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Stations HTM-NET et Météo-France dans l'étang de Berre et méthode de projection de la vitesse du vent dans l'axe du bassin.

Stations HTM-NET et Météo-France dans l'étang de Berre et méthode de projection de la vitesse du vent dans l'axe du bassin.

Citations

... The sea water density is calculated using the UNESCO seawater equation of state (UNESCO, 1979), using measured temperature and constant salinity (37.5 PSU). Considering the natural variability of lagoon salinity (15 to 45 PSU), this implies a water level computational bias lower 200 than 0.2 cm, which corresponds to the precision of the pressure measurements (Rey et al., 2020). ...
... Apart from the wind, the water levels at the two sites are affected by different forcings. been observed at the Berre lagoon: the seiching period along the NW-SE axis is approximately 100 minutes and has a maximum amplitude of 8 cm (Paugam et al., 2020). The EDF hydroelectric power station released few liquid inflows during the study period, these discharges have a uniform impact on water level throughout the lagoon. ...
... Sampling period at both station is 10 min.Water level data in Berre lagoon are provided by HTM-NET network (https://htmnet.mio.osupytheas.fr), a network of instruments providing long term air and water pressure and temperature measurements along the French south-east Mediterranean coast(Rey et al., 2020). The data used for the present study was recorded from March 2019 to August 2020 with a similar setup as for Vaccarès, 185 i.e. two pairs of piezometers (Keller PAA-36Xiw CTD). ...
Article
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The present paper is specifically focused on enclosed or semi-enclosed basins where the wind is the dominant driver of water surface tilting, leading to the so-called wind tide contributing to water levels rise. Wind-induced free surface tilting is studied using the 1-D steady form of the depth-averaged shallow water (Saint-Venant) momentum equation which reflects the depth-averaged local balance between surface slope and wind stress. Two contrasted field sites, the Berre and Vaccarès lagoons, have been monitored providing water level data along a reference axis. This study highlighted the occurrence of wind tides at the two field sites. The bimodal wind exposure ensured the robustness of the observations, with non-linear but symmetric behaviors patterns observed in winds from opposite directions. It is observed that the higher the wind speed, the steeper the slope of the free surface in accordance with the well known basic trend. In addition, a significant effect of depth is observed, with greater surface tilting in the shallower lagoon. The data analysis confirmed the robustness of such a simple approach in the present context. Using the additional assumption of constant, i.e. wind-independent, drag coefficients (CD) allowed a good match with the observations for moderate wind speeds for both sites. However, the depth effect required the CD to be increased in the shallower basin. Classical empirical wind-dependent CD parameterizations provide better wind-tide predictions than the constant-CD approach in very strong wind conditions but totally failed in predicting surface tilting in the shallower site, suggesting that physical parameters other than wind speed should be taken into account for the CD parameterization in very shallow lagoons.