From ht.fisher at protonmail.com  Thu Oct  2 13:03:56 2025
From: ht.fisher at protonmail.com (ht)
Date: Thu, 02 Oct 2025 17:03:56 +0000
Subject: [MITgcm-support] MITgcm-support Digest, Vol 267, Issue 7
In-Reply-To: <mailman.1.1758729601.31969.mitgcm-support@mitgcm.org>
References: <mailman.1.1758729601.31969.mitgcm-support@mitgcm.org>
Message-ID: <4wVV9dHnppCJxFfjt-iqe3MW5NzhJbDF6ovoFQHsEyu-jYE3yxCy6vl7q9CxqaWS2GqEOACbBWyQBTZ_DPbWBurvlMDc7NPZzETGrFri1R0=@protonmail.com>

Dear Jean-Michel,

Thank you very much for your detailed explanation?it is extremely helpful.

I understand now the distinction between aim_useFMsurfBC and aim_useMMsurfFc. Your clarification about which surface boundary-condition files are required (or replaced by prognostic variables) makes things much clearer.

Since in my case the SST input is a yearly averaged field with only a single record (constant in time), I will follow your suggestion as follows, so that the model will simply use the prescribed SST without repetition issues:
 &AIM_PARAMS
  aim_useFMsurfBC = .TRUE.,
  aim_useMMsurfFc = .FALSE.,
# aim_surfPotTemp = .TRUE.,
  aim_energPrecip = .TRUE.,
  aim_splitSIOsFx = .TRUE.,
  aim_LandFile   = 'landFrc.St36Ma_CLSD_CS32_revised.bin',
  aim_albFile    = 'Albedo.Ex10.bin',
# aim_vegFile    = '',
#
#  SST.Ex10.ocn_sym.bin: Original annual average SST data (shape: (32,192))
   aim_sstFile   = 'SST.Ex10.ocn_sym.bin',
# aim_lstFile    = '',
# aim_oiceFile   = '',
# aim_snowFile   = '',
# aim_swcFile    = '',
  aim_dragStrato = 2592000.,
  aim_clrSkyDiag = .TRUE.,
  aim_diagFreq   = 3110400000.,
  aim_select_pCO2 = 1,
  aim_fixed_pCO2  = 1000.E-6,
# atmpCO2init    = 800.E-6,
  aim_surfForc_NppCycle = 1,
 /

This really clarifies the setup I need?thank you again for taking the time to explain all these details.

I have one more question: instead of prescribing SST via data.aimphys (using aim_sstFile), would it also be valid to provide SST as a relaxation forcing in the data file, for example with:

 tauThetaClimRelax = 1.,
 thetaClimFile     = 'SST.Ex10.ocn_sym.bin',

Or is it preferable to always prescribe SST through data.aimphys?
(To be honest, I had previously run my simulation this way before your explanation.)

