Open AccessImpact of the spatial distribution of the atmospheric forcing on water mass formation in the Mediterranean Sea
Author(s) -
Béranger Karine,
Drillet Yann,
Houssais MarieNoëlle,
Testor Pierre,
BourdalléBadie Romain,
Alhammoud Bahjat,
Bozec Alexandra,
Mortier Laurent,
BouruetAubertot Pascale,
Crépon Michel
Publication year - 2010
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2009jc005648
Subject(s) - forcing (mathematics) , mediterranean sea , mesoscale meteorology , climatology , water mass , geology , convection , environmental science , mediterranean climate , atmospheric model , sea surface temperature , oceanography , atmospheric sciences , meteorology , geography , archaeology
The impact of the atmospheric forcing on the winter ocean convection in the Mediterranean Sea was studied with a high‐resolution ocean general circulation model. The major areas of focus are the Levantine basin, the Aegean‐Cretan Sea, the Adriatic Sea, and the Gulf of Lion. Two companion simulations differing by the horizontal resolution of the atmospheric forcing were compared. The first simulation (MED16‐ERA40) was forced by air‐sea fields from ERA40, which is the ECMWF reanalysis. The second simulation (MED16‐ECMWF) was forced by the ECMWF‐analyzed surface fields that have a horizontal resolution twice as high as those of ERA40. The analysis of the standard deviations of the atmospheric fields shows that increasing the resolution of the atmospheric forcing leads in all regions to a better channeling of the winds by mountains and to the generation of atmospheric mesoscale patterns. Comparing the companion ocean simulation results with available observations in the Adriatic Sea and in the Gulf of Lion shows that MED16‐ECMWF is more realistic than MED16‐ERA40. In the eastern Mediterranean, although deep water formation occurs in the two experiments, the depth reached by the convection is deeper in MED16‐ECMWF. In the Gulf of Lion, deep water formation occurs only in MED16‐ECMWF. This larger sensitivity of the western Mediterranean convection to the forcing resolution is investigated by running a set of sensitivity experiments to analyze the impact of different time‐space resolutions of the forcing on the intense winter convection event in winter 1998–1999. The sensitivity to the forcing appears to be mainly related to the effect of wind channeling by the land orography, which can only be reproduced in atmospheric models of sufficient resolution. Thus, well‐positioned patterns of enhanced wind stress and ocean surface heat loss are able to maintain a vigorous gyre circulation favoring efficient preconditioning of the area at the beginning of winter and to drive realistic buoyancy loss and mixing responsible for strong convection at the end of winter.