Continuous low-maintenance COsub2/sub/CHsub4/sub/Hsub2/subO measurements at the Zotino Tall Tower Observatory (ZOTTO) in Central Siberia

摘要

To monitor the continental carbon cycle, a fully automated low maintenancemeasurement system is installed at the Zotino Tall Tower Observatory inCentral Siberia (ZOTTO, 60°48' N, 89°21' E) since April 2009. Acavity ring-down spectroscopy (CRDS) analyzer continuously measures carbondioxide (CO₂) and methane (CH₄) from six heights up to 301 m a.g.l. Buffer volumes in each air line remove short term CO₂ andCH₄ mixing ratio fluctuations associated with turbulence, and allowcontinuous, near-concurrent measurements from all tower levels. Instead ofdrying the air sample, the simultaneously measured water vapor is used tocorrect the dilution and pressure-broadening effects for the accuratedetermination of dry air CO₂ and CH₄ mixing ratios. The stabilityof the water vapor correction was demonstrated by repeated laboratory andfield tests. The effect of molecular adsorption in the wet air lines wasshown to be negligible. The low consumption of four calibration tanks thatneed recalibration only on decadal timescale further reduces maintenance.The measurement precision (accuracy) of 0.04 ppm (0.09 ppm) for CO₂ and0.3 ppb (1.5 ppb) for CH₄ is compliant with the WMO recommendations.The data collected so far (until April 2010) reveals a seasonal cycleamplitude for CO₂ of 30.4 ppm at the 301 m level.