Gap filling strategies for defensible annual sums of net ecosystem exchange

Research output: Contribution to journalResearch articleContributedpeer-review

Contributors

  • Eva Falge - , University of California at Berkeley, University of Bayreuth (Author)
  • Dennis Baldocchi - , University of California at Berkeley (Author)
  • Richard Olson - , Oak Ridge National Laboratory (Author)
  • Peter Anthoni - , Oregon State University (Author)
  • Marc Aubinet - , University of Liege (Author)
  • Christian Bernhofer - , Chair of Meteorology (Author)
  • George Burba - , University of Nebraska-Lincoln (Author)
  • Reinhart Ceulemans - , University of Antwerp (Author)
  • Robert Clement - , University of Edinburgh (Author)
  • Han Dolman - , Wageningen University & Research (WUR) (Author)
  • André Granier - , INRAE - National Institute of Agricultural Research (Author)
  • Patrick Gross - , INRAE - National Institute of Agricultural Research (Author)
  • Thomas Grünwald - , Chair of Meteorology (Author)
  • David Hollinger - , United States Department of Agriculture (Author)
  • Niels Otto Jensen - , Technical University of Denmark (Author)
  • Gabriel Katul - , Duke University (Author)
  • Petri Keronen - , University of Helsinki (Author)
  • Andrew Kowalski - , University of Antwerp (Author)
  • Chun Ta Lai - , Duke University (Author)
  • Beverley E. Law - , Oregon State University (Author)
  • Tilden Meyers - , NOAA/ATDD (Author)
  • John Moncrieff - , University of Edinburgh (Author)
  • Eddy Moors - , Wageningen University & Research (WUR) (Author)
  • J. William Munger - , Harvard University (Author)
  • Kim Pilegaard - , Technical University of Denmark (Author)
  • Üllar Rannik - , University of Helsinki (Author)
  • Corinna Rebmann - , Max Planck Institute for Biogeochemistry (Author)
  • Andrew Suyker - , University of Nebraska-Lincoln (Author)
  • John Tenhunen - , University of Bayreuth (Author)
  • Kevin Tu - , University of New Hampshire (Author)
  • Shashi Verma - , University of Nebraska-Lincoln (Author)
  • Timo Vesala - , University of Helsinki (Author)
  • Kell Wilson - , NOAA/ATDD (Author)
  • Steve Wofsy - , Harvard University (Author)

Abstract

Heightened awareness of global change issues within both science and political communities has increased interest in using the global network of eddy covariance flux towers to more fully understand the impacts of natural and anthropogenic phenomena on the global carbon balance. Comparisons of net ecosystem exchange (FNEE) responses are being made among biome types, phenology patterns, and stress conditions. The comparisons are usually performed on annual sums of FNEE; however, the average data coverage during a year is only 65%. Therefore, robust and consistent gap filling methods are required. We review several methods of gap filling and apply them to data sets available from the EUROFLUX and AmeriFlux databases. The methods are based on mean diurnal variation (MDV), look-up tables (LookUp), and nonlinear regressions (Regr.), and the impact of different gap filling methods on the annual sum of FNEE is investigated. The difference between annual FNEE filled by MDV compared to FNEE filled by Regr. ranged from -45 to +200 g C m-2 per year (MDV-Regr.). Comparing LookUp and Regr. methods resulted in a difference (LookUp-Regr.) ranging from -30 to +150 g C m-2 per year. We also investigated the impact of replacing measurements at night, when turbulent mixing is insufficient. The nighttime correction for low friction velocities (u*) shifted annual FNEE on average by +77 g C m-2 per year, but in certain cases as much as + 185 g C m-2 per year. Our results emphasize the need to standardize gap filling-methods for improving the comparability of flux data products from regional and global flux networks.

Details

Original languageEnglish
Pages (from-to)43-69
Number of pages27
JournalAgricultural and forest meteorology
Volume107
Issue number1
Publication statusPublished - 1 Mar 2001
Peer-reviewedYes

External IDs

ORCID /0000-0003-2263-0073/work/163765999

Keywords

Keywords

  • AmeriFlux, Data filling, Eddy covariance, EUROFLUX, F, FLUXNET, Interpolation techniques