# 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)

### Reference Manual Control Panel

\$Revision: 1.8 \$ \$Date: 1999/02/23 15:59:26 \$