[MITgcm-support] Re: rotate_spherical_polar_grid.F

[Martin Losch]

Hi Micheal,

I am replying via the support list, as this may be interesting to  
others:
I implemented the rotation so that you have to supply
1. the rotated coordiates via thetaMin,phiMin,dx/ySpacing, delX/Y, or  
files
2. the Euler angles that produce this rotated grid
rotate_spherical_polar_grid will then compute the real geographical  
coordinates (XC,YC,XG,YG) so that you can use the on-the-fly  
interpolation of the exf-package. These coordinates are then only  
used for computation of the coriolis force (and the interpolation of  
the exf-package).
As an example, this is what I do for a 1/4-degree grid with the  
equator rotated into the North Pole with the Euler angles (-30,-90,-90):
> &PARM04
> usingCartesianGrid=.FALSE.,
> usingSphericalPolarGrid=.TRUE.,
> #usingCurvilinearGrid = .TRUE.,
>  delR= ???
>  phiMin   = -20.75,
>  thetaMin = -20.75,
>  dxSpacing=0.25,
>  dySpacing=0.25,
>  phiEuler = -30.,
>  thetaEuler = -90.,
>  psiEuler = -90.,
>  &

Martin

PS. I admit that the name rotate_spherical_polar_grid is not a very  
good choice, it probably should have been called "rotate_back" or so.
PPS. the routine "calc_angles" which is in  
rotate_spherical_polar_grid.F could also be used to compute the angle  
between "grid-north" and geographical north for any grid, but it's  
not yet done.

On 1 Apr 2008, at 02:42, m. r. schaferkotter wrote:
> hi martin;
> i came across grid rotation capabilities when i updated recently.
>
> i/d like to take a  region domain that has axes along a latitude  
> and longitude and rotate the domain
> about it/s center point and run the model.
>
> i think i/ve got the Euler angles to do this.
>
> could you clarify the instructions in  rotate_spherical_polar_grid.F?
>
> do i supply the unrotated coordinates to the subroutine  
> rotate_spherical_polar_grid.F, by
> specifying thetaMin, phiMin, dx.bin, dy.bin?
>
> michael
>