Xarray engine: variable key¶

The variable_key option in to_xarray() controls which metadata key is used to name the Xarray Dataset variables. In the default profile earthkit, it is set to "parameter.variable".

Please note it is also possible to generate an Xarray with a single DataArray containing all the parameters from a fieldlist. See e.g. the Xarray engine: mono variable notebook for details.

[1]:

import earthkit.data as ekd

ds_fl = ekd.from_source("sample", "pl.grib").to_fieldlist()
ds = ds_fl.to_xarray()
ds

Using remapping¶

Using the remapping option can come in handy when there are parameters with different level types in the input data.

[2]:

ds_fl = ekd.from_source("sample", "mixed_pl_sfc.grib").to_fieldlist()
ds = ds_fl.to_xarray(variable_key="p_l", remapping={"p_l": "{parameter.variable}_{vertical.level}"})
ds

We can take it one step further and define a metadata key that combines the parameter name, the level and the level type into a single key.

[3]:

ds_fl = ekd.from_source("sample", "mixed_pl_sfc.grib").to_fieldlist()
ds = ds_fl.to_xarray(
    variable_key="p_l_t", remapping={"p_l_t": "{parameter.variable}_{vertical.level}_{vertical.level_type}"}
)
ds

This technique is particularly useful when the same parameter is available on multiple level types in the input data. In this case using just the parameter name as the variable_key (the default) does not result in a full hypercube, however the remappings that we used above do.

[4]:

ds_fl = ekd.from_source("sample", "mixed_pl_ml.grib").to_fieldlist()
ds = ds_fl.to_xarray(
    variable_key="p_l_t", remapping={"p_l_t": "{parameter.variable}_{vertical.level}_{vertical.level_type}"}
)
ds