Best regards,
Fisher



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>  Today's Topics:
>  
>     1. Re: Questions on configuring AIM surface boundary conditions
>        (Jean-Michel Campin)
>  
>  
>  ----------------------------------------------------------------------
>  
>  Message: 1
>  Date: Tue, 23 Sep 2025 16:47:26 -0400
>  From: Jean-Michel Campin <jmc at mit.edu>
>  To: mitgcm-support at mitgcm.org
>  Subject: Re: [MITgcm-support] Questions on configuring AIM surface
>  	boundary conditions
>  Message-ID: <20250923204726.GA37914 at ocean.mit.edu>
>  Content-Type: text/plain; charset=us-ascii
>  
>  Hi Fisher,
>  
>  I will try to clarify few things:
>  > It seems that parameters like aim_useFMsurfBC and aim_useMMsurfFc control
>  > the use of boundary conditions, but I could not find detailed explanations
>  > for these flags. Could you clarify their meanings?
>  
>  The description (in AIM_PARAMS.h + repeated in STDOUT) is rather short:
>  C     aim_useFMsurfBC :: select surface B.C. from Franco Molteni
>  C     aim_useMMsurfFc :: select Monthly Mean surface forcing (e.g., NCEP)
>  These 2 logical parameters allows to select between a simplified monthly
>  mean forcing, that repeats itself over a year ( aim_useMMsurfFc=T, aim_useFMsurfBC=F)
>  and the original Speedy code (from Franco Molteni) surface forcing (aim_useFMsurfBC=T,
>  aim_useMMsurfFc=F, i.e., the default).
>  However, if you are using pkg/land (useLand=T, as in verification/aim.5l_cs/input/),
>  and assuming you don't turn off parts of the land code (keeping all 4 logical
>  parameters: land_calc_{grT,grW,snow,alb} set to True, i.e., the default),
>  many surface fields will be replaced by the land prognostics variables so that the
>  effective number of surface-BC fields to provide is reduced.
>  
>  And similarly, if you are using pkg/thsice (useThSIce=T, as in
>  verification/aim.5l_cs/input.thSI/), few more surface fields will be replaced
>  by pkg/thsice prognostics variables.
>  
>  > Also, should the boundary-condition data be provided as monthly values,
>  > or is another temporal format expected?
>  With aim_useMMsurfFc=T, monthly-mean values is the only option, with 1 file
>  per month (with 3 characters month suffix in the file name, see:
>  verification/aim.5l_LatLon/input settings).
>  
>  With aim_useFMsurfBC=T, all time records are in a single file. it still assumes
>  repeating forcing cycle, but since the repeating period is adjustable, if you provide
>  enough records to exceed the length of the simulation there will not be any repetition.
>  This is controlled by:
>  C     aim_surfForc_TimePeriod :: Length of forcing time period (e.g. 1 month)
>  C     aim_surfForc_NppCycle   :: Number of time period per Cycle (e.g. 12)
>  and the length of the repeating cycle is the product of the 2.
>  
>  To summarize, with aim_useFMsurfBC=T, the surface BC files you may provide are:
>   aim_LandFile : land fraction, loaded once (1 record) and kept fixed
>   aim_albFile  : surface albedo over land, loaded once (1 record) and kept fixed
>   aim_sstFile  : SST, multiple records
>  
>  Not used if useThSIce=T:
>   aim_oiceFile : seaice fraction, multiple records
>  
>  Not used if useLand=T:
>   aim_lstFile  : land surface Temp, multiple records
>   aim_swcFile  : soil water content, multiple records
>   aim_vegFile  : vegetation fraction, loaded once (1 record) and kept fixed
>   aim_snowFile: snow depth over land, multiple records
>  Note: some might still be used as Land default initial condition (at startTime=0,
>       myIter=nIter0=0), something I have not checked.
>  
>  Regarding this:
>  > If I want to prescribe only SST from data while letting the model internally
>  > compute albedo, land-surface temperature, Sea Ice fraction, and other variables,
>  > what is the correct way to set this up?
>  It seems to me that you will need both useLand=T and useThSIce=T (in data.pkg),
>  is this the case ?
>  And you still need to provide land-albedo (that will be modified where there
>  is snow).
>  
>  Finally, regarding the attached "data.aimphys", what is the type of time-variation
>  you are targeting for the SST ?
>  If it's constant, I will just change aim_useFMsurfBC=F to True and set:
>   aim_surfForc_NppCycle=1
>  (not the most efficient way but should do the job).
>  
>  Cheers,
>  Jean-Michel
>  
>  On Thu, Sep 18, 2025 at 01:14:17PM +0000, ht wrote:
>  > Dear Community,
>  >
>  > I am currently trying to set up atmospheric and land-surface simulations using MITgcm, taking MITgcm/verification/aim.5l_cs as a reference but with my own topography and SST distribution.
>  >
>  > I have several questions regarding the configuration files, especially data.aim:
>  >
>  > -
>  >
>  > It seems that parameters like aim_useFMsurfBC and aim_useMMsurfFc control the use of boundary conditions, but I could not find detailed explanations for these flags. Could you clarify their meanings? Also, should the boundary-condition data be provided as monthly values, or is another temporal format expected?
>  >
>  > -
>  >
>  > If I want to prescribe only SST from data while letting the model internally compute albedo, land-surface temperature, Sea Ice fraction, and other variables, what is the correct way to set this up?
>  >
>  > -
>  >
>  > I have attached my current data.aimphys file. Could you please check whether it is correctly configured for this purpose or if modifications are needed?
>  >
>  > Thank you very much for your time and support.
>  >
>  > Best regards,
>  > Fisher
>  
>  
>  > _______________________________________________
>  > MITgcm-support mailing list
>  > MITgcm-support at mitgcm.org
>  > http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support
>  
>  
>  
>  ------------------------------
>  
>  Subject: Digest Footer
>  
>  _______________________________________________
>  MITgcm-support mailing list
>  MITgcm-support at mitgcm.org
>  http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support
>  
>  
>  ------------------------------
>  
>  End of MITgcm-support Digest, Vol 267, Issue 7
>  **********************************************
>  

