pyart.retrieve.melting_layer_giangrande#

pyart.retrieve.melting_layer_giangrande(radar, nVol=3, maxh=6000.0, hres=50.0, rmin=1000.0, elmin=4.0, elmax=10.0, rhomin=0.75, rhomax=0.94, zhmin=20.0, hwindow=500.0, mlzhmin=30.0, mlzhmax=50.0, mlzdrmin=1.0, mlzdrmax=5.0, htol=500.0, ml_bottom_diff_max=1000.0, time_accu_max=1800.0, nml_points_min=None, wlength=20.0, percentile_bottom=0.3, percentile_top=0.9, interpol=True, time_nodata_allowed=3600.0, refl_field=None, zdr_field=None, rhv_field=None, temp_field=None, iso0_field=None, ml_field=None, ml_pos_field=None, temp_ref=None, get_iso0=False, ml_global=None)[source]#

Detects the melting layer following the approach by Giangrande et al (2008)

Parameters:

radar (radar) – radar object

Other Parameters:

  • nVol (int) – Number of volume scans to aggregate

  • maxh (float) – Maximum possible height of the melting layer [m MSL]

  • hres (float) – Step of the height of the melting layer [m]

  • rmin (float) – Minimum range from radar where to look for melting layer contaminated range gates [m]

  • elmin, elmax (float) – Minimum and maximum elevation angles where to look for melting layer contaminated range gates [degree]

  • rhomin, rhomax (float) – min and max rhohv to consider pixel potential melting layer pixel

  • zhmin (float) – Minimum reflectivity level of a range gate to consider it a potential melting layer gate [dBZ]

  • hwindow (float) – Maximum distance (in range) from potential melting layer gate where to look for a maximum [m]

  • mlzhmin, mlzhmax (float) – Minimum and maximum values that a peak in reflectivity within the melting layer may have to consider the range gate melting layer contaminated [dBZ]

  • mlzdrmin, mlzdrmax (float) – Minimum and maximum values that a peak in differential reflectivity within the melting layer may have to consider the range gate melting layer contaminated [dB]

  • htol (float) – maximum distance from the iso0 coming from model allowed to consider the range gate melting layer contaminated [m]

  • ml_bottom_dif_max (float) – Maximum distance from the bottom of the melting layer computed in the previous time step to consider a range gate melting layer contaminated [m]

  • time_accu_max (float) – Maximum time allowed to accumulate data from consecutive scans [s]

  • nml_points_min (int) – minimum number of melting layer points to consider valid melting layer detection

  • wlength (float) – length of the window to select the azimuth angles used to compute the melting layer limits at a particular azimuth [degree]

  • percentile_bottom, percentile_top (float [0,1]) – percentile of ml points above which is considered that the bottom of the melting layer starts and the top ends

  • interpol (bool) – Whether to interpolate the obtained results in order to get a value for each azimuth

  • time_nodata_allowed (float) – The maximum time allowed for no data before considering the melting layer not valid [s]

  • refl_field, zdr_field, rhv_field, temp_field, iso0_field (str) – Inputs. Field names within the radar object which represent the horizonal reflectivity, the differential reflectivity, the copolar correlation coefficient, the temperature and the height respect to the iso0 fields. A value of None for any of these parameters will use the default field name as defined in the Py-ART configuration file.

  • ml_field (str) – Output. Field name which represents the melting layer field. A value of None will use the default field name as defined in the Py-ART configuration file.

  • ml_pos_field (str) – Output. Field name which represents the melting layer top and bottom height field. A value of None will use the default field name as defined in the Py-ART configuration file.

  • temp_ref (str) – the field use as reference for temperature. Can be temperature or height_over_iso0. If None, it excludes model data from the algorithm.

  • get_iso0 (bool) – returns height w.r.t. freezing level top for each gate in the radar volume.

  • ml_global – stack of previous volume data to introduce some time dependency. Its max size is controlled by the nVol parameter. It is always in (pseudo-)RHI mode.

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

  • ml_global (dict or None) – stack of previous volume data to introduce some time dependency. Its max size is controlled by the nVol parameter. It is always in (pseudo-)RHI mode.

References

Giangrande, S.E., Krause, J.M., Ryzhkov, A.V.: Automatic Designation of the Melting Layer with a Polarimetric Prototype of the WSR-88D Radar, J. of Applied Meteo. and Clim., 47, 1354-1364, doi:10.1175/2007JAMC1634.1, 2008