[MITgcm-support] questions re. external forcing

[David Wang]

Hi Holly,

Concerning flux balancing. There could be better solutions. But what I did
is to go back to the model input files, calculate the annual-, global
(global in terms of your entire model domain) mean and subtract this number
(hopefully not a large one) from the original flux at every grid point. Then
feed the model with the "balanced" flux input data. This preserves the
seasonal cycle.

HTH,
D.

On Thu, Mar 26, 2009 at 7:17 PM, Holly Dail <hdail at mit.edu> wrote:

> Hello -
>
> I have a couple of questions regarding external forcing and would be most
> grateful for advice.  For background, my model setup is:
> - 1 degree isotropic N. Atlantic with closed boundaries near 20 S and 70 N
> (well, closed for now anyway)
> - external forcing with NCEP fields & bulk formula
> - interested in quasi steady-state behavior over hundreds of years (e.g.
> tracer distributions)
> - I want to include seasons, but plan to neglect (for the moment)
> inter-annual variability
>
> On to the questions:
> - I'd like to use the model calendar for my simulation / output, and
> Gregorian for the EXF fields.  When one sets  TheCalendar='model' in
> data.cal, what does the model assume about the calendar for the fields
> defined in data.exf?  Are 365 days/year fields interpolated to 360 days, or
> do the seasons 'move' by 5 days/year of simulation due to calendar
> mis-match?
>
> - I'd like to have balanced net heat and freshwater fluxes on an annual
> basis to hopefully reach a quasi steady-state.   I tried adding #define
> ALLOW_BALANCE_FLUXES in CPP_OPTIONS.h and balanceQnet=.TRUE.,
> balanceEmPmR=.TRUE. in data.  This works great, but I believe sets the net
> fluxes to zero in each time step.  This is problematic for seasonality.
> Since evaporation is computed on the fly, I am also limited in what I can do
> in 'correcting' heat flux and freshwater fields before the run.
> In the absence of other options, I'm thinking of modifying the code to
> compute the net heat flux and FW flux accumulated over a year and use it to
> 'correct' the following year's fluxes.    Are there better / cleaner ways to
> do this?
>
> Thanks for any help!
> Holly
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