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Ocean response to strong precipitation events in the Gulf of Lions (northwestern Mediterranean Sea): a sensitivity study

Abstract : The Mediterranean Sea is a region of intense air-sea interactions, with in particular strong evaporation over sea which drives the thermohaline circulation. The Mediterranean region is also prone to strong precipitation events characterized by low spatial extent, short duration, and high temporal variability. The impacts of intense offshore precipitation over sea, in the Gulf of Lions which is a spot for winter deep convection, are investigated using four sensitivity simulations performed at mesoscale resolution with the eddy-resolving regional ocean model NEMO-MED12. We use various atmospheric fields to force NEMO-MED12, downscaled from reanalyses with the non-hydrostatic mesoscale Weather Research and Forecasting model but differing in space resolutions (20 and 6.7 km) or in time frequencies (daily and three-hourly). This numerical study evidences that immediate, intense, and rapid freshening occurs under strong precipitation events. The strong salinity anomaly induced extends horizontally (~50 km) as vertically (down to 50 m) and persists several days after strong precipitation events. The change in the space resolution of the atmospheric forcing modifies the precipitating patterns and intensity, as well as the shape and the dynamics of the low-salinity layer formed are changed. With higher forcing frequency, shorter and heavier precipitation falls in the ocean in the center of the Gulf of Lions, and due to a stronger vertical shear and mixing, the low-salinity anomaly propagates deeper.
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https://hal.archives-ouvertes.fr/hal-00648137
Contributor : Cindy Lebeaupin Brossier Connect in order to contact the contributor
Submitted on : Monday, December 5, 2011 - 11:12:28 AM
Last modification on : Friday, December 3, 2021 - 11:34:11 AM

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Cindy Lebeaupin Brossier, Karine Béranger, Philippe Drobinski. Ocean response to strong precipitation events in the Gulf of Lions (northwestern Mediterranean Sea): a sensitivity study. Ocean Dynamics, Springer Verlag, 2012, 62 (2), pp.213-226. ⟨10.1007/s10236-011-0502-8⟩. ⟨hal-00648137⟩

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