Relevance of ERA40 dynamical downscaling for modeling deep convection in the Mediterranean Sea

A strong open-ocean convection event was observed in the Northwestern Mediterranean sea during the 1986-87 winter. This period was used as a case study to evaluate the impact of the spatial resolution of atmospheric forcing on deep convection modeling. Twin numerical experiments were performed with an oceanic model forced by atmospheric forcing sets with different resolutions. A low resolution atmospheric forcing extracted from the ERA40 reanalysis was compared with a high resolution forcing produced by a dynamical downscaling of ERA40. A high resolution climate model spectrally driven by ERA40 fields for the large scales provided the dynamical downscaling dataset covering the 1958-2001 period. The oceanic simulation performed under low resolution meteorological forcing did not reproduce the observed convection. The simulation performed under high resolution forcing correctly reproduced the convection event. This was principally due to the enhancement of spatial and temporal meteorological extremes under the high resolution forcing.