Description du poste

The post-doctoral position is part of the CASSIOWPE R&D project dedicated to “Characterizing the Atmosphere and Sea Surface Interactions for the deployment of Offshore Wind in the Gulf of Lion’s Physical Environment”. This project is coordinated by FEM and aims, in particular to implement and improve an Ocean-Wave-Atmosphere (OWA) coupled system to refine the description of the Gulf of Lion meteocean conditions with future application to the wind resource assessment and design conditions of the Floating Offshore Wind Turbines, soon to be deployed in the area.
Within this project, the post-doctoral fellow will contribute to the improvement of the representation of the Marine Atmospheric Boundary Layer (MABL) and turbulent fluxes in atmospheric models by developing and testing a parameterization of the impact of sea sprays. An integrated approach is proposed to take advantage of our wave-atmosphere numerical coupled framework. Existing parameterizations of the impact of sea sprays on the turbulent fluxes are based on sea-spray generation functions. However, a large scatter exists on the current generation functions for large droplets exacerbating uncertainties on the sea-spray effect on heat and momentum air-sea exchanges (Veron, 2015). Most generation functions use wind speed as a proxy, but recent studies (Mueller and Veron 2009, Ovadnevaite et al. 2014) suggest generation functions built on more fundamental parameters like whitecap fraction, sea state or length of breaking fronts. In this project, we will take advantage of new sea-spray measurements either in situ or in laboratory tanks made available by our partners (J. Piazzola at MIO, F. Veron at Un. Delaware) and of the parameterization of breaking wave statistics currently developed in other FEM projects to develop a new air-sea fluxes parameterization taking into account the effect of sea spray. This parameterization, based on a new sea-spray generation function will be implemented in the surface module SURFEX (Masson et al., 2013) used in operational and research models at Meteo-France. Then, the Meso-NH atmospheric model (Lac et al., 2018), which is coupled with SURFEX, will be used on case studies of strong wind and various wave conditions in the Gulf of Lion (GoL). Mistral and Tramontane winds generate short, steep waves with a large proportion of breaking waves while typical storm sea state consists in longer waves and swell (e.g. Sauvage et al., 2020). The successful post-doctoral fellow will benefit from the development of a specific configuration of Ocean Wave Atmosphere modelling system and a selection of case studies for testing and tuning the parameterization, a work performed in the CASSIOWPE project.

Missions
The missions of the post-doctoral fellow will be to:
1) review and evaluate the existing parameterizations using information from recent sea-spray observation datasets (collaboration H. Branger, with J. Piazzola, and F. Veron; this should include one or two short stays at MIO / Un. Delaware),
2) develop a sea-spray generation function fitting these datasets and including a sea-state dependency,
3) develop the corresponding parameterization (bulk algorithm) for air-sea turbulent fluxes, based on existing parameterizations, in the SURFEX module,
4) test and tune it off line first, then using the fully CASSIOWPE OWA coupled system on realistic case studies selected in the first part of the CASSIOWPE project,
4) analyze the results,
5) disseminate the results (write publications for research journals, participate to international conference).
FEM and LOPS (Laboratoire d’Océanographie Physique et Spatiale) are looking for a highly motivated candidate eager to develop an innovative air-sea fluxes parameterization and to interact with the other members of the consortium. The candidate will have the opportunity to work with a state-of-the-art OWA coupled system to perform kilometer-scale simulations of strong wind conditions (Mistral, Tramontane or Mediterranean storms) in the highly variable environment of the GoL. The OWA configuration used to test and tune the parameterization is based on the atmospheric model Meso-NH (Lac et al., 2018), the wave model WW3 (Tolman, 2016) and the ocean model CROCO/ROMS (Shchepetkin and McWilliams, 2005, Debreu et al., 2012) using the coupling interface developed by Voldoire et al. (2017). The proposing team has a strong expertise in using this type of coupling system, a very good understanding of the air-sea exchanges, wave effects and physics of the MABL, as well as a good knowledge of the GoL’s environment.

Modalités de candidature

Expected starting date: October 2020
Duration: 24 month contract
Employer: France Energies Marines, 525 Av de Rochon, F-29280 Plouzané
The postdoc will spend about 80% of his time at LOPS/IFREMER:
1625 Route de Sainte-Anne, 29280 Plouzané, FRANCE
Final date for applications: August 28, 2020.
In case of an expected secondment of the candidate by a member of France Energies Marines, the application should mention the agreement of the present employer.

Please send your CV and cover letter to the following email address: contact@ite-fem.org. For scientific information, please contact : nbouin@ifremer.fr, jlredels@ifremer.fr, fabien.lecker@ite-fem.org and jean.francois.filipot@ite-fem.org.