Interpolates a scalar quantity from one Gaussian grid to another (with optional truncation).
function g2gsh ( grid : numeric, outdims  : byte, short, integer or long, twave  : integer ) return_val : float or double
An array of 2 or more dimensions whose rightmost two dimensions must be latitude x longitude. The values must be in ascending latitude order.outdims
An array indicating the dimensions of the rightmost two dimensions of the output grid (outdims = nlatb, outdims = nlonb).
As of version 6.0.0, this can be of type byte, short, integer or long.twave
A scalar integer indicating the optional wave truncation:
twave = 0 => exact interpolation
twave > 0 => exact interpolation and triangular truncation at twave
twave < 0 => exact interpolation, triangular truncation at twave and spectral coefficient tapering (the effect is to smooth the data)
The return array's dimensions are the same as grid's dimensions, except the rightmost two dimensions, nlata and nlona, are replaced by nlatb and nlonb. The type will be double if the input is double, and float otherwise.
If missing values are encountered in a 2D subsection of the input array, then no interpolation will be performed on that 2D array, and the corresponding 2D subsection of the return array will be filled with missing values.
Arrays which have dimensions [...] x nlata x nlona should not include the cyclic (wrap-around) points when invoking this function. For example, if an array x has dimensions nlata = 64 and nlona = 129, where the "129" represents the cyclic point, then the user should pass the data to g2gsh via:
z = g2gsh ( x(...,0:nlona-2), twave ) ; does not include cyclic points
This function can only be used on grids that span the globe. It cannot be used for limited area grids.
Please read the caveats that you should be aware of when using spherical harmonic regridding.
Use g2gsh_Wrap if retention of metadata is desired.
Assume x is dimensioned nt x nlat x nlon. The code below interpolates from a Gaussian T63 grid (nlat=96,nlon=192) to a Gaussian T42 grid (jlat=64,ilon=128) with triangular truncation at wave 42:
X = g2gsh (x, (/jlat,ilon/), 42) ; ==> X(nt,jlat,ilon)
ier is equal to:
4 or 10 if nlona is less than 4
5 or 10 if nlata is less than 3
8 if nlonb is less than 4
9 if nlatb is less than 3