# lderuvf, lderuvg

Given vector function (u,v), compute the latitudinal derivatives
(uy,vy) via Spherepack.

## Synopsis

procedure lderuvf(
u : float,
v : float,
uy : float,
vy : float
)
procedure lderuvg(
u : float,
v : float,
uy : float,
vy : float
)

## Arguments

*u, v*
- vector function arrays (input, two or more dimensions, last two
dimensions must be
*nlat* x *nlon* and input values must be
in ascending latitude order)
*uy, vy*
- vector latitudinal derivative arrays (output, same dimensions as
*u, v*, values will be in ascending latitude order)

## Description

*lderuvf* and *lderuvg* both compute the latitudinal
derivative vector arrays from the vector function *u* and
*v* and return the results in the arrays *uy* and
*vy*. *lderuvf* operates on an equal (fixed) grid, and
*lderuvg* 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 15:59:26 $ *