gradsf, gradsg

Given array z, compute its gradient via Spherepack.

Synopsis

    procedure gradsf(
        z   : float,
        gzx : float,
        gzy : float
    )

    procedure gradsg(
        z   : float,
        gzx : float,
        gzy : float
    )

Arguments

z: array to compute gradient of (input, two or more dimensions, last two dimensions must be nlat x nlon and input values must be in ascending latitude order).
gzx, gzy: gradient arrays (output, same dimensions as z, values will be in ascending latitude order)

Description

gradsf and gradsg both compute the gradient given the array z and return the results in the arrays gzy and gzy. gradsf operates on an equal (fixed) grid, and gradsg operates on a Gaussian grid.

Note: 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: 1.8 $ $Date: 1999/02/23 15:59:23 $