Calibration of TCCON column-averaged CO sub(2): the first aircraft campaign over European TCCON sites

• Published in: Atmospheric chemistry and physics 2011-11, Vol.11 (21), p.10765-10777
• Main Authors: Messerschmidt, J, Geibel, M C, Blumenstock, T, Chen, H, Deutscher, N M, Engel, A, Feist, D G, Gerbig, C, Gisi, M, Hase, F
• Format: Article
• Language: English
• ISSN: 1680-7316; 1680-7324

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 CO sub(2), CH sub(4), N sub(2)O, CO and O sub(2) are measured. CO sub(2) is constrained with a precision better than 0.25% (1- sigma ). 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 CO sub(2) 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 CO sub(2) measurements of total column concentrations provide a suitable database for the calibration and validation of nadir-viewing satellites.