Turbulence confuration used for ROMS open ocean domains

[patrick.hyder]

Hi ROMS users,

At the Met Office, we are trying to standardise and optimise our NEMO turbulence model and its configuration for our global ORCA025 and ORCA1 configurations. For this reason, if possible, we would like to find out what turbulence configurations other modelling groups are using, particularly with regard to:



1. Background or minimum diffusivity - in NEMO there are options to ramp down the minimum diffusivity towards the equator and to ramp it up exponentially with depth. Does anyone use either of these type of minimum diffusivity variations in ROMS open ocean simulations and, if so, is there an associated reference? We have also just started using in a tidal mixing parameterisation (derived empirically from tidal runs of ORCA025). We are therefore trying to optimise the use the tidal mixing parameterisation in combination with the ramp up with depth of minimum diffusivity and think that we should either reduce or not use the ramp up of minimum diffusion with depth when using the tidal mixing parameterisation. Does anyone use a tidal mixing parameterisation in ROMS and is there a relevant reference. Perhaps ROMS would always be run with tides so there is no need for this type of parameterisation?



2. Generic Length Scale (k-epsilon) or 2 equation mixing schemes - we have just started to try using the GLS closure scheme configured to k-E 2 equation TKE closure (used for shelf seas NEMO runs) for open ocean runs and have some initially promising results, although we have not completed full testing. Have anyone had any experience of using full two equation TKE closure models in open ocean configurations of ROMS and, if so, it is documented anywhere?



Many thanks for any help anyone can provide with these questions.



Best regards,
Pat