1D Ocean-Atmosphere Coupled Model Applied to a Diurnal Warm Layer Case

Aurore Voldoire, CNRM, Toulouse, France, Herve Giordani, CNRM-GAME, Toulouse Cedex 01, France, Romain Roehrig, CNRM (Météo-France and CNRS), Toulouse, France, Yunyan Zhang, Lawrence Livermore Nat Labs, Livermore, CA, United States, Shaocheng Xie, Lawrence Livermore Nat''l Lab, Livermore, CA, United States and Hugo Bellenger, JAMSTEC Japan Agency for Marine-Earth Science and Technology, Kanagawa, Japan
A unicolumn model coupling an atmospheric and an oceanic 1D models has been developed based on the CNRM-CM6-1 3D climate model (Voldoire et al., 2019). Such a configuration is useful to better understand the interactions between the ocean and atmospheric boundary layers. It also allows to evaluate in a more constrained framework the sensitivity of the coupling to the air-sea flux parameterisation, to the coupling frequency, to the solar flux ocean penetration parameterisation, etc.

This configuration has been first used to simulate a diurnal warm layer case derived from observations of the Cindy-Dynamo campaign close to the R/V Revelle ship. The realism of the simulated ocean mixed layer is assessed and the processes contributing to mixing in this layer in very stable cases are highlighted. The model is shown to be able to simulate a very realistic diurnal temperature range though with a delay in maximum daily temperature that can be reduced by increasing the coupling frequency. However, the rate of cooling at night is clearly underestimated in the model whereas it is better simulated using the Zeng and Beljaars (2005) surface skin temperature prognostic scheme.