Version 14 (modified by gm, 10 years ago) (diff)

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Author : Gurvan Madec, Yevgeny Aksenov, Matthieu Leclair

ticket : #665

Branch : DEV_r1837_mass_heat_salt_fluxes


useful commands

* check out of NEMO directory:

svn co svn+ssh://gm@forge.ipsl.jussieu.fr/ipsl/forge/projets/nemo/svn/branches/DEV_r1837_mass_heat_salt_fluxes/NEMO

* commit :

svn ci  -m  "ticket:#665  blah_blah"    list_of_file


Description

Revisit the formulation of the fluxes between ocean, ice and atmosphere : an exchange of water (mass exchange) is now explicitly associated with an exchange of heat and salt content. This modification simplifies the implementation of a fully embedded sea-ice.

This update is the NOCS.4 task (Revisit of mass and salt fluxes) due by 2nd July 2010

The main modifications concern OPA, LIM2 and LIM3. They are:

(0) stylistic modification

style changes only have been put in revision 1855.

Nevertheless we have return back to the original revision 1850 from which we start from the trunk. The style changes we be re-added at the end of the development, after the testing phase.

The following is thus done directly from the trunk.

(1) heat content of Freezing/Melting? ice.

In both LIM2 and LIM3, the computation of the heat content of F/M ice is added.

LIM2 : the modules involved in the change are ….

  • ice_2.F90 : add arrays to describe the heat content associated with both snow and ice mass changes

We also change the name of the mass changes. Thus the following lines

   REAL(wp), PUBLIC, DIMENSION(jpi,jpj) ::   rdqsnif       !: Variation of snow mass 
   REAL(wp), PUBLIC, DIMENSION(jpi,jpj) ::   rdqicif       !: Variation of ice  mass 

becomes

   REAL(wp), PUBLIC, DIMENSION(jpi,jpj) ::   rdm_snw       !: Variation of snow mass over 1 time step           [Kg/m2]
   REAL(wp), PUBLIC, DIMENSION(jpi,jpj) ::   rdq_snw       !: heat content associated to rdm_snw                [J/m2]
   REAL(wp), PUBLIC, DIMENSION(jpi,jpj) ::   rdq_ice       !: Variation of ice  mass over 1 time step           [Kg/m2]
   REAL(wp), PUBLIC, DIMENSION(jpi,jpj) ::   rdq_ice       !: heat content associated to rdm_snw                [J/m2]
  • thd_ice_2.F90 : associated 1D array names (rdsnif_1d, rdmicif_1d) have been changed into (rdm_snw_1d, rdm_ice_1d) and (rdq_snw_1d, rdq_ice_1d) have been added.
  • limthd_2.F90 : introduce the new variable names, and pass the new variables (rdq_snw, rdq_ice) to the lim_thd_zdf and lim_thd_lac routines

Note 1: we suppress the change of sst_m from Celcius to Kelvin and vice versa by adding a " + rt0 " at the 2 places it is used.

Note 2: zfontn has been suppressed as the heat associated with the melting of solid precipitation is now added to qns in sbc modules (=⇒> TO BE DONE in SBC)

  • limthd_lac_2.F90 : introduce the new variable name (rdm_ice), and add the update of rdq_ice : the last DO loop of lim_thd_lac routine is transformed as follows :
          DO ji = kideb , kiut
             dvlbq_1d  (ji) = ( 1. - frld_1d(ji) ) * h_ice_1d(ji) - ( 1. - zfrl_old(ji) ) * zhice_old(ji)
             rdmicif_1d(ji) = rdmicif_1d(ji) + rhoic * dvlbq_1d(ji)
          END DO
    
    becomes
          DO ji = kideb , kiut
             dvlbq_1d  (ji) = ( 1. - frld_1d(ji) ) * h_ice_1d(ji) - ( 1. - zfrl_old(ji) ) * zhice_old(ji)
             rdm_ice_1d(ji) = rdm_ice_1d(ji) + rhoic * dvlbq_1d(ji)
             rdq_ice_1d(ji) = rdq_ice_1d(ji) + rcpic * dvlbq_1d(ji) * ( tfu_1d(ji) - rt0 )      ! heat content relative to rt0
          END DO
    
