Wrong namelist double diffusion mixing parameter name

[Robin_Waldman]

Context

I am currently checking the activation of the EVD scheme in the case of differential T-S mixing, either due to the double-diffusion mixing parametrization or to the new De Lavergne tidal mixing parametrization. Tests are done with NEMOMED12 configuration in the Mediterranean Sea.

Analysis

• The double diffusion mixing parametrization has 2 namelist parameters, one of which is wrongly named. rn_hsbfr is actually not the buoyancy flux ratio (constant=0.7 in zdfddm.F90) but the critical density ratio Rc, above which double diffusion rapidly decays.
• Also, the activation of key_zdftmx_new imposes the activation of the double diffusion mixing parametrization, which is not necessarily desired.

Recommendation

• Rename rn_hsbfr as rn_cdr for critical density ratio, and if useful introduce a new namelist parameter rn_hsbfr with default value 0.7.
• Introduce a logical in the namzdf_ddm section to activate or not double diffusion mixing when key_zdfddm is activated.

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