Joint Eddycovariance Project
This site is developed by a special interest group in
eddycorrelation. The group and its activities were initiated by Henk de
Bruin (Wageningen UR). The group is composed of researchers from:
- the Royal Netherlands Meteorological Institute (KNMI) in De
Bilt (Wim Kohsiek, Bart van den Hurk, Cor Jacobs and Fred Bosveld);
- Wageningen University, department of Meteorology and Air
Quality (WUR-METAIR) (Arjan van Dijk until April 2000, Henk de Bruin);
- Utrecht University, Institute for Marine and Atmospheric
Research Utrecht (IMAU) (Arjan van Dijk since May 2000).
The target of the special interest group is the development of
- Fundamental understanding of the eddycorrelation method.
There are large discrepancies between estimates for terms in the energy
balance at the surface obtained via eddycorrelation and estimates found
via other methods. With a fundamental basis of the eddycorrelation
method we will be better able to eliminate possible causes of
differences in observations. Furthermore we will be able to estimate
the consequences of certain assumptions for the accuracy of estimated
- A protocol for practical use of the eddycorrelation method,
including corrections for tilt, trends, distortion etcetera. Where
possible the protocol will be implemented in a software library.
Measurements which have been done and processed according to this
protocol will be more versatile in use. Researchers from different
groups can compare their results and conclusions, knowing that they
have processed their data equally. Consensus about a protocol will
facilitate future experiments by providing the conditions and
procedures, which have to be taken into account and followed during the
The Joint Eddycovariance Project is meant to provide the
basics of the eddy-correlation method plus an implementation in
practice. Researchers are encouraged to send suggestions / comments /
software / improvements that will allow us to improve on the present
collection and thus succeed in our goal: making and updating a state
of the art guideline and software implementation for eddycovariance
Our insights are collected in a report. The theory of the
eddy-covariance method is deployed in chapter 1. Here the surface
fluxes of sensible heat, water vapour, momentum and scalar densities
are related to measurable quantities at a finite height above the
ground. This is done via continuity and budget equations. In chapter 2
these relations are worked out for practical purposes. A step-by-step
recipe is provided for datareduction of eddy-covariance measurements.
The software implementation of this recipe in package ECPACK is
presented in chapter 3. The report is available as a PDF:
The report was mainly prepared by Arjan van Dijk while at
Wageningen University (except for the part on the planar fit method and
corrections for flow distortion using 3D ellipsoids).
The FORTRAN routines, which implement all steps from the
report in practice have been collected in a software library ECpack, and are available for download,
along with a two sample programs:
The source code is made available under the GNU Public Licence. The
routines are functionally separated, which means that the IO-routines
are neither integrated with the routines that e.g. estimate tilt-angles
nor with the routines that apply corrections to a dataset. Researchers
who are looking for routines that 'just give them that angle' are
welcome to proceed, but we also serve the poor soul who needs an
integrated routine doing all the tricks in one go.
- ec_ncdf, which can be used to process raw eddy-covariance data applying a wide range of corrections (data are assumed to be stored in NetCDF format; csi2ncdf can be used to prepare data stored in other formats)
- planang, which is used to calculated planar fit angles (the output of which can be used by ec_ncdf)
The software is free, but in order to keep track of who is using it (to notify you of updates and bug-fixes), with what equipment, and under what
type of conditions, we ask you to send us some details, stating:
Please send this information to firstname.lastname@example.org and you will get ASAP the correct URL to get the software.
What we have available for users are the entire source-code + executables for Windows.
If you have already registered with us, you know the address where to get those.
- Brand and type of equipment (sonic, thermometer, hygrometer, CO2-analyzer, other)
- What are the typical conditions, surface types where you perform your eddy-covariance measurements
In case you use our software in any publication, please acknowledge us by citing the the internal report: Van Dijk, A., Moene, A.F., and De Bruin, H.A.R., 2004: The principles of surface flux physics: theory, practice and description of the ECPACK library, Internal Report 2004/1, Meteorology and Air Quality Group, Wageningen University, Wageningen, the Netherlands, 99 pp.
For any information about this project, suggestions, comments,
Meteorology and Air Quality Group
Wageningen University and Research
6708 PB Wageningen
NL - 6708 BP Wageningen
Phone: (+31) 317 482604
Fax: (+31) 317 482811