Abstract
Abstract. Over the last few decades, in situ measurements of atmospheric N2O mole fractions have been performed using gas chromatographs (GCs) equipped with electron capture detectors. This technique, however, becomes very challenging when trying to detect the small variations of N2O as the detectors are highly nonlinear and the GCs at remote stations require a considerable amount of maintenance by qualified technicians to maintain good short-term and long-term repeatability. With new robust optical spectrometers now available for N2O measurements, we aim to identify a robust and stable analyzer that can be integrated into atmospheric monitoring networks, such as the Integrated Carbon Observation System (ICOS). In this study, we present the most complete comparison of N2O analyzers, with seven analyzers that were developed and commercialized by five different companies. Each instrument was characterized during a time period of approximately 8 weeks. The test protocols included the characterization of the short-term and long-term repeatability, drift, temperature dependence, linearity and sensitivity to water vapor. During the test period, ambient air measurements were compared under field conditions at the Gif-sur-Yvette station. All of the analyzers showed a standard deviation better than 0.1 ppb for the 10 min averages. Some analyzers would benefit from improvements in temperature stability to reduce the instrument drift, which could then help in reducing the frequency of calibrations. For most instruments, the water vapor correction algorithms applied by companies are not sufficient for high-precision atmospheric measurements, which results in the need to dry the ambient air prior to analysis.
Highlights
Nitrous oxide (N2O) is a greenhouse gas with an atmospheric lifetime of 131 years and a global warming potential that is approximately 300 times that of CO2 at a 100-year time horizon (Prather et al, 2012)
High-precision atmospheric N2O measurements in flask measurement networks and at in situ stations are traditionally measured by gas chromatographs (GCs) using an electron capture detector
We present the first assessment of the performance of seven N2O analyzers and compare these techniques to routine instruments, including a GC analyzer (Lopez et al, 2012) that is used at LSCE (Laboratoire des Sciences du Climat et de l’Environnement) for ambient air measurements since 2001 and a Fourier transform infrared (FTIR) that has been running since 2012
Summary
Nitrous oxide (N2O) is a greenhouse gas with an atmospheric lifetime of 131 years and a global warming potential that is approximately 300 times that of CO2 at a 100-year time horizon (Prather et al, 2012). At the 17th WMO/IAEA meeting, 10–13 June 2013 in Beijing, an expert group on CO2 and other greenhouse gases from the World Meteorological Organization Global Atmosphere Watch (WMO/GAW) recommended an N2O inter-laboratory comparability goal of ±0.1 ppb (http://www.wmo.int/pages/prog/ arep/gaw/documents/Final_GAW_213_web.pdf) This ambitious goal has not yet been reached, as shown recently by Bergamaschi et al (2015), who found biases between in situ gas chromatography (GC) measurements and flask sampling at different European stations of up to 0.7 ppb. High-precision atmospheric N2O measurements in flask measurement networks and at in situ stations are traditionally measured by GC using an electron capture detector Methods incorporating this technique have achieved a typical short-term continuous measurement repeatability (CMR) of 0.1 to 0.3 ppb (Lopez et al, 2012; Nevison et al, 2011; Popa et al, 2010; Schmidt et al, 2001). While the tests have been carried out in the frame of ICOS, the results are valid for all groups and networks doing highprecision atmospheric N2O measurements
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