skip to main content

DOE PAGESDOE PAGES

Title: Addressing a systematic bias in carbon dioxide flux measurements with the EC150 and the IRGASON open-path gas analyzers

Across a global network of eddy covariance flux towers, two relatively new open-path infrared gas analyzers (IRGAs), the IRGASON and the EC150, are increasingly used to measure net carbon dioxide (CO 2) fluxes (F c_OP). Differences in net CO 2 fluxes derived from open- and closed-path IRGAs in general remain poorly constrained. In particular, the performance of the IRGASON and the EC150 for measuring F c_OP has not been characterized yet. These IRGAs measure CO 2 absorption, which is scaled with air temperature and pressure before converting it to instantaneous CO 2 density. This sensor-internal conversion is based on a slow-response thermistor air temperature measurement. In this paper, we test if the high-frequency temperature attenuation causes selectively systematic F c_OP errors that scale with kinematic temperature fluxes. First, we examine the relationship between wintertime F c_OP and kinematic temperature fluxes for eight northern ecosystems. Second, we investigate how residuals between F c_OP and CO 2 fluxes from co-located closed-path IRGAs (F C_CP) are related to kinematic temperature fluxes for three different ecosystem types (i.e., boreal forest, grassland, and irrigated cropland). We find that kinematic temperature fluxes, but not mean ambient air temperatures or CO 2 flux regime, consistently determine themore » absolute magnitude of F c_OP errors. This selectively systematic bias causes the most pronounced relative F c_OP errors to occur when “true” CO 2 fluxes are low and kinematic temperature fluxes are high (e.g., northern ecosystems during the winter). The smallest relative errors occur during periods with large “true” CO 2 fluxes and low kinematic temperature fluxes. To address this bias, we replace the slow-response air temperature in the absorption-to-CO 2 density conversion with a fast-response air temperature derived from sonic anemometer measurements. The use of the fast-response air temperature improves the agreement between half-hourly F c_OP and F C_CP for all open- versus closed-path IRGA comparisons. Additionally, cumulative F c_OP and F c_CP sums are more comparable as differences drop from 63 %–13 % to 20 %–8 %. Finally, the improved IRGASON and EC150 performance enhances the ability and confidence to synthesize flux measurements across multiple sites including these two relatively new IRGAs.« less
Authors:
ORCiD logo [1] ;  [1] ;  [1] ; ORCiD logo [2] ;  [3] ;  [2] ;  [4] ;  [5] ;  [6] ;  [6] ;  [1]
  1. Univ. of Montréal, QC (Canada). Centre for Northern Studies (CEN). Dept. of Geography
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  3. Campbell Scientific, Logan, UT (United States)
  4. Univ. of Alaska, Fairbanks, AK (United States). Inst. of Arctic Biology
  5. Agriculture and Agri-Food Canada, Brandon, MB (Canada). Brandon Research and Development Centre
  6. Wilfrid Laurier Univ., Waterloo, ON (Canada). Cold Regions Research Centre
Publication Date:
Grant/Contract Number:
AC02-05CH11231
Type:
Accepted Manuscript
Journal Name:
Agricultural and Forest Meteorology
Additional Journal Information:
Journal Volume: 228-229; Journal ID: ISSN 0168-1923
Publisher:
Elsevier
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of Alaska, Fairbanks, AK (United States); Univ. of Montréal, QC (Canada); Agriculture and Agri-Food Canada, Brandon, MB (Canada); Wilfrid Laurier Univ., Waterloo, ON (Canada)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); United States Geological Survey (USGS); National Science Foundation (NSF); Natural Sciences and Engineering Research Council of Canada (NSERC); Fonds de recherche du Québec – Nature et technologies (FRQNT) (Canada); German Academic Exchange Service (DAAD)
Country of Publication:
United States
Language:
English
Subject:
47 OTHER INSTRUMENTATION; 54 ENVIRONMENTAL SCIENCES; carbon dioxide fluxes; eddy covariance; open-path infrared gas analyzer; systematic error; sensible heat; absorption
OSTI Identifier:
1471026
Alternate Identifier(s):
OSTI ID: 1398566

