Segmentation Output

Segmentation outputs a mask (iris.cube.Cube and in the future xarray.DataArray) with the same dimensions as the input field, where each segmented area has the same ID as its corresponding feature (see feature column in Feature Detection Output). Note that there are some cases in which a feature is not attributed to a segmented area associated with it (see Features without segmented areas).

Segmentation also outputs the same pandas dataframe as obtained by Feature Detection (see Feature Detection Basics) but with one additional column:

tobac Segmentation Output Variables

Variable Name	Description	Units	Type
ncells	Total number of grid points that belong to the segmented area associated with feature.	n/a	int64

One can optionally get the bulk statistics of the data points belonging to each segmented feature (i.e. either the 2D area or the 3D volume assigned to the feature). This is done using the statistics parameter when calling :ufunc:`tobac.segmentation.segmentation` . The user-defined metrics are then added as columns to the output dataframe, for example:

tobac Segmentation Output Variables

Variable Name	Description	Units	Type
feature_mean	Mean of feature data points	same as input field	float
feature_max	Maximum value of feature data points	same as input field	float
feature_min	Minimum value of feature data points	same as input field	float
feature_sum	Sum of feature data points	same as input field	float
major_axis_length	The length of the major axis of the ellipse that has the same normalized second central moments as the feature area	number of grid cells, multiply by dx to get distance unit	float
feature_percentiles	Percentiles from 0 to 100 (with increment 1) of feature data distribution	same as input field	ndarray

Note that these statistics refer to the data fields that are used as input for the segmentation. It is possible to run the segmentation with different input (see transform segmentation) data to get statistics of a feature based on different variables (e.g. get statistics of cloud top temperatures as well as rain rates for a certain storm object).