Eddy covariance flux measurements over a man made lake during the ALEX 2014 field campaign in South Portugal

Energy, vapor, CO2 and momentum exchanges between water and air were measured using the new IRGASON eddy covariance system, an integrated open-path CO2 /H2O Gas Analyser and 3D Sonic Anemometer, installed on a instrumented floating platform (Figure 1) in the Alqueva reservoir, a large man made lake (area of 250 km2) in South Portugal. Radiation sensors were also mounted on the raft in order to measure near surface up and down radiative fluxes, while the water temperature profile below the platform were continuously archived. An accelerometer was mounted on the support bar near the sonic anemometer in order to correct the vertical component of the wind due to the the raft swing. The measurements were performed during the ALqueva hydro-meteorological EXperiment, ALEX 2014, between June and September 2014. ALEX 2014 ( http://www.alex2014.cge.uevora.pt) was an integrated field campaign with measurements of chemical, physical and biological parameters at different experimental sites in the reservoir and in its surrounding area. Worldwide, there are few reported flux measurements over lakes. This set of observations contribute to improve the characterization of the exchanges between a lake and the atmosphere in a semi-arid climate. The eddy covariance estimates of lake evaporation are compared against other methods.