Continuous atmospheric CO<sub>2</sub>, CH<sub>4</sub> and CO measurements at the OPE station in France from 2011 to 2018

Abstract

Located in the North East of France, the Observatoire Pérenne de l'Environnement (OPE) station was built during the Integrated Carbon Observation System (ICOS) Demonstration Experiment to monitor the atmospheric concentration of greenhouse gases. Its continental rural background setting allows to fill the gaps between oceanic or mountain background stations and urban stations within the ICOS network. Continuous measurements of several greenhouse gases using high 10 precision spectrometers started in 2011 on a tall tower with three sampling inlets at 10m, 50m and 120m above the ground.The measurements quality are regularly assessed using several complementary approaches based on reference high pressure cylinders, traveling instruments audit and sets of travelling cylinders (so-called cucumber intercomparison). Thanks to the quality assurance strategy recommended by ICOS, the measurements precision are within the WMO compatibility goals for carbon dioxide (CO2), methane (CH4) and carbon monoxide (CO). The mixing ratios time series from 2011 to end of 2018 15 allow analyses of trends and diurnal and seasonal cycles. The CO2 and CH4 annual growth rates are respectively 2.4 ppm/year and 8.8 ppb/year for the 120m above ground measurements over the investigated period. No significant trend has however been recorded for the CO mixing ratios. The afternoon mean residuals of these three compounds are significantly stronger during the cold period when inter-species correlations are high, compared to the warm period. The residuals variabilities show a close link with the air masses back-trajectories. 20

CO2 variability in the Mexico City region from in situ measurements at an urban and a background site

“…For a continental city, however, mountain stations at nearby locations may be a better option. Under the adequate meteorological conditions, these sites capture a free-troposphere, regional background signal better suited to interpret patterns of regional exchange (Zhang et al, 2013;Turnbull et al, 2014;Conil et al, 2019). However, city sources and sinks may still influence the background sites (Zellweger et al, 2009;Zhang et al, 2013;Yuan et al, 2019), thus a screening procedure is needed to assure the regional background estimation is free from the signal of the adjacent urban environment.…”