Atmospheric Measurement Techniques Discussions www.atmos-meas-tech-discuss.net 1867-8610 3 2 2010 10.5194/amtd-3-1399-2010 http://www.atmos-meas-tech-discuss.net/3/1399/2010/ http://www.atmos-meas-tech-discuss.net/3/1399/2010/amtd-3-1399-2010.html http://www.atmos-meas-tech-discuss.net/3/1399/2010/amtd-3-1399-2010.pdf 1399 1437 2010-03-31 Continuous low-maintenance CO₂/CH₄/H₂O measurements at the Zotino Tall Tower Observatory (ZOTTO) in Central Siberia J. Winderlich jan.winderlich@bgc-jena.mpg.de H. Chen A. Höfer C. Gerbig T. Seifert O. Kolle C. Kaiser J. V. Lavrič M. Heimann Max Planck Institute for Biogeochemistry, Hans-Knöll-Straße 10, 07745 Jena, Germany Laboratoire des Sciences du Climat et de l'Environnement, Orme des Merisiers, 91191 Gif-sur-Yvette, France The Zotino Tall Tower Observatory in Central Siberia (ZOTTO, 60°48' N, 89°21' E) is an excellent location to monitor the continental carbon cycle. Since April 2009, a fully automated low maintenance measurement system based on a cavity ring-down spectroscopy (CRDS) analyzer is installed at the site to measure continuously carbon dioxide (CO₂) and methane (CH₄) from six heights up to 301 m a.g.l. Buffer volumes in each air line remove short term CO₂ and CH₄ mixing ratio fluctuations associated with turbulence, and allow continuous, near-concurrent measurements from all six tower levels. Instead of drying the air sample, the simultaneously measured water vapor is used to correct the dilution and pressure-broadening effects for the accurate determination of dry air CO₂ and CH₄ mixing ratios. The stability of the water vapor correction was demonstrated by repeated laboratory and field tests. The effect of molecular adsorption in the wet air lines was shown to be negligible. The low consumption of four calibration tanks that need recalibration only on decadal timescale further reduces maintenance. 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