shaec, shagc

Procedures for computing spherical harmonic analyses via Spherepack.

Synopsis

    procedure shaec(
        g : float,
        a : float,
        b : float
    )

    procedure shagc(
        g : float,
        a : float,
        b : float
    )

Arguments

g
discrete function to be analyzed (input, array with two or more dimensions, last two dimensions must be nlat x nlon and values must be in ascending latitude order, but see note below)
a, b
spherical harmonic coefficients (input/output, same dimensions as g, except last two dimensions must be nlat x nlat and values must/will be in ascending latitude order, but see note below)

Description

Note: If you have version 4.1 of NCL, these procedures will not work with arrays greater than two dimensions. In order to use arrays with more than two dimensions, you need to run version 4.1.1 of NCL. If your site is licensed for version 4.1, then you can get version 4.1.1 for free. To get version 4.1.1 of NCAR Graphics software, please contact your site representative. If you don't know who your site representative is, then send email to ncarginf@ucar.edu or call (303) 497-1201.

shaec and shagc both perform the spherical harmonic analysis on the array g and store the results in the arrays a and b. shaec operates on an equal (fixed) grid, and shagc operates on a Gaussian grid.

For the arrays whose last two dimensions are nlat x nlon, the rest of the dimensions (if any) are collectively referred to as nt. If the input/output arrays are just two dimensions, then nt can either be considered equal to 1 or nothing at all.

Arrays which have dimensions nt x nlat x nlon should not include the cyclic (wraparound) points when invoking the procedures and functions which use spherical harmonics (Spherepack).

For example, if an array x has dimensions nlat = 64 and nlon = 129, where the "129" represents the cyclic points, then the user should pass the data to the procedure/function via: 

    z = sample ( x([...],:,0:nlon-2) )  ; does not include cyclic points

Error messages

If jer or ker is equal to:
1 : error in the specification of nlat
2 : error in the specification of nlon
4 : error in the specification of nt (jer only)

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$Revision: 1.12 $ $Date: 1999/04/29 21:32:20 $