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# uv2sfvpf

Computes the stream function and velocity potential via spherical harmonics given u and v on a fixed grid.

## Prototype

```	procedure uv2sfvpf (
u   : numeric,
v   : numeric,
sf  : float or double,
vp  : float or double
)
```

## Arguments

u
v

wind components (input, arrays with two or more dimensions, rightmost two dimensions must be nlat x nlon)

• input values must be in ascending latitude order
• input array must be on a global grid

sf

stream function (output, same dimensions as u and v, values will be in ascending latitude order)

vp

velocity potential (output, same dimensions as u and v, values will be in ascending latitude order)

## Description

Given wind components u and v, uv2sfvpf computes the stream function and the velocity potential and returns the results in the arrays sf and vp. uv2sfvpf operates on a fixed grid.

This procedure does not handle missing values (defined by the _FillValue attribute). If any missing values are encountered in a particular 2D input grid, then all of the values in the corresponding output grids will be set to the missing value defined by the output grids' _FillValue attributes.

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

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

If the input arrays u and v are on a gaussian grid, uv2sfvpg should be used. Also, note that uv2sfvpf is the procedural version of uv2sfvpF.

## Examples

Example 1

Compute the stream function and velocity potential, given the u and v wind components on a fixed grid.

```begin
nlat  =  73                                       ; dimensions
mlon  =  144
mlon1 = mlon+1
fbfile = "uv300.hs"

nrec  = fbinnumrec(fbfile)           ; total number of records in the file
ntim  = nrec/2                       ; number of time steps in dataset

uvmsg = 1e+36

sf    = new ( (/nlat,mlon /), float, uvmsg )  ; stream function
vp    = new ( (/nlat,mlon /), float, uvmsg )  ; velocity potential

do i = 0,nrec-1,2
month = 1                         ; January
if (i .ge. 2) then
month = 7                     ; July
end if

u    = work(:,0:mlon-1)
v    = work(:,0:mlon-1)

uv2sfvpf (u,v, sf,vp)             ; u,v ==> stream function + velocity pot
end do
end
```

## Errors

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 N (jer only)