pyart.filters.birds_gate_filter

pyart.filters.birds_gate_filter(radar, zdr_field=None, rhv_field=None, refl_field=None, vel_field=None, max_zdr=3.0, max_rhv=0.9, min_refl=0.0, max_refl=20.0, vel_lim=1.0, rmin=2000.0, rmax=25000.0, elmin=1.0, elmax=85.0)

Create a filter which removes data not suspected of being birds

Creates a gate filter in which the following gates are excluded:

• Gates where the instrument is transitioning between sweeps.

• Gates where the reflectivity is beyond min_refl and max_refl

• Gates where the co-polar correlation coefficient is above max_rhv

• Gates where the differential reflectivity is above max_zdr

• Gates where the Doppler velocity is within the interval given by +-vel_lim

• Gates where any of the above fields are masked or contain invalid values (NaNs or infs).

• Gates outside the range given by range min and range max

• If any of these three fields do not exist in the radar that fields filter criteria is not applied.

Parameters:

• radar (Radar) – Radar object from which the gate filter will be built.

• refl_field, zdr_field, rhv_field, vel_field (str) – Names of the radar fields which contain the reflectivity, differential reflectivity, co-polar correlation coefficient, and Doppler velocity from which the gate filter will be created using the above criteria. A value of None for any of these parameters will use the default field name as defined in the Py-ART configuration file.

• max_zdr, max_rhv (float) – Maximum values for the differential reflectivity and co-polar correlation coefficient. Gates in these fields above these limits as well as gates which are masked or contain invalid values will be excluded and not used in calculation which use the filter. A value of None will disable filtering based upon the given field including removing masked or gates with an invalid value. To disable the thresholding but retain the masked and invalid filter set the parameter to a value above the highest value in the field.

• min_refl, max_refl (float) – Minimum and maximum values for the reflectivity. Gates outside of this interval as well as gates which are masked or contain invalid values will be excluded and not used in calculation which use this filter. A value or None for one of these parameters will disable the minimum or maximum filtering but retain the other. A value of None for both of these values will disable all filtering based upon the reflectivity including removing masked or gates with an invalid value. To disable the interval filtering but retain the masked and invalid filter set the parameters to values above and below the lowest and greatest values in the reflectivity field.

• rmin, rmax (float) – Minimum and maximum ranges [m]

• elmin, elmax (float) – Minimum and maximum elevations [deg]

Returns:

gatefilter (GateFilter) – A gate filter based upon the described criteria. This can be used as a gatefilter parameter to various functions in pyart.correct.