 2019/07/22 with a value of 404.82 ± 0.602 ppm. XCO does not always show a pronounced annual cycle. XCO shows higher values during winter due to anthropogenic emissions (such as incomplete combustion of fossil fuels, heating during the cold period and industrial activities in the northern and north-western part of the city) and minimum during late spring and summer when hydroxyl radical (OH) concentrations are at its peak. Higher concentrations of XCO are found during summer 2021 and 2023 capturing extreme high concentrations (over 0.22 ppm) as a consequence of prolonged fire episodes. OH is a common sink of carbon monoxide (XCO) and methane (XCH4). XCH4 shows lower values at the beginning of the year up until spring, is rising during the summer, with the maximum appearing in autumn. The relative peak-to-peak change between years of observations is around 3.2% and an annual increase of over 11 ppb is observed in the region of Thessaloniki. The increase in XCH4 concentrations during summer can be attributed to both temperature rise or fire episodes and emissions from the rice cultivation period. Additionally, methane and carbon monoxide products obtained from the TROPOspheric Monitoring Instrument (TROPOMI), Sentinel-5P space borne ...