# `opendrift.readers.roppy.depth`

Vertical structure functions for ROMS

`sdepth()`

Depth of s-levels

`zslice()`

Slice a 3D field in s-coordinates to fixed depth

`multi_zslice()`

Slice a 3D field to several depth levels

`z_average()`

Vertical average of a 3D field

`s_stretch()`

Compute vertical stretching arrays Cs_r or Cs_w

## Module Contents

### Functions

 `sdepth`(H, Hc, C, stagger='rho', Vtransform=1) Depth of s-levels `sdepth_w`(H, Hc, cs_w) Return depth of w-points in s-levels `zslice`(F, S, z) Vertical slice of a 3D ROMS field `multi_zslice`(F, S, Z) Slice a 3D ROMS field to fixed depth `z_average`(F, z_r, z0, z1) Slice a 3D ROMS field to fixed depth `s_stretch`(N, theta_s, theta_b, stagger='rho', Vstretching=1) Compute a s-level stretching array `s_stretch_w`(N, theta_s, theta_b, Vstretching=1) Obsolete use s_stretch instead

Depth of s-levels

Harraylike

Bottom depths [meter, positive]

Hcscalar

Critical depth

cs_r1D array

s-level stretching curve

stagger : [ ‘rho’ | ‘w’ ]

Vtransform[ 1 | 2 ]

defines the transform used, defaults 1 = Song-Haidvogel

Returns an array with ndim = H.ndim + 1 and shape = cs_r.shape + H.shape with the depths of the mid-points in the s-levels.

Typical usage:

```>>> fid = Dataset(roms_file)
>>> H = fid.variables['h'][:, :]
>>> C = fid.variables['Cs_r'][:]
>>> Hc = fid.variables['hc'].getValue()
>>> z_rho = sdepth(H, Hc, C)
```

Return depth of w-points in s-levels

Kept for backwards compatibility use sdepth(H, Hc, cs_w, stagger=’w’) instead

Vertical slice of a 3D ROMS field

Vertical interpolation of a field in s-coordinates to (possibly varying) depth level

F : array with vertical profiles, first dimension is vertical

S : array with depths of the F-values,

zDepth level(s) for output, scalar or `shape = F.shape[1:]`

The z values should be negative

Return value : array, shape = F.shape[1:], the vertical slice

Example: H is an array of depths (positive values) Hc is the critical depth C is 1D containing the s-coordinate stretching at rho-points returns F50, interpolated values at 50 meter with F50.shape = H.shape

```>>> z_rho = sdepth(H, Hc, C)
>>> F50 = zslice(F, z_rho, -50.0)
```

Slice a 3D ROMS field to fixed depth

Vertical interpolation of a field in s-coordinates to fixed vertical level

F : array of with vertical profiles, first dimension is vertical

Sarray with depth of s-levels (at rho-points)

1D (constant depth) or S.shape = F.shape

Z : single depth value, negative

Returns : array, `shape = F.shape[1:]` the vertical slice

Slice a 3D ROMS field to fixed depth

Vertical interpolation of a field in s-coordinates to fixed vertical level

Farray

Vertical profiles, first dimension is vertical

z_rarray

Depth of s-levels (at rho-points), requires z_r.shape = F.shape

z0, z1floats

Single depth values with z0 <= z1 <= 0

return valuearray

shape = F.shape[1:], the vertical average

Compute a s-level stretching array

N : Number of vertical levels

theta_s : Surface stretching factor

theta_b : Bottom stretching factor

stagger : “rho”|”w”

Vstretching : 1|2|4