The eddy covariance (EC) technique allows the calculation of the turbulent fluxes of momentum, energy and matter. CO2, energy and momentum fluxes are covered by this Instruction document. The main variables to be measured are horizontal and vertical wind speed, wind direction, CO2 and H2O density, and sonic temperature. Other variables used for the calculation of the fluxes but not directly linked to the EC measurement stage (e.g. air temperature and pressure), are included in the Instruction document of low frequency meteorological variables. Variables measured in vertical profiles and used to calculate the change in storage fluxes(e.g. CO2, H2O, CH4, N2O concentrations, air characteristics) are reported in a dedicated Instruction document. The present document deals with the application of EC measurements at ICOS stations, describing the steps needed from the installation of the sensors to the data collection, including maintenance, calibration and data submission. The info is contained in the following sections:

-System setup: in this section the sensors are described, and the steps to perform from the installation to the data collection illustrated. -Maintenance and calibration: in this section all the maintenance and calibration guidelines are described, including the general timeline and how to deal with repairs. -Submission: this is the section related to data preparation and submission to the ETC. It includes a summary of the submission workflow described in a dedicated document, and list all metadata and ancillary parameters to be sent to the ETC, and how to submit them

It is important to remind that the exact application of the protocol at station level must be also discussed with the ETC in order to reach agreed solutions for specific case.