Ocean response to strong precipitation events in the Gulf of Lions (northwestern Mediterranean Sea): a sensitivity study
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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.
KeywordsStrong precipitation Mediterranean Sea Stratification Resolution impact
This work is a contribution to the MORCE-MED project funded by the GIS (Groupement d’Intérêt Scientifique) “Climat, Environnement et Société, with granted access to the HPC resources of IDRIS (under allocation i2009010227). The authors are grateful to Charles Deltel (LOCEAN, INRIA), Romain Bourdallé-Badie, and Jonathan Beuvier (Mercator-Ocean) for their useful help about the MED12 model. Finally, the authors would like to thank the two anonymous reviewers that help us to deeply improve this paper.
- Barnier B, Madec G, Penduff T, Molines J-M, Tréguier A-M, Le Sommer J, Beckmann A, Biastoch A, Böning C, Dengg J, Derval C, Durand E, Gulev S, Rémy E, Talandier C, Theetten S, Maltrud ME, McClean J, De Cuevas B (2006) Impact of partial steps and momentum advection schemes in a global ocean circulation model at eddy-permitting resolution. Ocean Dyn 56(5–6):543–567. doi: 10.1007/s10236-006-0082-1 Google Scholar
- Béranger K, Drillet Y, Houssais M-N, Testor P, Bourdalle-Badie R, Alhammoud B, Bozec A, Mortier L, Bouruet-Aubertot P, Crépon M (2010) Impact of the spatial distribution of the atmospheric forcing on water mass formation in the Mediterranean Sea. J Geophys Res 115:C12041. doi: 10.1029/2009JC005648 CrossRefGoogle Scholar
- Beuvier J, Sevault F, Herrmann M, Kontoyiannis H, Ludwig W, Rixen M, Stanev E, Béranger K, Somot S (2010) Modelling the Mediterranean Sea interannual variability during 1961-2000: focus on the Eastern Mediterranean Transient (EMT). J Geophys Res 115:C08517. doi: 10.1029/2009JC005850 CrossRefGoogle Scholar
- Drobinski P, Anav A, Lebeaupin Brossier C, Samson G, Stéfanon M, Bastin S, Baklouti M, Béranger K, Beuvier J, Bourdallé-Badie R, Coquart L, D’Andrea F, De Noblet-Ducoudré N, Diaz F, Dutay J-C, Ethé C, Foujols M-A, Khvorostiyanov D, Madec G, Mancip M, Masson S, Menut L, Palmieri J, Polcher J, Turquety S, Valcke S, Viovy N (2011) Model of the regional earth system (MORCE): application to process and climate studies in vulnerable regions. Environ Model Softw (submitted)Google Scholar
- Madec G (2008) NEMO ocean engine. Note du Pole de modélisation, Institut Pierre-Simon Laplace (IPSL), France, no 27, ISSN no 1288–1619Google Scholar
- Skamarock WC, Klemp JB, Dudhia J, Gill DO, Barker DM, Duda MG, Huang X-Y, Wang W, Powers JG (2008) A description of the advanced research WRF version 3. NCAR Tech. Note NCAR/TN-475+STR, 125 ppGoogle Scholar