The datain module.

This module implements functions to various input tasks for monc_utils.

New at 0.2

1. The ability to read in spatial derivatives of variables. The syntax is e.g. 'dbydx(th_L)'. This will read in th_L, itself a derived variable, and produce an x derivative.

   • Using get_data() the derivative on it’s native grid (i.e. a centred difference) is returned, with the name requested.

   • Using get_data_on_grid() the result is interpolated to the required grid and the name appended _on_grid, with grid the requested grid.

   • Nesting is allowed, e.g. 'dbydy(dbydx(th_L))'.

New at 0.1

1. Relocated to monc_utils.io.

Detailed Module Contents

The entire module is documented below.

Created on Mon Aug 2 11:01:11 2021.

@author: Peter Clark

monc_utils.io.datain.correct_grid_and_units(var_name: str, vard: DataArray, source_dataset: Dataset, options: Optional[dict] = None)

Correct input grid specification.

Parameters:

• var_name (str) – Name of variable to retrieve.

• vard (xarray.core.dataarray.DataArray) – Input (at least 2D) data.

• source_dataset (xarray.core.dataset.Dataset) – Source dataset for vard

• options (dict(optional - default=None)) – Options possibly used are ‘dx’ and ‘dy’.

Returns:

vard – Required data with corrected grid.

Return type:

xarray

monc_utils.io.datain.get_derived_vars(source_dataset, ref_dataset, var_name: str, derived_vars: dict, options: Optional[dict] = None)

Get data from source_dataset and compute required variable.

Parameters:

• source_dataset (xarray Dataset) – Input (at least 2D) data.

• ref_dataset (xarray Dataset) – Contains reference profiles. Can be None.

• var_name (str) – Name of variable to retrieve.

• derived_vars (dict) – Maps var_name to function name and argument list.

• options (dict (optional - default=None)) – Options. Options possibly used are ‘dx’ and ‘dy’.

Returns:

vard – DESCRIPTION.

Return type:

TYPE

monc_utils.io.datain.get_data(source_dataset, ref_dataset, var_name: str, options: Optional[dict] = None, allow_none: bool = False)

Extract data or derived data field from source NetCDF dataset.

If var_name is in source_dataset it is retrieved; if one of the primary variables with a key in var_properties the grid is corrected. Otherwise, it is assumed to be on a ‘p’ point.

Currently written for MONC data, enforcing C-grid. Returned coords are ‘x_p’, ‘x_u’, ‘y_p’, ‘y_v’, ‘z_w’, ‘z_p’. Coordinate x- and -y values are retrieved from the MONC options_database in source_dataset or from ‘dx’ and ‘dy’ in options otherwise.

Alternative names of variables can be supplied in options[‘aliases’] as a list of strings. If var_name is not found in source_dataset the first alias present in source_dataset is retrieved and renamed to var_name.

Currently supported derived data are specified if the thermodynamics module.

The special var_name ‘thref’ retrieves the reference theta profile.

Parameters:

• source_dataset (xarray Dataset) – Input (at least 2D) data.

• ref_dataset (xarray Dataset) – Contains reference profiles. Can be None.

• var_name (str) – Name of variable to retrieve.

• options (dict (optional - default=None)) – Options possibly used are ‘dx’ and ‘dy’.

• allow_none (bool (optional - default=False)) – If True, return None if not found.

Returns:

vard – Output data field.

Return type:

xarray

@author: Peter Clark

monc_utils.io.datain.get_and_transform(source_dataset, ref_dataset, var_name, options=None, grid='p')

Extract data from dataset and transform to alternative grid.

See get_data for derived variables.

Parameters:

• source_dataset (xarray Dataset) – Input (at least 2D) data.

• ref_dataset (xarray Dataset) – Contains reference profiles. Can be None.

• var_name (str) – Name of variable to retrieve.

• options (dict (optional - default=None)) – Options. Options possibly used are ‘dx’ and ‘dy’.

• grid (str, optional) – Destination grid ‘u’, ‘v’, ‘w’ or ‘p’. Default is ‘p’.

Returns:

var – Output data field.

Return type:

xarray

@author: Peter Clark

monc_utils.io.datain.get_data_on_grid(source_dataset, ref_dataset, var_name, derived_dataset=None, options=None, grid='p')

Find data from source_dataset remapped to destination grid.

Uses data from derived_dataset if present, otherwise uses get_and_transform to input from source_dataset and remap grid. In this case, if options[‘save_all’]==’yes’, save the remapped data to derived_dataset.

See get_data for derived variables.

Parameters:

• source_dataset (xarray Dataset) – Input (at least 2D) data.

• ref_dataset (xarray Dataset) – Contains reference profiles. Can be None.

• var_name (str) – Name of variable to retrieve.

• derived_dataset (dict, optional) – ‘ds’ points to xarray Dataset, ‘file’ to output file path.

• options (dict, (optional - default=None)) – Options. Options possibly used are ‘dx’ and ‘dy’.

• grid (str, optional) – Destination grid ‘u’, ‘v’, ‘w’ or ‘p’. Default is ‘p’.

Returns:

var – Output data field.

Return type:

xarray

@author: Peter Clark

monc_utils.io.datain.get_pref(source_dataset, ref_dataset, options=None)

Get reference pressure profile for source_dataset.

Calculate from ref_dataset or from surface_press in source_dataset options_database and options[‘th_ref’].

Parameters:

• source_dataset (netCDF4 file) – MONC output file.

• ref_dataset (netCDF4 file or None) – MONC output file containing 1D variable prefn.

• options (dict (optional - default=None)) – Options. Options possibly used are th_ref.

Return type:

pref

monc_utils.io.datain.get_thref(ref_dataset, options=None)

Get thref profile from ref_dataset.

Parameters:

• ref_dataset (netCDF4 file or None) – MONC output file containing pref

• options (dict) – Options. Options possibly used are th_ref.

Returns:

thref – Reference theta constant or profile

Return type:

float or float array.

Created on Mon Aug 2 11:21:15 2021

@author: Peter Clark