Cloud pattern metrics toolkit

cloud-organisation, python
pip install cloudmetrics==0.3.0



cloudmetrics (pip install) DOI

The cloudmetrics package contains python routines to compute metrics from 2D cloud fields to characterise cloud patterns in these fields. Most methods operate on a cloud-mask (i.e. a boolean true-false field) indicating where clouds exist, some work on individually labelled (with a unique integer ID) cloud objects (which can be produced from a cloud-mask) and finally some work on 2D cloud scalar-fields (defining for example the cloud-liquid water or cloud-top height).

NOTE: the cloudmetrics package contained in this repository is refactored from work published in Janssens et al 2021, this was done to make the routines implemented more accessible by external tools and to ensure consistency. Not all functionality has been retained or fully refactored, in particular functionality to allow for bulk-processing of input files is in the cloudmetrics-pipline package. Progress on the refactoring can be followed in issue #20. The version published in Janssens et al 2021 is available tagged as version v0.1.0.

Implemented metrics

The table below gives an overview over which metrics are avaiable in the cloudmetrics package and what input each metric takes.

function within cloudmetrics mask object_labels scalar_field
mask.cloud_fraction ✔️
mask.fractal_dimension ✔️
mask.open_sky ✔️
mask.orientation ✔️
mask.network_nn_dist TODO
mask.cop ✔️† ✔️
mask.csd TODO TODO
objects.iorg ✔️† ✔️
objects.max_length_scale ✔️† ✔️
objects.mean_eccentricity ✔️† ✔️
objects.mean_length_scale ✔️† ✔️
objects.mean_perimeter_length ✔️† ✔️
objects.rdf TODO TODO
objects.scai ✔️† ✔️
scalar.spectral_anisotropy #1 ✔️
scalar.spectral_length_median#1 ✔️
scalar.spectral_length_moment,#1 ✔️
scalar.spectral_slope#1 ✔️
scalar.spectral_slope_binned#1 ✔️
scalar.woi1 ✔️
scalar.woi2 ✔️
scalar.woi3 ✔️
scalar.mean optional ✔️
scalar.var optional ✔️
scalar.std optional ✔️
scalar.skew optional ✔️
scalar.kurtosis optional ✔️

†: for convenience object-based scalars are also made avaiable to operate directly on masks, for example objects.max_length_scale(object_labels=...) can be called with a mask as mask.max_object_length_scale(mask=...) and objects.iorg(object_labels=...) can be called with mask.iorg_objects(mask=...).

#1: spectral metrics currently operate on the relevant power spectral densities, which must first be computed:

wavenumbers, psd_1d_radial, psd_1d_azimuthal = scalar.compute_spectra(...)
spectral_length_moment = scalar.spectral_length_moment(wavenumbers, psd_1d_radial)

Alternatively, all spectral metrics can be computed simultaneously following the standard convention with spectral_metrics = scalar.compute_all_spectral(scalar_field). need refactoring to take scalar_field as input


To install the most recent version of cloudmetrics from pypi you can use pip:

$> pip install cloudmetrics

If you plan to add/modify cloudmetrics (contribution via pull-requests are very welcome!) you should check out the development notes for how to get set up with a local copy of the codebase.


To use the cloudmetrics package simply import cloudmetrics and use the metric function you are interested in:

import cloudmetrics

iorg = cloudmetrics.mask.iorg_objects(mask=da_cloudmask, periodic_domain=False)

As you can see in the table above the metrics are organised by the input they take, either object masks, labelled-object arrays and/or 2D scalar fields you want to perform reductions on.

Note on periodic domains: internally cloudmetrics represents objects on periodic domains by doubling the xy-size of any input mask provided, and moving any objects that straddle the boundary to ensure they are spatially contiguous. This means that all functions which take 2D arrays of object-labels as input assume that all labelled objects are spatially contiguous and that the provided input is actually 2*nx x 2*ny (for an actual input domain spanning nx by nx). All metric functions that operate on masks handle the domain-doubling internally and so do not require any modification to the masks before calling.