Continuous measurements of greenhouse gases and atmospheric oxygen at the Namib Desert Atmospheric Observatory
Author:
Morgan E. J., Lavrič J. V.ORCID, Seifert T., Chicoine T., Day A., Gomez J., Logan R., Sack J., Shuuya T., Uushona E. G., Vincent K., Schultz U., Brunke E.-G., Labuschagne C.ORCID, Thompson R. L.ORCID, Schmidt S., Manning A. C.ORCID, Heimann M.ORCID
Abstract
Abstract. A new coastal background site has been established for observations of greenhouse gases (GHGs) in the central Namib Desert at Gobabeb, Namibia. The location of the site was chosen to provide observations for a data-poor region in the global sampling network for GHGs. Semi-automated, continuous measurements of carbon dioxide, methane, nitrous oxide, carbon monoxide, atmospheric oxygen, and basic meteorology are made at a height of 21 m a.g.l., 50 km from the coast at the northern border of the Namib Sand Sea. Atmospheric oxygen is measured with a differential fuel cell analyzer (DFCA). Carbon dioxide and methane are measured with an early-model cavity ring-down spectrometer (CRDS); nitrous oxide and carbon monoxide are measured with an off-axis integrated cavity output spectrometer (OA-ICOS). Instrument-specific water corrections are employed for both the CRDS and OA-ICOS instruments in lieu of drying. The performance and measurement uncertainties are discussed in detail. As the station is located in a remote desert environment, there are some particular challenges, namely fine dust, high diurnal temperature variability, and minimal infrastructure. The gas handling system and calibration scheme were tailored to best fit the conditions of the site. The CRDS and DFCA provide data of acceptable quality when base requirements for operation are met, specifically adequate temperature control in the laboratory and regular supply of electricity. In the case of the OA-ICOS instrument, performance is significantly improved through the implementation of a drift correction through frequent measurements of a working tank.
Publisher
Copernicus GmbH
Reference58 articles.
1. Andrews, A. E., Kofler, J. D., Trudeau, M. E., Williams, J. C., Neff, D. H., Masarie, K. A., Chao, D. Y., Kitzis, D. R., Novelli, P. C., Zhao, C. L., Dlugokencky, E. J., Lang, P. M., Crotwell, M. J., Fischer, M. L., Parker, M. J., Lee, J. T., Baumann, D. D., Desai, A. R., Stanier, C. O., De Wekker, S. F. J., Wolfe, D. E., Munger, J. W., and Tans, P. P.: CO2, CO, and CH4 measurements from tall towers in the NOAA Earth System Research Laboratory's Global Greenhouse Gas Reference Network: instrumentation, uncertainty analysis, and recommendations for future high-accuracy greenhouse gas monitoring efforts, Atmos. Meas. Tech., 7, 647–687, https://doi.org/10.5194/amt-7-647-2014, 2014. 2. Arévalo-Martínez, D. L., Beyer, M., Krumbholz, M., Piller, I., Kock, A., Steinhoff, T., Körtzinger, A., and Bange, H. W.: A new method for continuous measurements of oceanic and atmospheric N2O, CO and CO2: performance of off-axis integrated cavity output spectroscopy (OA-ICOS) coupled to non-dispersive infrared detection (NDIR), Ocean Sci., 9, 1071–1087, https://doi.org/10.5194/os-9-1071-2013, 2013. 3. Baer, D., Paul, J., Gupta, M., and O'Keefe, A.: Sensitive absorption measurements in the near-infrared region using off-axis integrated-cavity-output spectroscopy, Appl. Phys. B, 75, 261–265, 2002. 4. Battle, M., Mikaloff Fletcher, S., Bender, M., Keeling, R., Manning, A., Gruber, N., Tans, P., Hendricks, M., Ho, D., Simonds, C., Mika, R., and Paplawsky, B.: Atmospheric potential oxygen: new observations and their implications for some atmospheric and oceanic models, Global Biogeochem. Cy., 20, GB1010, https://doi.org/10.1029/2005GB002534, 2006. 5. Bender, M., Tans, P., Ellis, J., Orchardo, J., and Habfast, K.: A high precision isotope ratio mass spectrometry method for measuring the O2 / N2 ratio of air, Geochim. Cosmochim. Ac., 58, 4751–4758, 1994.
|
|