  • limthd_zdf_2.F90 : introduce the new variable names (rdm_snw, rdm_ice), and and add the computation/update of rdq_snw, rdq_ice :

§ " 9.1. Surface ablation and update of snow thickness and qstbif_1d ", the lines

          !--volume of snow lost after surface melting and the associated mass
          dvsbq_1d(ji) =  ( 1.0 - frld_1d(ji) ) * ( h_snow_1d(ji) - zhsnw_old(ji) - zsprecip(ji) )
          dvsbq_1d(ji) =  MIN( zzero , dvsbq_1d(ji) )
          rdmsnif_1d(ji) =  rhosn * dvsbq_1d(ji)

becomes

          !--volume of snow lost after surface melting and the associated mass
          dvsbq_1d(ji) =  ( 1.0 - frld_1d(ji) ) * ( h_snow_1d(ji) - zhsnw_old(ji) - zsprecip(ji) )
          dvsbq_1d(ji) =  MIN( zzero , dvsbq_1d(ji) )
          ztmp = rhosn * dvsbq_1d(ji)
          rdm_snw_1d(ji) =  ztmp
          !--heat content of the water provided to the ocean (referenced to rt0)
          rdq_snw_1d(ji) =  cpic * ztmp * ( rt0_snow - rt0 )

§ " 9.4. Case of total ablation (ice is gone but snow may be left) ", the lines :

          !---updating new ice thickness and computing the newly formed ice mass
          zhicnew   =  zihgnew * zhicnew
          rdmicif_1d(ji) =  rdmicif_1d(ji) + ( 1.0 - frld_1d(ji) ) * ( zhicnew - h_ice_1d(ji) ) * rhoic
          !---updating new snow thickness and computing the newly formed snow mass
          zhsnfi   = zhsn + zdhsnm
          h_snow_1d(ji) = MAX( zzero , zhsnfi )
          rdmsnif_1d(ji) =  rdmsnif_1d(ji) + ( 1.0 - frld_1d(ji) ) * ( h_snow_1d(ji) - zhsn ) * rhosn

becomes

          !---updating new ice thickness and computing the newly formed ice mass
          zhicnew   =  zihgnew * zhicnew
          ztmp    =  ( 1.0 - frld_1d(ji) ) * ( zhicnew - h_ice_1d(ji) ) * rhoic
          rdm_ice_1d(ji) =  rdm_ice_1d(ji) + ztmp
          !---heat content of the water provided to the ocean (referenced to rt0)
          ! use of rt0_ice is OK for melting ice, in case of freezing tfu_1d should be used. This is done in 9.5 section (see below)
          rdq_ice_1d(ji) =  cpic * ztmp * ( rt0_ice - rt0 )
          !---updating new snow thickness and computing the newly formed snow mass
          zhsnfi   = zhsn + zdhsnm
          h_snow_1d(ji) = MAX( zzero , zhsnfi )
          ztmp = ( 1.0 - frld_1d(ji) ) * ( h_snow_1d(ji) - zhsn ) * rhosn
          rdm_snw_1d(ji) = rdm_snw_1d(ji) + ztmp
          !---updating the heat content of the water provided to the ocean (referenced to rt0)
          rdq_snw_1d(ji) = rdq_snw_1d(ji) + cpic * ztmp * ( rt0_snow - rt0 )

§ " 9.5. Update internal temperature and ice thickness. ", the following lines have been added at the end :

