Articles | Volume 13, issue 9
Research article
03 May 2016
Research article |  | 03 May 2016

Continuous CO2/CH4/CO measurements (2012–2014) at Beromünster tall tower station in Switzerland

Ece Satar, Tesfaye A. Berhanu, Dominik Brunner, Stephan Henne, and Markus Leuenberger

Abstract. The understanding of the continental carbon budget is essential to predict future climate change. In order to quantify CO2 and CH4 fluxes at the regional scale, a measurement system was installed at the former radio tower in Beromünster as part of the Swiss greenhouse gas monitoring network (CarboCount CH). We have been measuring the mixing ratios of CO2, CH4 and CO on this tower with sample inlets at 12.5, 44.6, 71.5, 131.6 and 212.5 m above ground level using a cavity ring down spectroscopy (CRDS) analyzer. The first 2-year (December 2012–December 2014) continuous atmospheric record was analyzed for seasonal and diurnal variations and inter-species correlations. In addition, storage fluxes were calculated from the hourly profiles along the tower. The atmospheric growth rates from 2013 to 2014 determined from this 2-year data set were 1.78 ppm yr−1, 9.66 ppb yr−1 and −1.27 ppb yr−1 for CO2, CH4 and CO, respectively. After detrending, clear seasonal cycles were detected for CO2 and CO, whereas CH4 showed a stable baseline suggesting a net balance between sources and sinks over the course of the year. CO and CO2 were strongly correlated (r2 > 0.75) in winter (DJF), but almost uncorrelated in summer. In winter, anthropogenic emissions dominate the biospheric CO2 fluxes and the variations in mixing ratios are large due to reduced vertical mixing. The diurnal variations of all species showed distinct cycles in spring and summer, with the lowest sampling level showing the most pronounced diurnal amplitudes. The storage flux estimates exhibited reasonable diurnal shapes for CO2, but underestimated the strength of the surface sinks during daytime. This seems plausible, keeping in mind that we were only able to calculate the storage fluxes along the profile of the tower but not the flux into or out of this profile, since no Eddy covariance flux measurements were taken at the top of the tower.

Short summary
Beromünster tall tower is the flagship of the densely placed Swiss greenhouse gas observation network (CarboCount CH). In this research article we report the first 2 years of the continuous greenhouse gas measurements using cavity ring down spectroscopy analyzer from this tall tower. We have adopted a purely observation based, multi-species and multi-level approach to characterize the site with respect to sources and sinks of natural and anthropogenic origin at diurnal to annual timescales.
Final-revised paper