Decomposing the role of dry intrusions for ocean evaporation during mistral

Yonatan Givon, Douglas Keller, Jr, Romain Pennel, Philippe Drobinski, Shira Raveh-Rubin

Research output: Contribution to journalArticlepeer-review

Abstract

The mistral is a northerly gap-wind regime blowing through the Rhone Valley in Southern France. It is held responsible for the sea-surface cooling necessary to produce deep convection in the Gulf of Lion through turbulent ocean heat loss. The mistral is tightly connected to lee-cyclogenesis in the Gulf of Genoa, where topography forces substantial downward motion. Dry intrusions (DIs) are airstreams forming the descending branch of extratropical cyclones. Known to induce cold and dry surface anomalies, DIs are potential contributors to enhanced surface evaporation during mistral. In this study, a climatological database (ERA-INTERIM, 1981–2016) of mistral–DI co-occurrence is constructed, allowing quantification of the impact of DIs on the mistral evaporative hot spot for the first time. We find that, on average, mistral–DI evaporation rates are doubled, compared to mistral without DIs. Moreover, cluster-composite analysis reveals amplifications exceeding 300% between dynamically similar mistral events, with response to DIs. Daily latent heat-flux anomalies in the Gulf of Lion are decomposed into contributions from the various parameters to analyse the mistral evaporation response to DIs. Mistral–DI events are shown to produce extreme evaporation rates through increased mistral wind speeds. The results highlight the downward momentum flux delivered by DIs to the mistral at the Gulf of Lion as the primary driver of the evaporation amplification mechanism. We further explore the variability between different mistral–DI events and conclude that extreme mistral–DI evaporation events are linked to descending air trajectories entering the Gulf of Lion at an early stage of their lifetimes. These DIs charge the mistral with maximum vertical momentum fluxes, which act to intensify surface winds and hence evaporation rates.
Original languageEnglish
Pages (from-to)1791-1808
Number of pages18
JournalQuarterly Journal of the Royal Meteorological Society
Volume150
Issue number760
DOIs
StatePublished Online - 19 Feb 2024

All Science Journal Classification (ASJC) codes

  • Atmospheric Science

Fingerprint

Dive into the research topics of 'Decomposing the role of dry intrusions for ocean evaporation during mistral'. Together they form a unique fingerprint.

Cite this