Looking for References for R(KDP) Power Law Coefficients in _coeff_rkdp_table() (Py-ART)

General
1

Dear Open Radar community,

I am currently investigating the R(KDP) power-law relationships used in the pyart.retrieve.qpe module from the Py-ART library and would like to ask for your help in identifying the original references that support the coefficients defined in the internal function _coeff_rkdp_table():

def _coeff_rkdp_table():
coeff_rkdp_dict = dict()

# S band: Beard and Chuang coefficients
coeff_rkdp_dict.update({"S": (50.70, 0.8500)})

# C band: Beard and Chuang coefficients
coeff_rkdp_dict.update({"C": (29.70, 0.8500)})

# X band: Brandes coefficients
coeff_rkdp_dict.update({"X": (15.81, 0.7992)})

return coeff_rkdp_dict

These values are used in the generalized power-law equation:

R=aKDPb

However, despite comments in the code stating that the S- and C-band coefficients come from Beard and Chuang, and the X-band coefficients from Brandes, I have been unable to locate these articles.

In particular, I am looking for the source (preferably peer-reviewed) that supports:

  • S band: (50.70, 0.8500)
  • C band: (29.70, 0.8500)
  • X band: (15.81, 0.7992)

Do these coefficients come from published literature, or were they empirically derived from specific datasets (e.g., U.S. mid-latitude stratiform/convective events, ARM campaigns, etc.)?

Any help in tracing back the original references for these values would be greatly appreciated.

Best regards,
Elton J. Robaina da Silva