From jmc at mit.edu  Thu Oct  2 18:58:54 2025
From: jmc at mit.edu (Jean-Michel Campin)
Date: Thu, 2 Oct 2025 18:58:54 -0400
Subject: [MITgcm-support] MITgcm-support Digest, Vol 267, Issue 7
In-Reply-To: <4wVV9dHnppCJxFfjt-iqe3MW5NzhJbDF6ovoFQHsEyu-jYE3yxCy6vl7q9CxqaWS2GqEOACbBWyQBTZ_DPbWBurvlMDc7NPZzETGrFri1R0=@protonmail.com>
References: <mailman.1.1758729601.31969.mitgcm-support@mitgcm.org>
 <4wVV9dHnppCJxFfjt-iqe3MW5NzhJbDF6ovoFQHsEyu-jYE3yxCy6vl7q9CxqaWS2GqEOACbBWyQBTZ_DPbWBurvlMDc7NPZzETGrFri1R0=@protonmail.com>
Message-ID: <20251002225854.GA20663@ocean.mit.edu>

Hi Fisher,

Regarding this:
> I have one more question: instead of prescribing SST via data.aimphys (using aim_sstFile), 
> would it also be valid to provide SST as a relaxation forcing in the data file, 

This option exists but only with pkg/thsice (together with pkg/aim_v23), and it's
exactly what is done in verification/aim.5l_cs/input.thSI/ example:
  stepFwd_oceMxL=.TRUE.,  meaning SST is not imposed but evolves
and: tauRelax_MxL=5184000.,  is the SST relaxation time-scale toward pkg/aim_v23/ SST
i.e., the one you specify with:
>    aim_sstFile   = 'SST.Ex10.ocn_sym.bin',
 
Now I have to admit that this part (SST in pkg aim_v23 + thsice) is a little bit
convoluted (e.g., with the so called "Q-flux" file option is in "data.aimphys" as
well as the targeted SST file but the remaining parameters are in "data.ice"), and 
did not find any documentation about it.

And finally, these setting:
> for example with:
>  tauThetaClimRelax = 1.,
>  thetaClimFile     = 'SST.Ex10.ocn_sym.bin',
will not work as you expect, since it's only for Ocean GCM forcing.

