pyart.retrieve.detect_ml#

pyart.retrieve.detect_ml(radar, gatefilter=None, fill_value=None, refl_field=None, rhohv_field=None, ml_field=None, ml_pos_field=None, iso0_field=None, max_range=20000, detect_threshold=0.02, interp_holes=False, max_length_holes=250, check_min_length=True, get_iso0=False)[source]#

Detects the melting layer (ML) using the reflectivity and copolar correlation coefficient. Internally it uses RHIs

Paremeters#

radarRadar

A Radar class instance

gatefilterGateFilter, optional

A GateFilter indicating radar gates that should be excluded

fill_valuefloat, optional

Value indicating missing or bad data in differential phase field, if not specified, the default in the Py-ART configuration file will be used

refl_fieldstr, optional

Reflectivity field. If None, the default field name must be specified in the Py-ART configuration file.

rhohv_fieldstr, optional

Copolar correlation coefficient field. If None, the default field name must be specified in the Py-ART configuration file.

ml_fieldstr, optional

Melting layer field. If None, the default field name must be specified in the Py-ART configuration file.

ml_pos_fieldstr, optional

Melting layer height field. If None, the default field name must be specified in the Py-ART configuration file.

iso0_fieldstr, optional

height respect to the iso0 field.

max_rangefloat, optional

the max. range from the radar to be used in the ML determination

detect_thresholdfloat, optional

the detection threshold (see paper), you can play around and see how it affects the output. Lowering the value makes the algorithm more sensitive but increases the number of erroneous detections.

interp_holesbool, optional

Flag to allow for interpolation of small holes in the detected ML

max_length_holesfloat, optional

The maximum size of holes in the ML for them to be interpolated

check_min_lengthbool, optional

If true, the length of the detected ML will be compared with the length of the valid data and the ML will be kept only if sufficiently long

get_iso0bool

returns height w.r.t. freezing level top for each gate in the radar volume.

returns:

  • ml_obj (radar-like object) – A radar-like object containing the field melting layer height with the bottom (at range position 0) and top (at range position one) of the melting layer at each ray

  • ml_dict (dict) – A dictionary containg the position of the range gate respect to the melting layer and metadata

  • iso0_dict (dict or None) – A dictionary containing the distance respect to the melting layer and metadata

  • all_ml (dict) – Dictionary containing internal parameters in polar and cartesian coordinates

  • Reference

  • ———-

  • Wolfensberger, D. , Scipion, D. and Berne, A. (2016), Detection and

  • characterization of the melting layer based on polarimetric radar scans.

  • Q.J.R. Meteorol. Soc., 142 (108-124. doi:10.1002/qj.2672)