A Python-based Radar Data Processing System for the NASA GPM Ground
Validation Program
Abstract
The science community’s progression toward Python as a primary
programing language, facilitated NASA’s Global Precipitation Measurement
(GPM) Ground Validation (GV) Program to develop a Python-based radar
processing system, GVradar. GVradar consists of two modules:
Dual-Polarimetric Quality Control (DPQC) and dual-polarimetric
precipitation product generation (dp_products). Both modules take full
advantage of the open-source Python Atmospheric Radiation Measurement
(ARM) Radar Toolkit (Py-ART) and Colorado State University’s Radar Tools
(CSU Radar Tools). Within DPQC, parameter threshold gate filters are
utilized to identify and remove non-precipitating echoes based on
freezing level, beam height, or by user defined sector. Additional DPQC
capabilities include unfolding of Differential Phase (Φdp), Specific
Differential Phase (Kdp) retrieval, velocity de-aliasing, and
application of calibration offsets. Precipitation products generated
with CSU Radar Tools include HIDRO Rain Rate (RC) and Hydrometeor
Identification (FH). Additional products include GPM-GV’s mass weighted
mean diameter (Dm) and normalized intercept parameter
(Nw). Dm and Nw
retrievals were computed from empirical equations using disdrometer
derived Zdr data obtained during GPM field experiments. The recommended
method of executing GVradar is to use a user designated parameter
dictionary, however the code will run with default settings. The use of
a dictionary allows the user to optimize QC thresholds, specify fields
to generate, and select output and plotting options. The ability of
GVradar to retrieve sounding data from the Rapid Refresh (RAP) model
allows DPQC to be applied and dp_products to be generated in near
real-time. NASA’s Dual Polarimetric (NPOL) radar is currently using
GVradar to display data in near real-time. GPM-GV developed GVradar as a
user-friendly open-source radar processing tool that is freely available
to the scientific community.