Helbig, M., Wischnewski, K., Gosselin, G. H., Biraud, S. C., Bogoev, I., Chan, W. S., Euskirchen, E. S., Glenn, A. J., Marsh, P. M., Quinton, W. L., and Sonnentag, O.. Addressing a systematic bias in carbon dioxide flux measurements with the EC150 and the IRGASON open-path gas analyzers. United States: N. p., Web. doi:10.1016/j.agrformet.2016.07.018.
Helbig, M., Wischnewski, K., Gosselin, G. H., Biraud, S. C., Bogoev, I., Chan, W. S., Euskirchen, E. S., Glenn, A. J., Marsh, P. M., Quinton, W. L., & Sonnentag, O.. Addressing a systematic bias in carbon dioxide flux measurements with the EC150 and the IRGASON open-path gas analyzers. United States. doi:10.1016/j.agrformet.2016.07.018.
Helbig, M., Wischnewski, K., Gosselin, G. H., Biraud, S. C., Bogoev, I., Chan, W. S., Euskirchen, E. S., Glenn, A. J., Marsh, P. M., Quinton, W. L., and Sonnentag, O.. 2016. "Addressing a systematic bias in carbon dioxide flux measurements with the EC150 and the IRGASON open-path gas analyzers". United States. doi:10.1016/j.agrformet.2016.07.018. https://www.osti.gov/servlets/purl/1471026.
@article{osti_1471026,
title = {Addressing a systematic bias in carbon dioxide flux measurements with the EC150 and the IRGASON open-path gas analyzers},
author = {Helbig, M. and Wischnewski, K. and Gosselin, G. H. and Biraud, S. C. and Bogoev, I. and Chan, W. S. and Euskirchen, E. S. and Glenn, A. J. and Marsh, P. M. and Quinton, W. L. and Sonnentag, O.},
abstractNote = {Across a global network of eddy covariance flux towers, two relatively new open-path infrared gas analyzers (IRGAs), the IRGASON and the EC150, are increasingly used to measure net carbon dioxide (CO2) fluxes (Fc_OP). Differences in net CO2 fluxes derived from open- and closed-path IRGAs in general remain poorly constrained. In particular, the performance of the IRGASON and the EC150 for measuring Fc_OP has not been characterized yet. These IRGAs measure CO2 absorption, which is scaled with air temperature and pressure before converting it to instantaneous CO2 density. This sensor-internal conversion is based on a slow-response thermistor air temperature measurement. In this paper, we test if the high-frequency temperature attenuation causes selectively systematic Fc_OP errors that scale with kinematic temperature fluxes. First, we examine the relationship between wintertime Fc_OP and kinematic temperature fluxes for eight northern ecosystems. Second, we investigate how residuals between Fc_OP and CO2 fluxes from co-located closed-path IRGAs (FC_CP) are related to kinematic temperature fluxes for three different ecosystem types (i.e., boreal forest, grassland, and irrigated cropland). We find that kinematic temperature fluxes, but not mean ambient air temperatures or CO2 flux regime, consistently determine the absolute magnitude of Fc_OP errors. This selectively systematic bias causes the most pronounced relative Fc_OP errors to occur when “true” CO2 fluxes are low and kinematic temperature fluxes are high (e.g., northern ecosystems during the winter). The smallest relative errors occur during periods with large “true” CO2 fluxes and low kinematic temperature fluxes. To address this bias, we replace the slow-response air temperature in the absorption-to-CO2 density conversion with a fast-response air temperature derived from sonic anemometer measurements. The use of the fast-response air temperature improves the agreement between half-hourly Fc_OP and FC_CP for all open- versus closed-path IRGA comparisons. Additionally, cumulative Fc_OP and Fc_CP sums are more comparable as differences drop from 63 %–13 % to 20 %–8 %. Finally, the improved IRGASON and EC150 performance enhances the ability and confidence to synthesize flux measurements across multiple sites including these two relatively new IRGAs.},
doi = {10.1016/j.agrformet.2016.07.018},
journal = {Agricultural and Forest Meteorology},
number = ,
volume = 228-229,
place = {United States},
year = {2016},
month = {8}
}