Cheers,
Jean-Michel

On Thu, Oct 02, 2025 at 05:03:56PM +0000, ht wrote:
> Dear Jean-Michel,
> 
> Thank you very much for your detailed explanation???it is extremely helpful.
> 
> I understand now the distinction between aim_useFMsurfBC and aim_useMMsurfFc. Your clarification about which surface boundary-condition files are required (or replaced by prognostic variables) makes things much clearer.
> 
> Since in my case the SST input is a yearly averaged field with only a single record (constant in time), I will follow your suggestion as follows, so that the model will simply use the prescribed SST without repetition issues:
>  &AIM_PARAMS
>   aim_useFMsurfBC = .TRUE.,
>   aim_useMMsurfFc = .FALSE.,
> # aim_surfPotTemp = .TRUE.,
>   aim_energPrecip = .TRUE.,
>   aim_splitSIOsFx = .TRUE.,
>   aim_LandFile   = 'landFrc.St36Ma_CLSD_CS32_revised.bin',
>   aim_albFile    = 'Albedo.Ex10.bin',
> # aim_vegFile    = '',
> #
> #  SST.Ex10.ocn_sym.bin: Original annual average SST data (shape: (32,192))
>    aim_sstFile   = 'SST.Ex10.ocn_sym.bin',
> # aim_lstFile    = '',
> # aim_oiceFile   = '',
> # aim_snowFile   = '',
> # aim_swcFile    = '',
>   aim_dragStrato = 2592000.,
>   aim_clrSkyDiag = .TRUE.,
>   aim_diagFreq   = 3110400000.,
>   aim_select_pCO2 = 1,
>   aim_fixed_pCO2  = 1000.E-6,
> # atmpCO2init    = 800.E-6,
>   aim_surfForc_NppCycle = 1,
>  /
> 
> This really clarifies the setup I need???thank you again for taking the time to explain all these details.
> 
> I have one more question: instead of prescribing SST via data.aimphys (using aim_sstFile), would it also be valid to provide SST as a relaxation forcing in the data file, for example with:
> 
>  tauThetaClimRelax = 1.,
>  thetaClimFile     = 'SST.Ex10.ocn_sym.bin',
> 
> Or is it preferable to always prescribe SST through data.aimphys?
> (To be honest, I had previously run my simulation this way before your explanation.)
> 
> Best regards,
> Fisher
> 
> 
> 
> >  Send MITgcm-support mailing list submissions to
> >  	mitgcm-support at mitgcm.org
> >  
> >  To subscribe or unsubscribe via the World Wide Web, visit
> >  	http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support
> >  or, via email, send a message with subject or body 'help' to
> >  	mitgcm-support-request at mitgcm.org
> >  
> >  You can reach the person managing the list at
> >  	mitgcm-support-owner at mitgcm.org
> >  
> >  When replying, please edit your Subject line so it is more specific
> >  than "Re: Contents of MITgcm-support digest..."
> >  
> >  
> >  Today's Topics:
> >  
> >     1. Re: Questions on configuring AIM surface boundary conditions
> >        (Jean-Michel Campin)
> >  
> >  
> >  ----------------------------------------------------------------------
> >  
> >  Message: 1
> >  Date: Tue, 23 Sep 2025 16:47:26 -0400
> >  From: Jean-Michel Campin <jmc at mit.edu>
> >  To: mitgcm-support at mitgcm.org
> >  Subject: Re: [MITgcm-support] Questions on configuring AIM surface
> >  	boundary conditions
> >  Message-ID: <20250923204726.GA37914 at ocean.mit.edu>
> >  Content-Type: text/plain; charset=us-ascii
> >  
> >  Hi Fisher,
> >  
> >  I will try to clarify few things:
> >  > It seems that parameters like aim_useFMsurfBC and aim_useMMsurfFc control
> >  > the use of boundary conditions, but I could not find detailed explanations
> >  > for these flags. Could you clarify their meanings?
> >  
> >  The description (in AIM_PARAMS.h + repeated in STDOUT) is rather short:
> >  C     aim_useFMsurfBC :: select surface B.C. from Franco Molteni
> >  C     aim_useMMsurfFc :: select Monthly Mean surface forcing (e.g., NCEP)
> >  These 2 logical parameters allows to select between a simplified monthly
> >  mean forcing, that repeats itself over a year ( aim_useMMsurfFc=T, aim_useFMsurfBC=F)
> >  and the original Speedy code (from Franco Molteni) surface forcing (aim_useFMsurfBC=T,
> >  aim_useMMsurfFc=F, i.e., the default).
> >  However, if you are using pkg/land (useLand=T, as in verification/aim.5l_cs/input/),
> >  and assuming you don't turn off parts of the land code (keeping all 4 logical
> >  parameters: land_calc_{grT,grW,snow,alb} set to True, i.e., the default),
> >  many surface fields will be replaced by the land prognostics variables so that the
> >  effective number of surface-BC fields to provide is reduced.
> >  
> >  And similarly, if you are using pkg/thsice (useThSIce=T, as in
> >  verification/aim.5l_cs/input.thSI/), few more surface fields will be replaced
> >  by pkg/thsice prognostics variables.
> >  
