pysteps.cascade¶
Methods for constructing bandpass filters and decomposing 2d precipitation fields into different spatial scales.
pysteps.cascade.interface¶
Interface for the cascade module.
get_method(name) |
Return a callable function for the bandpass filter or decomposition method corresponding to the given name. |
pysteps.cascade.bandpass_filters¶
Bandpass filters for separating different spatial scales from two-dimensional images in the frequency domain.
The methods in this module implement the following interface:
filter_xxx(shape, n, optional arguments)
where shape is the shape of the input field, respectively, and n is the number of frequency bands to use.
The output of each filter function is a dictionary containing the following key-value pairs:
| Key | Value |
|---|---|
| weights_1d | 2d array of shape (n, r) containing 1d filter weights for each frequency band k=1,2,…,n |
| weights_2d | 3d array of shape (n, M, int(N/2)+1) containing the 2d filter weights for each frequency band k=1,2,…,n |
| central_freqs | 1d array of shape n containing the central frequencies of the filters |
where r = int(max(N, M)/2)+1
By default, the filter weights are normalized so that for any Fourier wavenumber they sum to one.
Available filters¶
filter_uniform(shape, n) |
A dummy filter with one frequency band covering the whole domain. |
filter_gaussian(shape, n[, l_0, …]) |
Implements a set of Gaussian bandpass filters in logarithmic frequency scale. |
pysteps.cascade.decomposition¶
Methods for decomposing two-dimensional images into multiple spatial scales.
The methods in this module implement the following interface:
decomposition_xxx(X, filter, **kwargs)
where X is the input field and filter is a dictionary returned by a filter
method implemented in pysteps.cascade.bandpass_filters.
Optional parameters can be passed in
the keyword arguments. The output of each method is a dictionary with the
following key-value pairs:
| Key | Value |
|---|---|
| cascade_levels | three-dimensional array of shape (k,m,n), where k is the number of cascade levels and the input fields have shape (m,n) |
| means | list of mean values for each cascade level |
| stds | list of standard deviations for each cascade level |
Available methods¶
decomposition_fft(X, filter, **kwargs) |
Decompose a 2d input field into multiple spatial scales by using the Fast Fourier Transform (FFT) and a bandpass filter. |