DATE2022-05-17 16:02:57
TITLEThe Mistral wind: large-scale controlling mechanisms and impact on evaporation from the Mediterranean Sea
AUTHORSYonatan Givon (1) ,Shira Raveh-rubin (1) ,Douglas Keller Jr. (2) ,Philippe Drobinski (2) ,Romain Pennel (2) ,Vered Silverman (1)
  1. 1) Wiezmann Institute Of Science, Rehovot (Israel) ,2) Ecole Polytechnique, Palaiseau (France)
ABSTRACTThe Mistral is a low level, northerly wind blowing through the Rhone Valley and towards the Gulf of Lion (GOL). Accompanied with a Genoa cyclone, Mistral events are often associated with severe weather is southern France, with impacts varying from extreme wind gusts and rainfall to severe wildfire outbursts. While the Mistral wind and its impacts have long been studied in the mesoscale context, the synoptic and large-scale dynamics controlling the Mistral wind are still unclear. Specifically, the synoptic-scale upper-tropospheric conditions dictating the Mistral’s duration, amplitude and frequency have not been identified and quantified. In this study, using ERA5 reanalysis and a combined Eulerian-Lagrangian investigation, we demonstrate that the onset of severe Mistral cases can be linked to a synoptic-scale dry intrusion (DI). Such DI airstreams initiate in the upper troposphere at high latitudes and descend slantwise into the Rhone Valley and out to the GOL. Different classes of upper-tropospheric troughs are conductive for DI flows that govern the Mistral characteristics. The DI outflows are accompanied by surface cooling, drying, wind acceleration and intense surface latent heat fluxes. The intense evaporation is potentially conductive for the seasonal buildup of dense water formation, thereby impacting the Mediterranean overturning circulation.