Abstract
Abstract. The Total Carbon Column Observing Network (TCCON) is a ground-based network of Fourier Transform Spectrometer (FTS) sites around the globe, where the column abundances of CO2, CH4, N2O, CO and O2 are measured. CO2 is constrained with a precision better than 0.25% (1-σ). To achieve a similarly high accuracy, calibration to World Meteorological Organization (WMO) standards is required. This paper introduces the first aircraft calibration campaign of five European TCCON sites and a mobile FTS instrument. A series of WMO standards in-situ profiles were obtained over European TCCON sites via aircraft and compared with retrievals of CO2 column amounts from the TCCON instruments. The results of the campaign show that the FTS measurements are consistently biased 1.1% ± 0.2% low with respect to WMO standards, in agreement with previous TCCON calibration campaigns. The standard a priori profile for the TCCON FTS retrievals is shown to not add a bias. The same calibration factor is generated using aircraft profiles as a priori and with the TCCON standard a priori. With a calibration to WMO standards, the highly precise TCCON CO2 measurements of total column concentrations provide a suitable database for the calibration and validation of nadir-viewing satellites.
Highlights
Carbon dioxide (CO2) is the most abundant anthropogenic greenhouse gas (GHG), and its increase is driving global climate change
The IMECC campaign results a negative bias of 1.1 % ± 0.2 % (2-σ ) of the Fourier Transform Spectrometer (FTS) XCO2 measurements with respect to World Meteorological Organization (WMO) standards
The negative bias is likely due to spectroscopic inaccuracies, as the aircraft profiles were used as a priori profiles
Summary
Carbon dioxide (CO2) is the most abundant anthropogenic greenhouse gas (GHG), and its increase is driving global climate change. The sources and sinks of CO2 are determined by two different approaches: bottom-up and top-down The former estimates the carbon budget by starting with process information at the scale of a few square meters, requiring upscaling to provide information at regional scales. TCCON is a worldwide network of ground-based FTSs that was founded in 2004 It has been largely used as a calibration and validation resource for satellite measurements To provide the link between satellite measurements and the ground-based in-situ network, a sufficiently accurate constraint of trace gas abundances is of critical importance. This paper introduces the first aircraft calibration campaign of European TCCON sites with the same TCCON data retrieval as used by Wunch et al (2010). The results show a European TCCON sites calibration factor for CO2 of 0.989 ± 0.002 (2-σ ) consistent with other TCCON sites (Wunch et al, 2010)
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