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Abstract:
The Integrated Carbon Observation System Research
Infrastructure aims to provide long-term, continuous observations
of sources and sinks of greenhouse gases such as carbon
dioxide, methane, nitrous oxide, and water vapour. At ICOS
ecosystem stations, the principal technique for measurements of
ecosystem-atmosphere exchange of GHGs is the eddy-covariance
technique. The establishment and setup of an eddy-covariance
tower have to be carefully reasoned to ensure high quality flux
measurements being representative of the investigated ecosystem
and comparable to measurements at other stations. To fulfill
the requirements needed for flux determination with the eddycovariance
technique, variations in GHG concentrations have
to be measured at high frequency, simultaneously with the wind
velocity, in order to fully capture turbulent fluctuations. This
requires the use of high-frequency gas analysers and ultrasonic
anemometers. In addition, to analyse flux data with respect to
environmental conditions but also to enable corrections in the
post-processing procedures, it is necessary to measure additional
abiotic variables in close vicinity to the flux measurements. Here
we describe the standards the ICOS ecosystem station network
has adopted for GHG flux measurements with respect to the setup
of instrumentation on towers to maximize measurement precision
and accuracy while allowing for flexibility in order to observe specific ecosystem features.
