[MITgcm-support] External forcing for deltaT < 1 sec

[Jody Klymak]

On Apr 11, 2014, at  13:09 PM, Dustin Carroll <dcarroll at uoregon.edu> wrote:

> I tried using the basic periodicExternalForcing but that didn’t properly loop through my forcing files properly when deltaT < 1. Can anyone confirm that periodicExternalForcing works with deltaT < 1 or recommend a method for time dependent bc's with these small time steps?

Hi Dustin,

Not sure if I understand "didn't properly loop".  If deltaT>1. does it "properly loop"?  The source code you want to look at is get_periodic_interval.F, maybe that has a clue.

One thing to be careful about, which has got me in the past, is that your first record in your OBET_hr.bin etc is actually centered at 0.5*externForcingPeriod (=1800s), and that at t=0, the boundary condition is actually a linear interpolation between the records at -1800 s and at +1800 s i.e. between the *last* record in your file and the first.  If you are doing something with a linear initial ramp, and the last value you have in your hourly forcing is large, your t=0 startup will be a lot bumpier than you were hoping.

The justification for that convention is that a lot of folks force with monthly climatologies etc, which are most appropriately centered on the period.  

Cheers,  Jody