Continuous measurements of greenhouse gases and atmospheric oxygen at the Namib Desert Atmospheric Observatory

• Published in: Atmospheric measurement techniques Vol. 8; no. 6; pp. 2233 - 2250
• Main Authors: Morgan, E. J, Lavrič, J. V, 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, Thompson, R. L, Schmidt, S, Manning, A. C, Heimann, M
• Format: Journal Article
• Language: English
• Published: Katlenburg-Lindau Copernicus GmbH 01-06-2015; Copernicus Publications
• Subjects: Air pollution; Atmosphere; Atmospheric carbon dioxide; Atmospheric methane; Atmospheric oxygen; Atmospheric particulates; Atmospherics; Basic oxides; Biogeochemistry; Calibration; Carbon; Carbon cycle; Carbon dioxide; Carbon dioxide measurements; Carbon monoxide; Coastal environments; Coasts; Corrections; Cylinders; Daily temperatures; Desert environments; Deserts; Diurnal; Drying; Dust storms; Fog; Fuel cells; Fuel technology; Gases; Greenhouse effect; Greenhouse gases; Handling; Holes; Instruments; Measurement; Meteorology; Methane; Nitrous oxide; Nitrous oxides; Observatories; Oxides; Oxygen; Precipitation; Pressure regulators; Respiration; Sand; Stainless steel; Temperature; Temperature control; Temperature requirements; Temperature variability; Time series; Namib Desert; United States > US; Germany; Africa; Namibia, Namib Desert; PSW, Namibia
• ISSN: 1867-8548; 1867-1381; 1867-8548; 1867-1381
• DOI: 10.5194/amt-8-2233-2015

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 reference cylinder.