htau_scaling

[jdha]

in 4.2.1 there is a namelist variable htau_scaling that doesn't appear in the code. It isn't present in 4.0.4 and it also doesn't appear in 4.2.2. Not sure where it's come from.

[atb299]

@jdha, it is part of the Southern Ocean package that went into GOSI9:

" Tuning of the e-folding length scale nn_htau associated with the parameterisation of near-inertial wave breaking resulted in the choice of a larger length scale in the Southern Ocean \citep[Fig. 2]{Storkey2018} where summertime climatological \citep{DeBoyerMontegut2004} mixed layers are on average deeper than in the northern latitudes. Revisiting this work we found that reducing the mixing depth between 10$^{\circ}$ and 40$^{\circ}$ S improved the warm subsurface bias in the Indian Ocean. The changes were tested in the forced eORCA025 GOSI9 configuration before being implemented as standard in the three GOSI9 configurations. "

All references to it are (I believe) in zdftke.F90:

zdftke.F90: REAL(wp) :: rn_htau_scaling ! a acaling factor to apply to the penetration of TKE zdftke.F90: & rn_htau_scaling , & zdftke.F90: WRITE(numout,) ' scaling factor for tke penetration depth rn_htau_scaling = ', rn_htau_scaling zdftke.F90: htau(:,:) = rn_htau_scaling10._wp zdftke.F90: htau(ji,jj) = MAX( 0.5_wp, MIN( 30._wp, 45._wp rn_htau_scalingABS( SIN( rpi/180._wp gphit(ji,jj) ) ) ) ) zdftke.F90: htau(ji,jj) = MAX( 0.5_wp, MIN( 10._wp, 45._wp rn_htau_scalingABS( SIN( rpi/180._wp gphit(ji,jj) ) ) ) ) zdftke.F90: htau(ji,jj) = MAX( 0.5_wp, MIN( 10._wp, 45._wp rn_htau_scalingABS( SIN( rpi/180._wp * gphit(ji,jj) ) ) ) )

[jdha]

@atb299 - yes I realise its purpose ... this was just a ticket to workout how I manage to include it into the namelist_ref for 4.2.1 and it not being in the code. I thought I'd just merged the NEMO 4.2.1 tag with SE-NEMO at 4.0.4 ... so I'm a little puzzled how it got into the namelist!

[atb299]

Is is because you use(d) GLS instead of TKE? If the code was there, you wanted to activate it you'd need to set nn_htau = 4 or 5 in the namelist. Looking at a GO6 namelist, I think a variant of the spatially varying TKE was present even at v3.6. As far as I can tell it is always set to rn_htau_scaling=1.0.

[jdha]

No we've used both - and when we've run with TKE we've run with nn_htau =4 ... In the 4.0.4 GO8 code we have there is no scaling applied using option 4

[jdha]

Ha! Just figured out what's happened (will confirm when ARCHER2 is back online). When I merged tag 4.2.1 and SE-NEMO 4.0.4 I also had an eye on the NPD 4.2.1. I think the fact you've edited SHARED/namelist_ref has probably thrown me - and that's where rn_htau_scaling has crept in. I tend to leave my SHARED directory untouched and any namelist mods based on MY_SRC go into an updated namelist_ref in the EXP dir. Will have to look again at the NPD and see if we can align SE-NEMO with NPD going forward!

[atb299]

Interesting, I use nn_htau = 5. I've just tracked that down to the change from GO8p7 to GOSI9p8 (see https://code.metoffice.gov.uk/trac/GO/wiki/GODocumentation/GO8.0/GO8Releases )

"4. The TKE mixing depth has been reduced. This change results in the deepening of the MLD in a band around 40S associated with a SST warming in winter and cooling in summer."

[jdha]

Closing for now. I've left rn_htau_scaling in the 4.2.2 namelist_ref but commented out. I will raise a further ticket addressing the streamlining of the code towards NPD after I've had a chat with @atb299 about the best way forward.