> >  > Also, should the boundary-condition data be provided as monthly values,
> >  > or is another temporal format expected?
> >  With aim_useMMsurfFc=T, monthly-mean values is the only option, with 1 file
> >  per month (with 3 characters month suffix in the file name, see:
> >  verification/aim.5l_LatLon/input settings).
> >  
> >  With aim_useFMsurfBC=T, all time records are in a single file. it still assumes
> >  repeating forcing cycle, but since the repeating period is adjustable, if you provide
> >  enough records to exceed the length of the simulation there will not be any repetition.
> >  This is controlled by:
> >  C     aim_surfForc_TimePeriod :: Length of forcing time period (e.g. 1 month)
> >  C     aim_surfForc_NppCycle   :: Number of time period per Cycle (e.g. 12)
> >  and the length of the repeating cycle is the product of the 2.
> >  
> >  To summarize, with aim_useFMsurfBC=T, the surface BC files you may provide are:
> >   aim_LandFile : land fraction, loaded once (1 record) and kept fixed
> >   aim_albFile  : surface albedo over land, loaded once (1 record) and kept fixed
> >   aim_sstFile  : SST, multiple records
> >  
> >  Not used if useThSIce=T:
> >   aim_oiceFile : seaice fraction, multiple records
> >  
> >  Not used if useLand=T:
> >   aim_lstFile  : land surface Temp, multiple records
> >   aim_swcFile  : soil water content, multiple records
> >   aim_vegFile  : vegetation fraction, loaded once (1 record) and kept fixed
> >   aim_snowFile: snow depth over land, multiple records
> >  Note: some might still be used as Land default initial condition (at startTime=0,
> >       myIter=nIter0=0), something I have not checked.
> >  
> >  Regarding this:
> >  > If I want to prescribe only SST from data while letting the model internally
> >  > compute albedo, land-surface temperature, Sea Ice fraction, and other variables,
> >  > what is the correct way to set this up?
> >  It seems to me that you will need both useLand=T and useThSIce=T (in data.pkg),
> >  is this the case ?
> >  And you still need to provide land-albedo (that will be modified where there
> >  is snow).
> >  
> >  Finally, regarding the attached "data.aimphys", what is the type of time-variation
> >  you are targeting for the SST ?
> >  If it's constant, I will just change aim_useFMsurfBC=F to True and set:
> >   aim_surfForc_NppCycle=1
> >  (not the most efficient way but should do the job).
> >  
> >  Cheers,
> >  Jean-Michel
> >  
> >  On Thu, Sep 18, 2025 at 01:14:17PM +0000, ht wrote:
> >  > Dear Community,
> >  >
> >  > I am currently trying to set up atmospheric and land-surface simulations using MITgcm, taking MITgcm/verification/aim.5l_cs as a reference but with my own topography and SST distribution.
> >  >
> >  > I have several questions regarding the configuration files, especially data.aim:
> >  >
> >  > -
> >  >
> >  > It seems that parameters like aim_useFMsurfBC and aim_useMMsurfFc control the use of boundary conditions, but I could not find detailed explanations for these flags. Could you clarify their meanings? Also, should the boundary-condition data be provided as monthly values, or is another temporal format expected?
> >  >
> >  > -
> >  >
> >  > If I want to prescribe only SST from data while letting the model internally compute albedo, land-surface temperature, Sea Ice fraction, and other variables, what is the correct way to set this up?
> >  >
> >  > -
> >  >
> >  > I have attached my current data.aimphys file. Could you please check whether it is correctly configured for this purpose or if modifications are needed?
> >  >
> >  > Thank you very much for your time and support.
> >  >
> >  > Best regards,
> >  > Fisher
> >  
> >  
> >  > _______________________________________________
> >  > MITgcm-support mailing list
> >  > MITgcm-support at mitgcm.org
> >  > http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support
> >  
> >  
> >  
> >  ------------------------------
> >  
> >  Subject: Digest Footer
> >  
> >  _______________________________________________
> >  MITgcm-support mailing list
> >  MITgcm-support at mitgcm.org
> >  http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support
> >  
> >  
> >  ------------------------------
> >  
> >  End of MITgcm-support Digest, Vol 267, Issue 7
> >  **********************************************
> >  
> _______________________________________________
> MITgcm-support mailing list
> MITgcm-support at mitgcm.org
> http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support