[MITgcm-support] tendency of kinetic energy diagnostics

[Baylor Fox-Kemper]

Hi XXXXX,
   What you will need to form energy budgets are terms from the  
models' momentum and buoyancy equations.  Almost all of the terms in  
those equations can be diagnosed just by using the diagnostics  
package and changing data.diagnostics to save them in time-mean or  
snapshots.  Once you've got the results of those equations, you can  
just multiply together the terms to get the terms you want in the  
energy equation.
   In fact, kinetic energy itself is one of those diagnostics, so if  
you are really only interested in the rate of change of KE, you can  
just dump KE at different snapshots and take differences.
   Or, if you can just run the model, you can calculate KE at every  
point just like the model does (using matlab or whatever).  The  
model's code for KE is given in

pkg/mom_common/mom_calc_ke.F

Roughly, the vector invariant form of the model uses

KE= 1/2( <U^2>_i+<V^2>_j)

Where angle brackets denote averaging in the horizontal in the i (x- 
direction) and j so that U and V will be co-located in space.

If you are using the fluxform form of the model, you've got a little  
more work to do, since the averaging is weighted by the areas of each  
gridpoint.  In that case, go check out the code.

Good luck,
    -Baylor

On Nov 29, 2006, at 1:10 PM, Yuan Lian wrote:

> Hi, XXXXX,
>
> One way you can diagnose the tendency of the kinetic energy is  
> programming with Matlab. Here are some nice references for how to  
> calculate it:
>
> "Physics of Climate" (book) by Peixoto and Oort, page 375-379, 1991.
> "Available potential energy and the maintenance of the general  
> circulation" by Lorenz, Tellus, 7, page 157-167, 1955.
>
> The programming is pretty straight forward based on the equations  
> provided by the references above.
>
> Yuan
>
>
> XXXXX XXXXX wrote:
>
>>> Hi,
>>> My name is XXXXX XXXXX, and I am a PhD student in Oceanography   
>>> from Stockholm University. I'm using the mitgcm, and are trying  
>>> to  diagnose the rate of change/tendency of kinetic energy. I've  
>>> red  parts of the manual about defining youre own diagnostics.  
>>> I'm  really a rookie when it comes to programming
>>>
>>> What would be the easiest way?
>>>
>>> D W
>>>
>>> XXXXX
>>>
>>
>> --------------------------------------------------------------------- 
>> ---
>>
>> _______________________________________________
>> MITgcm-support mailing list
>> MITgcm-support at mitgcm.org
>> http://mitgcm.org/mailman/listinfo/mitgcm-support
>>
>
> _______________________________________________
> MITgcm-support mailing list
> MITgcm-support at mitgcm.org
> http://mitgcm.org/mailman/listinfo/mitgcm-support