Air-sea interactions and coupling in Mediterranean torrential rain events
The Mediterranean Sea is an important source of heat and moisture for the heavy precipitating events that often occur over the Mediterranean basin in autumn. Within the CYPRIM project framework, the sensitivity of these extreme events to the sea surface temperature and turbulent fluxes parameterization have been examined on three cases based on high-resolution atmospheric simulations (2-3 km). The extreme precipitating events considered were: the 12-13 Nov. 1999 event over Aude, the 8-9 Sept. 2002 over Gard and the 3 Dec. 2003 over Hérault. For the two first cases, most of the precipitation were attributed to quasi-stationary MCSs, whereas the third case was characterised by a quasi-stationary frontal disturbance. Various SST fields have been applied (analysed SST, satellite SST products, increased/decreased analysed SST) as surface conditions to the MESO-NH model. We also introduced two iterative bulk sea surface fluxes parameterizations in the surface scheme of MESO-NH (SURFEX); the first includes a multi-campaign calibration of the exchange coefficients (unified parameterization or UNITFP), the other one corresponds to the Fairall et al., 2003's algorithm (COARE 3.0). The main results are first the significant impact on the atmospheric convection intensity and location of the overall SST value beneath the low-level jet; secondly a strong decrease of the wind stress and of the evaporation simulated when the UNITFP and COARE 3.0 parameterizations are used instead of the standard MESO-NH/SURFEX parameterization.
An air-sea coupling between the MESO-NH model and the 1D oceanic model based on Gaspar et al. (1990) is currently developed in order to study the impact of heavy precipitation and associated strong wind stress on the Mediterranean Sea mixed layer.
HyMeX – Hydrological cycle in the Mediterranean Experiment 2010-2020