|Paper title||Greenhouse gas measurements at Sodankylä, Finland and comparisons with satellite borne observations|
|Form of presentation||Poster|
Greenhouse gas measurements by a Fourier Transform Spectrometer (FTS) were established at Sodankylä (67.4° N, 26.6° E) in early 2009 (Kivi and Heikkinen, 2016). The instrument records high-resolution solar spectra in the near-infrared spectral region. From the spectra we derive column-averaged, dry-air mole fractions of methane (XCH4), carbon dioxide (XCO2) and other gases. The instrument participates in the Total Carbon Column Observing Network (TCCON). Sodankylä is currently the only TCCON site in the Fennoscandia region. Our measurements have contributed to the validation of several satellite-based instruments. The relevant satellite missions include Sentinel-5 Precursor by ESA, the Orbiting Carbon Observatory-2 (OCO-2) by NASA (e.g., Wunch et al., 2017), the Greenhouse Gases Observing Satellite (GOSAT/GOSAT-2) mission by JAXA and the Chinese Carbon Dioxide Observation Satellite Mission (TanSat).
Comparisons with the GOSAT observations of XCH4 and XCO2 taken during years 2009-2020 show good agreement. Mean relative difference in XCH4 has been 0.04 ± 0.02 % and the mean relative difference in XCO2 has been 0.04 ± 0.01 %. We also performed a series of AirCore flights during each season in order to compare FTS retrieval results with the AirCore measurements. AirCore sampling system is directly related to the World Meteorological Organization in situ trace gas measurement scales. Thus the AirCore data can be used to calibrate remote sensing instruments. Our AirCore is a 100 m long coiled sampling tube with a volume of approximately 1400 ml. The sampler is lifted by a meteorological balloon typically up to about 30-35 km altitude and is filled during descent of the instrument from stratosphere down to the Earth's surface. Shortly after landing we have analyzed the sample using a cavity ring-down spectrometer. In addition to the balloon borne AirCore flights we also took measurements of methane and carbon dioxide at a 50 meter tower and by a drone borne AirCore instrument in the vicinity of the FTS site.
Kivi, R. and Heikkinen, P.: Fourier transform spectrometer measurements of column CO2 at Sodankylä, Finland, Geosci. Instrum. Method. Data Syst., 5, 271–279, https://doi.org/10.5194/gi-5-271-2016, 2016.
Wunch, D., et al., Comparisons of the Orbiting Carbon Observatory-2 (OCO-2) XCO2 measurements with TCCON, Atmos. Meas. Tech., 10, 2209-2238, https://doi.org/10.5194/amt-10-2209-2017, 2017.