To monitor the continental carbon cycle, a fullyautomated low maintenance measurement system is installedat the Zotino Tall Tower Observatory in Central Siberia(ZOTTO, 60◦480N, 89◦210E) since April 2009. A cavity ring-down spectroscopy (CRDS) analyzer continuouslymeasures carbon dioxide (CO2) and methane (CH4) fromsix heights up to 301 m a.g.l. Buffer volumes in each airline remove short term CO2 and CH4 mixing ratio fluctuations associated with turbulence, and allow continuous, nearconcurrent measurements from all tower levels. Instead ofdrying the air sample, the simultaneously measured watervapor is used to correct the dilution and pressure-broadeningeffects for the accurate determination of dry air CO2 and CH4mixing ratios. The stability of the water vapor correction wasdemonstrated by repeated laboratory and field tests. The effect of molecular adsorption in the wet air lines was shown tobe negligible. The low consumption of four calibration tanksthat need recalibration only on decadal timescale further reduces maintenance. The measurement precision (accuracy)of 0.04 ppm (0.09 ppm) for CO2 and 0.3 ppb (1.5 ppb) forCH4 is compliant with the WMO recommendations. Thedata collected so far (until April 2010) reveals a seasonal cycle amplitude for CO2 of 30.4 ppm at the 301 m level.