f2fshv, f2gshv, g2fshv, g2gshv, f2foshv, fo2fshv

Grid-to-grid procedures for vector quantities using Spherepack routines.

Synopsis

```    procedure f2fshv(
ua    : float,
va    : float,
ub    : float,
vb    : float
)

procedure g2fshv(
ua    : float,
va    : float,
ub    : float,
vb    : float
)

procedure f2gshv(
ua    : float,
va    : float,
ub    : float,
vb    : float,
twave[1] : integer
)

procedure g2gshv(
ua    : float,
va    : float,
ub    : float,
vb    : float,
twave[1] : integer
)

procedure fo2fshv(
uoff  : float,
voff  : float,
ureg  : float,
vreg  : float
)

procedure f2foshv(
ureg  : float,
vreg  : float,
uoff  : float,
voff  : float
)

```

Arguments

ua, va
vector arrays (input) of 2 or more dimensions (last two dimensions must be nlata x nlona and values must be in ascending latitude order)
ub, vb
vector arrays (output) of 2 or more dimensions (last two dimensions must be nlatb x nlonb, values will be in ascending latitude order)
uoff, voff
vector arrays (input or output depending on procedure) of 2 or more dimensions (last two dimensions must be jlat x ilon, values must/will be in ascending latitude order)
ureg, vreg
vector arrays (input or output depending on procedure) of 2 or more dimensions (last two dimensions must be jlat1 x ilon, where jlat1 is jlat+1, values must/will be in ascending latitude order)
twave
scalar integer (input) indicating the optional wave truncation:
twave = 0 => exact interpolation
twave > 0 => exact interpolation and triangular truncation at twave
twave < 0 => exact interpolation, triangular truncation at twave and spectral coefficient tapering (the effect is to smooth the data)

Description

Fixed or regular grids have grid points that align with the Grenwich meridian and the equator. Eg: a 2.5 x 2.5 degree grid will have values at the equator:
```               (-90  ,0), (-90,  2.5),..., (-90,  357.5)
(-87.5,0), (-87.5,2.5),..., (-87.5,357.5)
.
(0,0), (0,2.5), (0,5.0),..., (0,357.5)
(2.5,0),(2.5,2.5),..., (2.5,357.5)
```
For a 2.5 degree fixed/regular grid there are 73 latitude points and 144 longitude points. Both pole points are present.

Fixed offset grids are grids 'offset' from Grenwich meridian and equator. For example, a 2.5 x 2.5 degree fixed-offset grid has values at:

```               (-88.75,1.25), (-88.75,3.75),..., (-88.75,357.5)
.
(1.25,1.25),   (1.25,3.75),...,(1.25,358.75)
(3,75,1.25),   (3.75,3.75),...,(3.75,358.75)
```
For a 2.5 degree fixed-offset grid there are 72 latitude points and 144 longitude points. There are no pole points.

g2gshv interpolates a vector pair from one Gaussian grid (ua,va) to another (ub,vb) (optional truncation) using spherical harmonics. The output array dimensions must be the same as the input array dimensions, except nlata and nlona are replaced by nlatb and nlonb.

g2fshv interpolates a vector pair on a Gaussian grid (ua,va) to a fixed grid (ub,va) using spherical harmonics. The output array dimensions must be the same as the input array dimensions, except nlata and nlona are replaced by nlatb and nlonb.

f2gshv interpolates a vector pair on a fixed grid (ua,va) to a Gaussian grid (ub,vb) (optional truncation) using spherical harmonics. The output array dimensions must be the same as the input array dimensions, except nlata and nlona are replaced by nlatb and nlonb.

f2fshv interpolates a vector pair from one fixed grid (ua,va) to another (ub,vb) using spherical harmonics. The output array dimensions must be the same as the input array dimensions, except nlata and nlona are replaced by nlatb and nlonb.

fo2fshv interpolates a vector pair on a fixed-offset grid (uoff,voff) (including pole points) to a fixed grid (ureg,vreg) using spherical harmonics. The output array dimensions must be the same as the input array dimensions, except jlat is replaced by jlat+1. For example, a 5 degree fixed-offset grid would have dimensions nlata=36, nlona=72, and the return fixed grid would have dimensions nlatb=37, nlonb=72.

f2foshv interpolates a vector pair on a fixed grid (ureg,vreg) (including pole points) to a fixed-offset grid (uoff,voff) using spherical harmonics. The output array dimensions must be the same as the input array dimensions, except jlat1 is replaced by jlat1-1. For example, a 5 degree fixed grid would have dimensions nlata=37, nlona=72, and the return fixed-offset grid would have dimensions nlatb=36, nlonb=72.

Arrays which have dimensions [...] 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

ier is equal to:
4 or 10 if nlona (ilon) is less than 4
5 or 10 if nlata (jlat) is less than 3
8 if nlonb is less than 4
9 if nlatb is less than 3

Reference Manual Control Panel

\$Revision: 1.13 \$ \$Date: 1999/02/23 15:59:23 \$