          ! update the ice heat content given to the ocean in freezing case (part from rt0_ice to tfu_1d)
         ztmp = ( 1. - zidhb ) * rhoic * dvbbq_1d(ji)
         rdqicif_1d(ji) = rdqicif_1d(ji) + cpic * ztmp * ( tfu_1d(ji) - rt0_ice )

§ " 10. Surface accretion. ", the lines :

          !---  volume change of ice and snow (used for ocean-ice freshwater flux computation)
          rdmicif_1d(ji) = rdmicif_1d(ji) + ( 1.0 - frld_1d(ji) )   * ( zhicnew - h_ice_1d (ji) ) * rhoic
          rdmsnif_1d(ji) = rdmsnif_1d(ji) + ( 1.0 - frld_1d(ji) )   * ( zhsnnew - h_snow_1d(ji) ) * rhosn

becomes

          !---  volume change of ice and snow (used for ocean-ice freshwater flux computation)
          ztmp = ( 1.0 - frld_1d(ji) ) * ( zhicnew - h_ice_1d (ji) ) * rhoic
          rdm_ice_1d(ji) = rdm_ice_1d(ji) + ztmp
          rdq_ice_1d(ji) = rdq_ice_1d(ji) + cpic * ztmp * ( tfu_1d(ji) - rt0 )
!!gm BUG ??   snow ==>  only needed for nn_ice_embd == 0  (standard levitating sea-ice)
          ztmp = ( 1.0 - frld_1d(ji) )   * ( zhsnnew - h_snow_1d(ji) ) * rhosn
         rdm_snw_1d(ji) = rdm_snw_1d(ji) + ztmp
         rdq_snw_1d(ji) = rdq_snw_1d(ji) + cpic * ztmp * ( rt0_snow - rt0 )

and, at last, § " 11. Lateral ablation (Changes in sea/ice fraction) ", the lines :

          !--variation of ice volume and ice mass 
          dvlbq_1d(ji)   = zihic * ( zfrl_old(ji) - frld_1d(ji) ) * h_ice_1d(ji)
          rdmicif_1d(ji) = rdmicif_1d(ji) + dvlbq_1d(ji) * rhoic
          !--variation of snow volume and snow mass 
          zdvsnvol    = zihsn * ( zfrl_old(ji) - frld_1d(ji) ) * h_snow_1d(ji)
          rdmsnif_1d(ji) = rdmsnif_1d(ji) + zdvsnvol * rhosn

becomes

          !--variation of ice volume and ice mass 
          dvlbq_1d(ji)   = zihic * ( zfrl_old(ji) - frld_1d(ji) ) * h_ice_1d(ji)
          ztmp = dvlbq_1d(ji) * rhoic
          rdm_ice_1d(ji) = rdm_ice_1d(ji) + ztmp
!!gm
!!gm   This should be split in two parts:
!!gm         1-  heat required to bring sea-ice at tfu  : this part should be added to the heat flux taken from the ocean
!!gm                 cpic * ztmp * 0.5 * ( tbif_1d(ji,2) + tbif_1d(ji,3) - 2.* rt0_ice )
!!gm         2-  heat content of lateral ablation referenced to rt0 : this part only put in rdq_ice_1d
!!gm                 cpic * ztmp * ( rt0_ice - rt0 )
!!gm   Currently we put all the heat in rdq_ice_1d
          rdq_ice_1d(ji) = rdq_ice_1d(ji) + cpic * ztmp * 0.5 * ( tbif_1d(ji,2) + tbif_1d(ji,3) - 2.* rt0 )
          !
          !--variation of snow volume and snow mass 
          zdvsnvol = zihsn * ( zfrl_old(ji) - frld_1d(ji) ) * h_snow_1d(ji)
          ztmp     = zdvsnvol * rhosn
          rdm_snw_1d(ji) = rdm_snw_1d(ji) + ztmp
!!gm
!!gm   This should be split in two parts:
!!gm         1-  heat required to bring snow at tfu  : this part should be added to the heat flux taken from the ocean
!!gm                 cpic * ztmp * ( tbif_1d(ji,1) - rt0_snow )
!!gm         2-  heat content of lateral ablation referenced to rt0 : this part only put in rdqicif_1d
!!gm                 cpic * ztmp * ( rt0_snow - rt0 )
!!gm   Currently we put all the heat in rdqicif_1d
          rdq_snw_1d(ji) = rdq_snw_1d(ji) + cpic * ztmp * ( tbif_1d(ji,1) - rt0 )
  • phycst.F90 : style changes + :
     - update of name:    rau0r   ==>>  r1_rau0      ;      ro0cpr = r1_rau0_rcp
    
