Postdoctoral Researcher (M/F): Parameterization of vertical mixing associated with convection

Job Description

Missions

This postdoctoral position is part of the ANR PUMP research project (2025–2028), which aims to improve understanding of oceanic mixing mechanisms in the surface layers of the equatorial Atlantic and their contribution to energy exchanges (i.e., momentum and heat) between the ocean and the atmosphere, with a particular focus on the parameterization of vertical mixing associated with convection and diurnal variability in numerical models. Heat and momentum exchanges between the ocean and the atmosphere are central to the functioning of the climate system. Their realistic representation in ocean models remains a major challenge and relies on an accurate depiction of the dynamical and thermodynamical processes within the oceanic mixed layer. However, the representation of this ocean dynamics is highly sensitive to the characteristics of vertical mixing schemes and remains to date poorly evaluated due to a significant lack of suitable observations.

Vertical mixing is governed by two distinct processes: diffusion and convection. In most current ocean models, convection is not explicitly represented and is instead indirectly parameterized through an arbitrary increase in the vertical diffusion coefficient (Enhanced Vertical Diffusion). This approximation attempts to represent a fundamentally non-local process using a diffusive mechanism that is not designed for this purpose, which can introduce significant biases in the representation of the vertical structure and ocean circulation.

In this context, a new unified approach to vertical mixing has been developed: the Eddy-Diffusivity Mass-Flux (EDMF) scheme, which combines local vertical diffusion with non-local convection. This scheme provides a more physically based representation of mixing processes and represents a major advance for oceanic and climate models. Global simulations using the NEMO model at 1/4° resolution have recently been carried out as part of a postdoctoral project (Mercator-Océan, CNRM). A detailed evaluation of the impacts of the EDMF scheme on ocean circulation and heat content was conducted, together with ad hoc adjustments of certain parameters. However, these empirical tunings have shown their limitations, and it now appears necessary to rely on more robust parameter optimization methods.

Activity

In the first phase, the objective of this new postdoctoral project will be to calibrate the key parameters of the EDMF scheme by implementing the semi-automatic High-Tune calibration method, which is more rational and systematic than empirical approaches. This calibration will be carried out using the global NEMO model at 1° resolution. The goal of this calibration work is to produce an optimized set of parameters, which will subsequently be used in the CNRM-CM and CNRM-ESM climate models as part of the CMIP7 exercise, as well as in the operational models run at Mercator-Océan-International (MOI).

In a second phase, the optimized version of the EDMF scheme will be further refined with a focus on the tropical Atlantic, using higher-resolution NEMO simulations (1/4°, 1/12°). The realism of these simulations will be assessed using recent observations from PIRATA moorings and Argo floats.

Your Profil

Skills

Education:
- PhD in Physical Oceanography or Atmospheric Sciences.

Skills:
- Strong experience in processing oceanographic data (in situ and satellite).
- Expertise in numerical modeling (e.g., ROMS, NEMO, CROCO, or equivalent).
- Proficiency in data analysis tools (Python, Matlab, or equivalent).
- Knowledge of equatorial dynamics and/or mixing processes.
- Strong scientific writing and communication skills (French and English).

Your Work Environment

The postdoctoral researcher will join a multidisciplinary team involving LEGOS, CNRM, and Mercator-Océan-International, engaged in several regional and international projects (PIRATA, NEMO, etc.). Working time will be divided between CNRM (60%) and LEGOS (40%). International collaborations will also be considered.

Compensation and benefits

Compensation

Between €3,041 and €4,216 gross per month, depending on experience.

Annual leave and RTT

44 jours

Remote Working practice and compensation

Pratique et indemnisation du TT

Transport

Prise en charge à 75% du coût et forfait mobilité durable jusqu’à 300€

About the offer

About the CNRS

The CNRS is a major player in fundamental research on a global scale. The CNRS is the only French organization active in all scientific fields. Its unique position as a multi-specialist allows it to bring together different disciplines to address the most important challenges of the contemporary world, in connection with the actors of change.

CNRS

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