The CarboCount CH sites: characterization of a dense greenhouse gas observation network

Abstract

Abstract. We describe a new rural network of four densely placed ( < 100 km apart), continuous atmospheric carbon (CO 2 , CH 4 , and CO) measurement sites in north-central Switzerland and analyze its suitability for regional-scale (∼ 100-500 km) carbon flux studies. We characterize each site for the period from March 2013 to February 2014 by analyzing surrounding land cover, observed local meteorology, and sensitivity to surface fluxes, as simulated with the Lagrangian particle dispersion model FLEXPART-COSMO (FLEXible PARTicle dispersion model-Consortium for Small-Scale Modeling).The Beromünster measurements are made on a tall tower (212 m) located on a gentle hill. At Beromünster, regional CO 2 signals (measurement minus background) vary diurnally from −4 to +4 ppmv, on average, and are simulated to come from nearly the entire Swiss Plateau, where 50 % of surface influence is simulated to be within 130-260 km distance. The Früebüel site measurements are made 4 m above ground on the flank of a gently sloping mountain. Nearby (< 50 km) pasture and forest fluxes exert the most simulated surface influence, except during convective summertime days when the site is mainly influenced by the eastern Swiss Plateau, which results in summertime regional CO 2 signals varying diurnally from −5 to +12 ppmv and elevated summer daytime CH 4 signals (+30 ppbv above other sites). The Gimmiz site measurements are made on a small tower (32 m) in flat terrain. Here, strong summertime regional signals (−5 to +60 ppmv CO 2 ) stem from large, nearby (< 50 km) crop and anthropogenic fluxes of the Seeland region, except during warm or windy days when simulated surface influence is of regional scale (< 250 km). The Lägern-Hochwacht measurements are made on a small tower (32 m) on top of the steep Lägern crest, where simulated surface influence is typically of regional scale (130-300 km) causing summertime regional signals to vary from −5 to +8 ppmv CO 2 . Here, considerable anthropogenic influence from the nearby industrialized region near Zurich causes the average wintertime regional CO 2 signals to be 5 ppmv above the regional signals simultaneously measured at the Früebüel site.We find that the suitability of the data sets from our current observation network for regional carbon budgeting studies largely depends on the ability of the high-resolution (2 km) atmospheric transport model to correctly capture the temporal dynamics of the stratification of the lower atmosphere at the different sites. The current version of the atmospheric transport model captures these dynamics well, but it clearly reaches its limits at the sites in steep topography and at the sites that generally remain in the surface layer. Trace gas transport and inverse modeling studies will be necessary to determine the impact of these limitations on our ability to dePublished by Copernicus Publications on behalf of the European Geosciences Union. 11148B. Oney et al.: Greenhouse gas observation network characterization rive reliable regional-scale carbon flux estimate...

The CarbonTracker Data Assimilation Shell (CTDAS) v1.0: implementation and global carbon balance 2001–2015

“…A second regional application focuses on Switzerland, and is developed at ETH Zürich. CT-DAS is combined with the new tracer transport module of the regional numerical weather prediction model COSMO, and is used to estimate carbon fluxes in Switzerland, making use of CO 2 observations from four new measurement sites around Switzerland (Liu, 2017;Oney et al, 2015). The resulting CO 2 flux estimates match well with the bottom-up estimates.…”

Estimation of the fossil fuel component in atmospheric CO&lt;sub&gt;2&lt;/sub&gt; based on radiocarbon measurements at the Beromünster tall tower, Switzerland

“…While about 70 % of this contribution is due to Swiss NPPs, the remaining contribution is of foreign origin. About 75 % of the contribution from the Swiss NPPs is due to Mühleberg, which is located west of Beromünster and hence frequently upstream of the site, due to the prevailing westerly winds (Oney et al, 2015). Note that each data point represents a mean value of the triplicate samples collected consecutively with a standard error of 2 ‰ among triplicates.…”

“…The influence of 14 C emissions from nearby NPPs and correction strategies are also discussed. A detailed description of the Beromünster tall tower measurement system as well as a characterization of the site with respect to local meteorological conditions, seasonal and diurnal variations of greenhouse gases, and regional representativeness can be obtained from previous publications (Oney et al, 2015;Berhanu et al, 2016;Satar et al, 2016). In brief, the tower is located near the southern border of the Swiss Plateau, the comparatively flat part of Switzerland between the Alps in the south and the Jura Mountains in the northwest (47 • 11 23 N, 8 • 10 32 E, 797 m a.s.l.…”

Continuous CO&lt;sub&gt;2&lt;/sub&gt;/CH&lt;sub&gt;4&lt;/sub&gt;/CO measurements (2012–2014) at Beromünster tall tower station in Switzerland

“…Local wind conditions will likely correlate with the measurements to some extent, but they are not a reliable indicator of air mass origin and surface influence and thus are not very well suited to classify the data. According to Oney et al (2015), winds are strongly channeled between the Alps and the Jura mountains along a south-west to north-east axis and wind speeds have a diurnal cycle with a minimum in the morning and a maximum around mid-night (at the highest elevation). The latter is likely due to the top of the tower being usually located above the nocturnal boundary layer.…”