An Evaluation Of Calibration Techniques For In Situ Carbon Dioxide Measurements Using A Programmable Portable Trace-Gas Measuring System

  • Sites: US-NR1, US-NR2
  • Publication Type: JOUR
  • Authors: Burns, S. P.; Delany, A. C.; Sun, J.; Stephens, B. B.; Oncley, S. P.; Maclean, G. D.; Semmer, S. R.; Schröter, J.; Ruppert, J.

  • The construction and deployment of a portable trace-gas measurement system (TGaMS) is described. The air-collection system (dubbed HYDRA) collects air samples from 18 different locations and was connected to either one or two LI-COR LI-7000 gas analyzers to measure CO2. An in situ “field calibration” method, that uses four calibration gases with an uncertainty on the order of ±0.1 μmol mol−1 relative to the WMO CO2 mole fraction scale, revealed CO2 output from the LI-7000 had a slightly nonlinear relationship relative to the CO2 concentration of the calibration gases. The sensitivity of the field-calibrated CO2 to different forms of the field-calibration equation is investigated. To evaluate TGaMS performance, CO2 from collocated inlets, portable gas cylinders, and nearby independent CO2 instruments are compared. Results are as follows: 1) CO2 measurements from HYDRA multiple inlets are feasible with a reproducibility of ±0.4 μmol mol−1 (based on the standard deviation of the CO2 difference between collocated inlets when HYDRA was operating with two LI-7000s); 2) CO2 differences among the various field-calibration equations were on the order of ±0.3 μmol mol−1; and 3) comparison of midday hourly CO2 measurements at 30 m AGL between TGaMS and an independent high-accuracy CO2 measurement system (within 300 m of TGaMS) had a median difference and standard deviation of 0.04 ± 0.81 μmol mol−1 over two months.


  • Journal: Journal Of Atmospheric And Oceanic Technology
  • Funding Agency: —
  • Citation Information:
  • Volume: 26
  • No: 2
  • Pages: 291-316
  • Publication Year: 2009/02
  • DOI: 10.1175/2008JTECHA1080.1
  • https://doi.org/10.1175/2008JTECHA1080.1