Record Details

Technical note: Time lag correction of aquatic eddy covariance data measured in the presence of waves

ScholarsArchive at Oregon State University

Field Value
Title Technical note: Time lag correction of aquatic eddy covariance data measured in the presence of waves
Names Berg, P. (creator)
Reimers, C. E. (creator)
Rosman, J. H. (creator)
Huettel, M. (creator)
Delgard, M. L. (creator)
Reidenbach, M. A. (creator)
Özkan-Haller, H. T. (creator)
Date Issued 2015 (iso8601)
Note This is the publisher’s final pdf. The published article is copyrighted by the author(s) and published by Copernicus Publications on behalf of the European Geosciences Union. The published article can be found at: http://www.biogeosciences.net/
Abstract Extracting benthic oxygen fluxes from eddy covariance
time series measured in the presence of surface
gravity waves requires careful consideration of the temporal
alignment of the vertical velocity and the oxygen concentration.
Using a model based on linear wave theory and
measured eddy covariance data, we show that a substantial
error in flux can arise if these two variables are not
aligned correctly in time. We refer to this error in flux as
the time lag bias. In one example, produced with the wave
model, we found that an offset of 0.25 s between the oxygen
and the velocity data produced a 2-fold overestimation
of the flux. In another example, relying on nighttime data
measured over a seagrass meadow, a similar offset reversed
the flux from an uptake of -50 mmolm⁻² d⁻¹ to a release
of 40 mmolm⁻² d⁻¹. The bias is most acute for data measured
at shallow-water sites with short-period waves and low
current velocities. At moderate or higher current velocities
(>5–10 cm s⁻¹/, the bias is usually insignificant. The widely
used traditional time shift correction for data measured in
unidirectional flows, where the maximum numerical flux is
sought, should not be applied in the presence of waves because
it tends to maximize the time lag bias or give unrealistic
flux estimates. Based on wave model predictions and
measured data, we propose a new time lag correction that
minimizes the time lag bias. The correction requires that the
time series of both vertical velocity and oxygen concentration
contain a clear periodic wave signal. Because wave motions
are often evident in eddy covariance data measured at
shallow-water sites, we encourage more work on identifying
new time lag corrections.
Genre Article
Access Condition http://creativecommons.org/licenses/by/3.0/us/
Identifier Berg, P., Reimers, C. E., Rosman, J. H., Huettel, M., Delgard, M. L., Reidenbach, M. A., & Özkan-Haller, H. T. (2015). Technical note: Time lag correction of aquatic eddy covariance data measured in the presence of waves. Biogeosciences, 12 (22), 6721-6735. doi:10.5194/bg-12-6721-2015

© Western Waters Digital Library - GWLA member projects - Designed by the J. Willard Marriott Library - Hosted by Oregon State University Libraries and Press