     - new variable:    xlsn = lfus * rhosn    (for lim3, already defined in lim2)  
                        lfus = xlsn / rhosn    (for lim2, already defined in lim3)
    

CAUTION : there is a need to homogenize the definition of constant for sea-ice at least between LIM-2 and LIM-3. This must be coordonated with CICE variables

LIM3 : the modules involved in the change are ….

(2) introduction of a explicit a salt flux

The emps field is suppress by introducing fsalt, the salt flux at the ocean surface (only non zero below sea-ice)

A symmetric name is chosen for the emp : fmass. Indeed emp is a mass flux expressed in Kg/m2/s. its name emp is miss leading: emp does not only represent the Evaporation minus Precipitation budget, as it also include the freezing or melting of sea-ice, and also sometime the runoff. Therefore using fmass appears more meaningful.

in case of linear free surface (no key_vvl defined), the salt flux take into account the concentration/dilution term

(3) Non-solar flux including the heat content of mass exchanges

the definition of qns is modified as follows: the non solar part of the surface heat flux takes now also into account the heat content changes due to the change in volume associated with evaporation, precipitation, ice freezing and ice melting.

(4) Update ocean and ice forcing

the modification of trasbc and limsbc modules in order to take into account the above changes (heat content of water exchanges and explicit salt flux)

N.B.

  • Philosophical change: in near future it appears that the use of key_vvl should be replaced by key_linssh. In other words, the defaut option of NEMO will be a non-linear free surface (and thus variable volume for the model levels). This has to be discussed prior to its implementation.

Testing

Testing could consider (where appropriate) other configurations in addition to NVTK].

NVTK Tested'''YES/NO'''
Other model configurations'''YES/NO'''
Processor configurations tested[ Enter processor configs tested here ]
If adding new functionality please confirm that the
New code doesn't change results when it is switched off
and ''works'' when switched on
'''YES/NO/NA'''

(Answering UNSURE is likely to generate further questions from reviewers.)

'Please add further summary details here'

  • Processor configurations tested
  • etc——

Bit Comparability

Does this change preserve answers in your tested standard configurations (to the last bit) ?'''YES/NO '''
Does this change bit compare across various processor configurations. (1xM, Nx1 and MxN are recommended)'''YES/NO'''
Is this change expected to preserve answers in all possible model configurations?'''YES/NO'''
Is this change expected to preserve all diagnostics?
,,''Preserving answers in model runs does not necessarily imply preserved diagnostics. ''
'''YES/NO'''

If you answered '''NO''' to any of the above, please provide further details:

  • Which routine(s) are causing the difference?
  • Why the changes are not protected by a logical switch or new section-version
  • What is needed to achieve regression with the previous model release (e.g. a regression branch, hand-edits etc). If this is not possible, explain why not.
  • What do you expect to see occur in the test harness jobs?
  • Which diagnostics have you altered and why have they changed?Please add details here……..

System Changes

Does your change alter namelists?'''YES/NO '''
Does your change require a change in compiler options?'''YES/NO '''

If any of these apply, please document the changes required here…….


Resources

''Please ''summarize'' any changes in runtime or memory use caused by this change……''


IPR issues

Has the code been wholly (100%) produced by NEMO developers staff working exclusively on NEMO?'''YES/ NO '''

If No:

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