[ecco-support] [EXTERNAL] Momentum Budget Terms

[Helen R Pillar]

Hi Deb & Ian,

Thanks Patrick for sharing our doc - I hope it is helpful. To summarize, we could close the momentum budget in ASTE with existing diagnostics and the addition of 2 new diagnostics to compute acceleration from (1) the surface PGF and (2) the implicit viscosity online (see eqs 20 & 21). 

I never got the surface PGF correct when I tried to compute it offline from ETAN, so we write a new diagnostic (our [U,V]m_dPsd[x,y]) from the momentum_correction_step S/R. Since ECCOv4 uses non-linear free surface with real freshwater flux and z* coordinates I think you will also need to compute the implicit viscosity online (our [U,V]m_Impl). If you use linear free surface you can compute it offline from VISrI_[U,V]m as described in the doc. 

So I think you will need both of these diagnostics to close the budget in ECCOv4, but others on this list may know better ; ) 

Our code modifications and data.diagnostics can be pulled from TACC (See section 7). 

Please let me know if I can help or provide further clarification.

Best wishes,

Helen


> On 6 Jul 2021, at 17:24, Patrick Heimbach <heimbach at mit.edu> wrote:
> 
> Hi there,
> 
> Helen Pillar (cc-ed) recently wrote a memo on how to close the momentum budget, please see
> https://hdl.handle.net/1721.1/130943
> 
> It has been tested for ASTE, but should be close to ECCOv4 (so perhaps 1/2 bonus point ;)
> 
> Best,
> Patrick
> 
> 
>> On Jul 6, 2021, at 7:06 PM, Fenty, Ian G (US 329C) <ian.fenty at jpl.nasa.gov> wrote:
>> 
>> Hi Deb,
>> Good question.  The vorticity budget tutorial (made by Maike Julie, https://github.com/maikejulie/) uses a number of fields that we have not traditionally included as part of the official solution and so they are not on the ECCO drive.  
>> 
>> Looking at the vorticity budget tutorial I found the following set of variables:
>> 
>>    PHI_SURF      ETAN          Vm_Advec      Vm_Cori  
>>    AB_gV         Vm_dPHdy      Vm_Ext        TOTVTEND 
>>    VISrI_Vm      VBotDrag      Vm_Diss       AB_gU    
>>    VISrI_Um      Um_dPHdx      Um_Ext        Um_Diss       
>>    TOTUTEND      UBotDrag      Um_Cori       Um_Advec 
>> 
>> Of these we only include Um_dPHdx, Vm_dPHdy, ETAN, and PHI_SURF (via PHI_HYD). 
>> 
>> We could re-run V4r4 to generate the fields needed to close the momentum budget and add those fields for our future releases.  Can you confirm exactly which fields are needed?  Matt Mazloff (cc’d) may be able to help.
>> 
>> -Ian Fenty
>> 
>> 
>> On 7/6/21, 4:10 PM, "ecco-support-bounces at mit.edu on behalf of Deborah Gardner" <ecco-support-bounces at mit.edu on behalf of dagardne at ucsd.edu> wrote:
>> 
>> Hi all,
>> 
>> I'm looking for the Um_[variable] terms and can't locate them in the ECCO drive. I'm looking to diagnose a closed momentum budget which I believe can only be accomplished with specific variables as opposed to computing with velocity variables. Does anyone know where I might be able to find the variables used in the Vorticity Budget Tutorial? Bonus points if it's Release 4
>> 
>> 
>> Deb Gardner (she/her/ella)
>> Best Waffle Topping, 2019 | Scripps Institution of Oceanography
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