[MITgcm-support] temperature tendency equation

[David Wang]

Hi Andrea,

I do use diagnostics pkg and dump out the diagnostics quantities that 
you listed below. However there is no pre-defined diagnostics for the 
term (theta * volume divergence) that I mentioned, so I may have to, as 
you suggested, define a user-defined diagnostics for it. But to get 
quicker results, now I use rigid-lid surface instead, so that term 
vanishes at the surface layer as it does at all subsurface layers.

Thanks, David

Andrea Molod wrote:

> hi d.w.,
>
> On Tue, 6 Dec 2005, dwang at ldeo.columbia.edu wrote:
>
>> I'd like to diagnose every term of temperature tendency equation 
>> averaged over a
>> period of time, say 10 days. There is a term which only applies to 
>> the surface
>> layer (I use linear implicit free-surface): theta * div(velocity 
>> vector), in
>> gad_calc_rhs.F it has the form like:
>>
>> This term is "nonlinear" in the sense that it's a product. It seems 
>> that I have
>> to save T/U/V/W at every tracer timestep in order to estimate its 
>> time average
>> (is this the correct way?). My question is, is there any better 
>> approach?
>
>
> i don't know if you are using the diagnostics package or not, but it 
> seems to me the most reasonable solution to what you want to do. you 
> can read about how to use it in the MITgcm online documentation. there 
> are also at least a few verification experiments that use it, so you 
> can look there to find concrete examples. there are a set of 
> diagnostics that are pre-set for the temp. tend eqn, they are:
>
>   'ADVr_TH' | K.Pa.m^2/s   | Vertical   Advective Flux of Pot.Temperature
>   'ADVx_TH' | K.Pa.m^2/s   | Zonal      Advective Flux of Pot.Temperature
>   'ADVy_TH' | K.Pa.m^2/s   | Meridional Advective Flux of Pot.Temperature
>   'DFrE_TH' | K.Pa.m^2/s   | Vertical Diffusive Flux of 
> Pot.Temperature (Explicit part)
>   'DIFx_TH' | K.Pa.m^2/s   | Zonal      Diffusive Flux of Pot.Temperature
>   'DIFy_TH' | K.Pa.m^2/s   | Meridional Diffusive Flux of Pot.Temperature
>   'DFrI_TH' | K.Pa.m^2/s   | Vertical Diffusive Flux of 
> Pot.Temperature (Implicit part)
>
> to use these, just 'enable them' in the data.diagnostics namelist, and 
> include the DIAGNOSTICS_SIZE.h (with the approriate settings in there) 
> in your code directory. then all that needs to be saved is the time 
> average of the tendency terms.
>
> if these are not adequate, you can take advantage of the 
> 'user-defined' diagnostic options that are built in. this entails 
> 'enabling' a set of diagnostics called, eg, 'UDIAG1' (as any other 
> diagnostic is enabled), and then adding a single subroutine call to 
> the appropriate routine to fill the diagnostic with whatever 
> combination of terms you want.
>
> have fun!
>
> andrea molod
>
-- 

Daiwei (David) Wang    Graduate Student
Lamont-Doherty Earth Observatory of Columbia University
103B Oceanography
61 Route 9W, Palisades, NY 10964-8000
Voice: (845) 365-8694