[MITgcm-support] [EXTERNAL] forcing model with hflux and sflux

Fri Apr 8 07:33:12 EDT 2022

Hi Rita,

if you do this, you should keep in mind that before the sea ice model is called, Qnet = Qnet_ocean = lwdown + remaining terms.
After the sea ice model has been called Qnet = Qnet_ocean*(1-AREA) + Qnet_ice*AREA (Area = seaice fractional area \elem [0,1]), and lwdown is not used anymore.
If you don’t care about the sea ice model, you could add any heat anomaly dQ to Qnet **after** calling the sea ice model (in do_oceanic_phys), but this will likely change the surface temperature so that is inconsistent with the sea ice model.
If you add your anomaly before calling the sea ice model (ie. somewhere to the fields of the exf pkg), this would be similar as adding these heat anomalies like this: Qnet + dQ*(1-AREA), after the seaice, i.e only over the open ocean part (except that you dQ affects the sea ice model, too). So I’d add dQ*(1-AREA) to Qnet after calling the sea ice model to be on the safe side.

Martin

> On 8. Apr 2022, at 12:37, Margarita Markina <margarita.markina at earth.ox.ac.uk> wrote:
> 
> Thanks again Dimitris and Martin - all suggestions are very useful!
> 
> Since my aim is to investigate oceanic response to perturbations in heat flux that we want to apply in certain locations - we were thinking that another way to do it (without turning off ice model so we have all ice feedbacks) - would be to stick with using bulk formulae - but add desired localized anomalies to downward longwave radiation flux? since the Qnet is anyways a sum of DLW, DSW and latent and sensible heat fluxes. Do you think it could be a viable option?
> 
> 
> Thanks again, 
> Rita
> From: MITgcm-support <mitgcm-support-bounces at mitgcm.org <mailto:mitgcm-support-bounces at mitgcm.org>> on behalf of Menemenlis, Dimitris (US 329B) <dimitris.menemenlis at jpl.nasa.gov <mailto:dimitris.menemenlis at jpl.nasa.gov>>
> Sent: Thursday, April 7, 2022 6:46 PM
> To: MITgcm Support <mitgcm-support at mitgcm.org <mailto:mitgcm-support at mitgcm.org>>
> Subject: Re: [MITgcm-support] [EXTERNAL] forcing model with hflux and sflux
>  
> Hi Rita, although hflux and sflux are not compatible with pkg/seaice or pkg/thsice, there is a super-simple MITgcm sea ice model that is:
> 
> You enable it with option “allowFreezing=.TRUE.” under namelist PARM01 in runtime parameter file “data"
> 
> C     allowFreezing  :: Allows surface water to freeze and form ice
> 
> C     adjustColdSST_diag :: diagnostic field for how much too cold (below
> C              Tfreezing) SST has been adjusted (with allowFreezing=T).
> C              > 0 for increase of SST (up to Tfreezing).
> C              Units are r_unit.K/s (=Kelvin.m/s if r=z).
> C        Note: 1) allowFreezing option is a crude hack to fix too cold SST that
> C              results from missing seaice component. It should never be used
> C              with any seaice component, neither current seaice pkg (pkg/seaice
> C              or pkg/thsice) nor a seaice component from atmos model when
> C              coupled to it.
> 
> 
>> On Apr 5, 2022, at 3:17 AM, Martin Losch <Martin.Losch at awi.de <mailto:Martin.Losch at awi.de>> wrote:
>> 
>> Hi Rita,
>> 
>> the code cannot apply hflux/sflux with the sea ice model turned on, because the sea ice model computes these fluxes where there is ice. Frankly, what do you need the sea ice model for, if you want to prescribe the fluxes anyway? In this sense I’d support Dimitris’ suggestion. The fluxes that you prescribe should know about the sea ice distribution. It’s like prescribing the sea ice cover. If you want to have the sea ice modify these fluxes, more work is needed (and it will be complicated to get it “right”, i.e. consistent).
>> 
>> You’ll have to find a solution where you allow the model to compute the fluxes (from atmospheric fields that it reads) **and** read them. Depending what you want to do exactly I would have a look at pkg/exf and pkg/seaice and comment out the stop statements that bother you. Then you’d have to prescribe both the fluxes and the atmospheric fields and modify the code so that the fluxes are not overwritten by the ones that the exf-package computes. The sea ice model will then use the atmospheric fluxes (which you have prescribed) and recompute them in grid cells with sea ice. That could work, but I have never tried it.
>> 
>> Martin
>> 
>>> On 5. Apr 2022, at 12:03, Margarita Markina <margarita.markina at earth.ox.ac.uk <mailto:margarita.markina at earth.ox.ac.uk>> wrote:
>>> 
>>> It is subpolar latitudes, so I need the sea ice unfortunately 🙁
>>> 
>>> is there a way to force the model with hflux/sflux when sea ice module is on?
>>> 
>>> Or alternatively (if the former is impossible) - is there a way to add some fixed values (in certain locations) to heat fluxes computed within the model? 
>>> 
>>> 
>>> All the best, 
>>> Rita
>>> From: MITgcm-support <mitgcm-support-bounces at mitgcm.org <mailto:mitgcm-support-bounces at mitgcm.org>> on behalf of Menemenlis, Dimitris (US 329B) <dimitris.menemenlis at jpl.nasa.gov <mailto:dimitris.menemenlis at jpl.nasa.gov>>
>>> Sent: Tuesday, April 5, 2022 10:49 AM
>>> To: mitgcm-support at mitgcm.org <mailto:mitgcm-support at mitgcm.org> <mitgcm-support at mitgcm.org <mailto:mitgcm-support at mitgcm.org>>
>>> Subject: Re: [MITgcm-support] [EXTERNAL] forcing model with hflux and sflux
>>>  
>>> Turn off the sea ice module ;-)
>>> 
>>> > On Apr 5, 2022, at 2:43 AM, Margarita Markina <margarita.markina at earth.ox.ac.uk <mailto:margarita.markina at earth.ox.ac.uk>> wrote:
>>> > 
>>> > So, my question is -  how do I set my model so it is forced by hflux and sflux without getting errors from sea ice module?
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