Comparison of gas analyzers for eddy covariance: Effects of analyzer type and spectral corrections on fluxes

Journal Article · Wed Apr 17 00:00:00 EDT 2019 · Agricultural and Forest Meteorology

DOI:https://doi.org/10.1016/j.agrformet.2019.02.010· OSTI ID:1580842

Polonik, P. ^[1]; Chan, W. S. ^[1]; Billesbach, D. P.  ^[2]; Burba, G. ^[3]; Li, J. ^[4]; Nottrott, A. ^[5]; Bogoev, I. ^[6]; Conrad, B. ^[6]; Biraud, S. C.  ^[1]

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1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
2. Univ. of Nebraska, Lincoln, NE (United States)
3. LI-COR Biosciences, Lincoln, NE (United States); Univ. of Nebraska, Lincoln, NE (United States)
4. LI-COR Biosciences, Lincoln, NE (United States)
5. Picarro Inc., Santa Clara, CA (United States)
6. Campbell Scientific, Logan, UT (United States)

The eddy covariance technique (EC) is used at hundreds of field sites worldwide to measure trace gas exchange between the surface and the atmosphere. Data quality and correction methods for EC have been studied empirically and theoretically for many years. The recent development of new gas analyzers has led to an increase in technological options for users. Open-path (no inlet tube) and closed-path (long inlet tube) sensors have been used for a long time, whereas enclosed-path (short inlet tube) sensors are relatively new. In this work, we tested the comparability of fluxes calculated from five different gas analyzers including two open-path (LI-7500 A from LI-COR, IRGASON from Campbell), two enclosed-path (CPEC200 from Campbell, LI-7200 from LI-COR), and one closed-path (2311-f; from Picarro) analyzers, which were all located on a single tower at an irrigated alfalfa field in Davis, CA. To effectively compare sensors with different tube characteristics we used three different spectral correction methods. We found that all sensors, regardless of type, can be used to measure fluxes if appropriate corrections are applied and quality control measures are taken. However, the comparability strongly depended on the gas (CO₂ or H₂O) and the correction method. Average differences were below 4% for CO₂ fluxes using any spectral correction method, but for H₂O average differences were between 4% and 13% for the different methods. The magnitude of corrections also varied strongly, especially for water vapor fluxes. This study does not identify the best sensor, but rather weighs the benefits and difficulties of each sensor and sensor type. Our findings show that enclosed and closed-path gas analyzers that measure water vapor with inlet tubes experience large high frequency attenuation and should be corrected with empirical correction methods. This information presented here about different the diverse sensors be considered by investigators when choosing a sensor for a site or when analyzing EC measurements from multiple sites.

• Research Organization: Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER)
• Grant/Contract Number: AC02-05CH11231
• OSTI ID: 1580842
• Journal Information: Agricultural and Forest Meteorology, Vol. 272-273, Issue C; ISSN 0168-1923
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
Eddy covariance
Carbon dioxide
Water vapor
Gas analyzer
Spectral correction
Frequency loss
Data quality