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NOAA Research 2007 Outstanding Scientific Paper Awards
“The Joint Polarization Experiment: Polarimetric Rainfall Measurements and Hydrometeor Classification”
ABSTRACT
As part of the evolution and future enhancement of the Next Generation Weather
Radars (NEXRAD), the National Severe Storms Laboratory recently upgraded
the KOUN Weather Surveillance Radar-1988 Doppler (WSR-88D) to include a
polarimetric capability. The proof of concept was tested in central Oklahoma
during a 1-yr demonstration project referred to as the Joint Polarization
Experiment (JPOLE). This paper presents an overview of polarimetric algorithms
for rainfall estimation and hydrometeor classification and their performance
during JPOLE. The quality of rainfall measurements is validated on a large
dataset from the Oklahoma Mesonet and Agricultural Research Service Micronet
rain gauge networks. The comparison demonstrates that polarimetric rainfall
estimates are often dramatically superior to those provided by conventional
rainfall algorithms. Using a synthetic R(Z, KDP, ZDR)
polarimetric rainfall relation, rms errors are reduced by a factor of 1.7
for point measurements and 3.7 for areal estimates [when compared
to results from a conventional R(Z) relation]. Radar
data quality improvement, hail identification, rain/snow discrimination,
and polarimetric tornado detection are also illustrated for selected events. FULL
TEXT 
Instrumentation for rainfall estimation in Oklahoma. The Mesonet includes 115 gauges with an average gauge spacing of 30 km (Brock et al. 1995); the Micronet consists of 42 gauges with an average gauge spacing of 5 km. Both networks provide 5-min rain accumulation data. (larger image)
The Z–ZDR scatterplots for different types of snow. Two curves confine the area where the majority of the cold-season rain Z–ZDR pairs are usually observed. (larger image)
Composite plot of Z, ZDR, ρhv, for the Moore/ Southeast Oklahoma City tornado on 8 May 2003 (2228 UTC, E1 = 1.5º). The tornado signature in ZDR and ρhv is at the tip of the hook echo (X = 9 km, Y = 18 km). (larger image)
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10/22/07