133 Quasi-LES simulation of a heavy precipitating Mesoscale Convective System Observed during the HyMeX Campaign

Wednesday, 9 November 2016
Broadway Rooms (Hilton Portland )
Fanny Duffourg, CNRM, Toulouse, France; and M. Martinet and O. Nuissier

The Mediterranean regions are regularly affected by heavy precipitation due to
Mesoscale Convective Systems. Large amounts of precipitation (often more than 100mm in
less than 12 hours) fall over small and steep river catchments causing devastating flash
floods. Our ability to predict such high-impact events remains limited because of the
influence of finescale processes and their nonlinear interactions with larger-scale processes.
The dedicated HyMeX field campaign was thus designed to improve the present state of
knowledge of Mediterranean HPEs and to improve their forecast by the numerical models.
The first Special Observing Period (SOP1) of the campaign took place in autumn 2012
(Ducrocq et al., 2014). More than 200 research instruments were deployed over the
northwestern Mediterranean Sea and its surrounding coastal regions in France, Italy, and
Spain. They ensured a close observation of the precipitating systems and provided a
finescale description of the upstream meteorological conditions over the sea.
In the present study, one of the HPE that affected Southeastern France during HyMeX
SOP1 is analysed to better understand the convective processes involved in the
development and maintenance of the heavy precipitating systems. The analysis is based
both on the campaign observations and numerical simulations of the event. The simulations
are performed with the French research model Meso-NH. This model shares its physical
parameterisations with the French operational model AROME. The horizontal resolution of
the simulations is increased from 2,5 km to 150m, thus avoiding the grey-zone of the
turbulence. The simulations run over a large grid covering the northwestern Mediterranean
basin in order to encompass the precipitating systems during their whole life-cycle as well as
the marine low-level moisture-supplying flow.
The HyMeX SOP1 observation dataset enables to evaluate the quality of the
simulations and is useful to validate the meteorological environment over the sea as well as
the convective processes simulated. A special attention is paid to the low-level circulation
and the moisture structures.
- Indicates paper has been withdrawn from meeting
- Indicates an Award Winner