Using xgcm.transform to interpolate to isopycnal space

Contents

Using `xgcm.transform` to interpolate to isopycnal space#

%load_ext watermark

import numpy as np
import xarray as xr
import xgcm

import pop_tools

%watermark -iv

xgcm     : 0.8.1
pop_tools: 2023.3.0.post2+dirty
xarray   : 2023.6.0
numpy    : 1.24.4

Visualize surface density field#

(xds.rho - 1000).isel(z_t=0).plot(robust=True)

<matplotlib.collections.QuadMesh at 0x7f7cdbf0fcd0>

../_images/6038f9680e3497c8d20e81e62a118d19aa19d848732797e702f1afbe667823b3.png

Regrid to density space using `grid.transform`#

See https://xgcm.readthedocs.io/en/latest/transform.html for more

regridded = grid.transform(
    xds.TEMP,
    axis="Z",
    target=np.arange(25, 30, 0.5),
    target_data=xds.rho - 1000,
    method="linear",
)

/home/docs/checkouts/readthedocs.org/user_builds/pop-tools/conda/latest/lib/python3.9/site-packages/xgcm/grid.py:989: FutureWarning: From version 0.8.0 the Axis computation methods will be removed, in favour of using the Grid computation methods instead. i.e. use `Grid.transform` instead of `Axis.transform`
  warnings.warn(

/home/docs/checkouts/readthedocs.org/user_builds/pop-tools/conda/latest/lib/python3.9/site-packages/numba/np/ufunc/gufunc.py:171: RuntimeWarning: invalid value encountered in _interp_1d_linear
  return self.ufunc(*args, **kwargs)

Visualize temperature on a single isopycnal surface#

regridded.isel(rho=5).plot(robust=True)

<matplotlib.collections.QuadMesh at 0x7f7cdb7632b0>

../_images/4f4c449857347c58709fc770fc6fc3a4b52392f9f150940e872c40c9f286ebe1.png

Find depth of isopycnal surface#

regridded.coords["z_t"] = grid.transform(
    xds.z_t.broadcast_like(xds.rho),
    axis="Z",
    target=np.arange(24, 30, 0.5),
    target_data=xds.rho - 1000,
    method="linear",
)
regridded.z_t.isel(rho=5).plot(robust=True)

<matplotlib.collections.QuadMesh at 0x7f7cdb6baa60>

../_images/f7edda609f1e6a58808a80d148d31620a3e958f9fe4ae4ac7af0182ef4ff4574.png