Interactions lake-atmosphere: The ALEX 2014 field campaign and numerical simulations

The ALqueva hydro-meteorological EXperiment, ALEX 2014, was an integrated field campaign with measurements of chemical, physical and biological parameters in water and air at different experimental sites in the region of the Alqueva reservoir, a 250 km2 man made lake, in the southeast of Portugal. The Field campaign took place from June 1 to September 30, 2014 and comprises an Intensive Observation Period (IOP) of three days (22 to 24 July). During the four months, the over water fluxes of momentum, heat and mass (H2O and CO2) were obtained with an integrated Open-Path CO2 /H2O Gas Analyser and 3D Sonic Anemometer, mounted on a floating platform, where radiative fluxes were also measured, as well as the water temperature profile. Eight near surface weather stations were operating in the area and air quality, atmospheric electrical field (Potential Gradient) and radon (222Rn) concentration were continuous monitored. Along this period, in situ measurements, water samples and biological elements were monthly collected from three fixed platforms placed in the lacustrine zone and from selected sites in the margins. During the IOP, radiosondes were launched every tree hours, allowing a characterization of the atmospheric boundary layer and its evolution. In 10 occasions Geigersondes were coupled to the radiosondes in order to obtain the atmospheric ionization profile. The boundary layer was characterized with a Ceilometer and the vertical distribution of O3 and NO2 were obtained from a Spectrometer. A GPS network of 15 GNSS stations was installed in order to map the water vapour. The sky brightnesson the nights of July 24 and 25, was measured using a Sky Quality Meter. The lake-atmosphere interactions and its impact in the boundary layer structure and in the local circulations are studied using data collected during the ALEX 2014 POI together with results from numerical simulations performed with the non-hydrostatic Meso-NH french model

ALEX2014: The Alqueva Hydro-Meteorological Experiment

During the four months of the ALEX 2014, the over water fluxes of momentum, heat and mass (H2O and CO2) were obtained with an integrated Open-Path CO2 /H2O Gas Analyser and 3D Sonic Anemometer, mounted on a floating platform (Fig.1) belonging to the Portuguese Environment Agency. The short and long wave, up and down, radiative fluxes were measured at the same place, as well as the water temperature profile. Eight near surface weather stations were operating during the field campaign, two in floating platforms and one in a little island. The air quality, the atmospheric electrical field (Potential Gradient) and the radon (222Rn) concentration were continuous monitored. The solar direct normal irradiation (DNI) as well as other solar radiation components were also measured. Along this period, in situ measurements, water sam-ples and biological elements were monthly collected from three fixed platforms placed in the lacustrine zone and from selected sites in the margins. In each campaign, the vertical profiles of temperature, dis-solved oxygen (mg DO L-1 and %), pH, oxidation-reduction potential, turbidity and solar inwater irra-diation were taken. Simultaneously, water samples were collected at three depths for nutrient determina-tion and microscopic and molecular characterization of cyanobacteria. Diatoms were collected from artificial substrates placed in the platforms and Chironomid pupal exuviae were sampled from two selected sites on the reservoir margins During the IOP, 18 balloons with meteorological radiosondes were launched. In 10 occasions Geigersondes were coupled to the radiosondes in order to obtain the atmospheric ionization profile. The boundary layer was characterized with a Ceilometer and the vertical distribution of O3 and NO2 were obtained from a Spectrometer. A GPS network of 15 GNSS stations was installed in order to map the water vapour. The sky brightness on the nights of July 24 and 25, was measured using a Sky Quality Meter