[MITgcm-support] Energy diagnostics?

[Jeffery Scott]

Hi Jody,

Several years ago Alistair and I worked out how to calculate this,  
i.e. ,  given complications due to Adams-Bashforth time stepping, and  
we able to diagnose under what conditions/run parameters the MITGCM  
conserves KE (albeit fairly limited testing of MITGCM options). PE is  
a bit more messy and I gave up at some point, perhaps others have had  
more patience.

However, we did this all offline, so I'm not sure how much help it  
would be, but happy to share, have some notes written up...

Jeff Scott


On Feb 16, 2009, at 3:51 AM, Martin Losch wrote:

> Hi Jody,
>
> I am not aware of energy flux diagnostics [(E+P)u] in the code. I  
> agree with you that for closing the budget they need to be computed  
> correctly (at each time step and then averaged), horizontal  
> averaging will also be an issue.
>
> Martin
>
> On Feb 15, 2009, at 10:25 PM, Klymak Jody wrote:
>
>>
>> Hi all,
>>
>> Before I spend a couple of days doing this, has anyone gone  
>> through the effort of calculating energy diagnostics?
>>
>> I'm running barotropic flow over an obstacle (all in 2-D).  If I  
>> take every timestep I can get a decent energy budget:
>>
>> (d/dt)\int E dV = \oint (E+P) u \cdot dA + \int \epsilon dV
>>
>> where \epsilon is specified and numerical dissipation.  However (E 
>> +P)u changes so much over my output timesteps the residual when  
>> compared w/ dE/dt is unrealistically large.      Averaging the  
>> linear and non-linear flux over the dump interval should give a  
>> much better estimate.
>>
>> Has anyone done this?  If not, I'll share my code.
>>
>> Thanks,  Jody
>>
>> --
>> Jody Klymak
>> http://web.uvic.ca/~jklymak/
>>
>>
>>
>>
>>
>>
>>
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