impact of HF wind in TKE

[smasson]

Idea: take into account the impact of High Frequency winds in TKE.
These changes have consequences on 2 parts of TKE :

1) TKE surface boundary condition
2) TKE due to surface and internal wave breaking

The first part was strongly facilitated by the changes done in changeset:1695
We only needed to read an extra file in sbcblk_core. To do so, we added 2 new namelist parameters in namsbc_core:

• ln_taudif : logical flag if we want to read the contribution of High Frequency stress defined as "the mean of stress module - the module of mean stress" data. (default value is .false.)
  
• sn_tdif ... : the line line needed to read this new field
  

Note that if ln_taudif = .false., there is no need to read any new input file

For the second part (penetration in subsurface) we created a new case for nn_etau = 3
This case is the same as case 1 except that the quantity of energy that penetrates is no more "rn_efr * en" but the energy delivered y the High Frequency winds diagnosed as the difference between "the mean of stress module - the module of mean stress".
We added 2 namelist parameters associated to the case nn_etau = 3:

• rn_addhft : add offset applied to the "mean of stress module - module of mean stress" (always kept > 0) (default = 0.)
  
• rn_sclhft : scale factor applied to the "mean of stress module - module of mean stress" (default = 1.)
  

These 2 parameters are applied in zdftke to the zdif = "the mean of stress module - the module of mean stress":

zdif = rn_sclhft * MAX( 0.e0, zdif + rn_addhft )

The appropriate values of these parameters are not yet really defined... As a first guess, we propose rn_addhft = -1.e-3 and rn_sclhft = 1.
Note that we suggest to combine nn_etau = 3 with the new case nn_htau = 2 corresponding to a constant penetration depth of 30m

Note:

• we add a new logical in sbc_oce: lhftau which is set to .true. if the HF tau information is provided (sbcblk_core with ln_taudif = .true. or cn_rcv_taumod = 'coupled' in coupled mode). lhftau must be .true. if nn_etau = 3
  
• we also removed the use of the wind speed (wndm array) in TKE and replaced it by the stress converted to speed. Wndm is keep in the code only for PISCES to compute gases exchanges at the surface of the free ocean or in the leads in sea-ice parts
  
• taum was added in iom outputs
  

[smasson]

done, see changeset:1705

[smasson]

rn_addhft can be positive or negative.
In any case, the MAX in

zdif = rn_sclhft * MAX( 0.e0, zdif + rn_addhft )

keep a positive value for zdif + rn_addhft

[anonymous]

Milestone 2009 Stream 0: Coupled Ready deleted