Articles | Volume 9, issue 6
Research article
17 Jun 2016
Research article |  | 17 Jun 2016

Measurements of greenhouse gases at Beromünster tall-tower station in Switzerland

Tesfaye Ayalneh Berhanu, Ece Satar, Rudiger Schanda, Peter Nyfeler, Hanspeter Moret, Dominik Brunner, Brian Oney, and Markus Leuenberger

Abstract. In order to constrain the regional flux of greenhouse gases, an automated measurement system was built on an old radio tower at Beromünster, Switzerland. The measurement system has been running since November 2012 as part of the Swiss greenhouse gases monitoring network (CarboCount-CH), which is composed of four measurement sites across the country. The Beromünster tall tower has five sampling lines with inlets at 12.5, 44.6, 71.5, 131.6, and 212.5 m above ground level, and it is equipped with a Picarro cavity ring-down spectrometer (CRDS) analyzer (G-2401), which continuously measures CO, CO2, CH4, and H2O. Sensors for detection of wind speed and direction, air temperature, barometric pressure, and humidity have also been installed at each height level. We have observed a non-negligible temperature effect in the calibration measurements, which was found to be dependent on the type of cylinder (steel or aluminum) as well as trace gas species (strongest for CO). From a target gas of known mixing ratio that has been measured once a day, we have calculated a long-term reproducibility of 2.79 ppb, 0.05 ppm, and 0.29 ppb for CO, CO2, and CH4, respectively, over 19 months of measurements. The values obtained for CO2 and CH4 are compliant with the WMO recommendations, while the value calculated for CO is higher than the recommendation. Since the installation of an air-conditioning system recently at the measurement cabin, we have acquired better temperature stability of the measurement system, but no significant improvement was observed in the measurement precision inferred from the target gas measurements. Therefore, it seems that the observed higher variation in CO measurements is associated with the instrumental noise, compatible with the precision provided by the manufacturer.

Short summary
In this manuscript, we have presented Co, CO2 and CH4 measurement data from an old radio tower tower (217.5 m) at Beromunster, Switzerland. From about 2 years of continuous CO, CO2 and CH4 measurement at five different heights, we have determined a long-term reproducibility of 2.79 ppb, 0.05 ppm and 0.29 ppb for CO, CO2 and CH4, respectively, compliant with the GAW requirements. We have also observed seasonal and diurnal variation of these species.