How to Routinely Check an
Eddy Covariance System to
Ensure Normal Operation
LI-COR Technical Solutions
Most eddy covariance (EC) systems are deployed in remote
areas and exposed to harsh environmental conditions.
During years-to-decades of continuous operation, potential
issues related to contamination, power, animal damage,
lightning, and other natural events such as fog and precipitation could arise. Aging of the hardware and out-of-date
software can also become issues. In order to minimize data
loss, routinely checking your EC system should be part of
your maintenance plan. Considering time consumption
and effectiveness, here are our recommendations:
1.
Check CO2, H2O and CH4 (if applicable) mole fractions,
air temperature, air pressure, and analyzer signal strength
as often as possible through the GHG Windows interface
software, as shown below. This can be done remotely or at
the field site. The CO2 and CH4 mole fractions should be
near ambient during the daytime. Analyzer signal
strengths for LI-7500A/RS/LI-7200/RS’s should be
between 80 and 100 (or slightly over 100) and the LI-7700
signal strength should be greater than 20. Although CH4
data are valid when LI-7700 signal strength is above 10, it
is better to resolve the low signal strength (for example,
cleaning the mirrors) before it reaches the lower threshold.
2.
Check for warnings on the main and diagnostics pages as
often as possible. A warning symbol shows that the
component is in need of attention. In the example below,
the warning on the LI-7700 indicates the connection
between the LI-7550 analyzer interface unit and the
LI-7700 CH4 analyzer has dropped. In the “Diagnostics”
window, if “SERVICE” is indicated instead of “OK”, there
is a problem with the CO2/H2O gas analyzer system.
Continued on next page
3.
Check time series data from individual raw data files.
Download raw data at least monthly if possible. Follow
the steps below to open a single “.ghg” file (half-hour of
data) to check: a) sampling rate by looking at the time
stamps and total number of records, b) values of the
variables, and c) variances of the variables. If your
sampling rate is too low, you will not be able to get
accurate fluxes.
●
Copy and paste the last (i.e. the newest) ghg file to a
different folder.
● Rename the file extension name from “.ghg” to
“.zip”.
● Select the newly renamed zip file, right click your
mouse, and use the “Extract All…” function to
unzip the file.
● Open the “…AIU-xxxx.data” file in the unzipped
folder using a spreadsheet program like Excel, in
comma-delimited format.
4.
Check multiple “.ghg” files using LI-COR’s LI-7x00 File
Viewer for spikes, gaps, trends, and other anomalies. The
File Viewer software can look at months of data instantly.
5. Check flux results for any anomalies. Process raw data as
soon as possible using EddyPro (for Windows, or for
MAC. If you have a SmartFlux device, you can skip the
raw data processing and check flux results directly by
looking at the flux daily summary files.
If you see problems and cannot solve them by yourself,
please contact LI-COR Technical Support through email at
[email protected], online chat at:
https://www.licor.com/env/support/,
or by phone at 1-402-467-3576 or 800-447-3576 (toll free).
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Phone: +1-402-467-3576
Toll free: 800-447-3576
Fax: +1-402-467-2819
[email protected] • [email protected] • www.licor.com/env
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[email protected] • [email protected]
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[email protected] • [email protected]
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