Cooperative Institute for Mesoscale Meteorological Studies

RESEARCH

NOAA Strategic Goal 3: Serve Society’s Need for Weather and Water Information

Doppler Weather Radar Research and Development

NSSL Project 5 – Investigation of the Use of Dual-Polarization Radar to Improve Quantitative Precipitation Estimation for Improving Flash Flood and Flood Detection, Warnings, and Forecasts:

Polarimetric Hydrometeor Classification and Rainfall Estimation for Better Detecting and Forecasting High-Impact Weather Phenomena Including Flash Floods

Ryzhkov (primary – CIMMS at NSSL), Giangrande, Krause, Park, Schuur, Melnikov

Funding Type: CIMMS Task II

Objectives
Develop and validate polarimetric algorithms for quantitative precipitation estimation (QPE) and hydrometeor classification (HCA); explore the utility of polarimetric QPE and HCA for shorter wavelength (C- and X-band) radars.

Accomplishments
The latest versions of the polarimetric algorithms for hydrometeor classification and rainfall estimation (HCA v2 and QPE v2 respectively) have been transferred to NWS for operational implementation in the first deployment of polarimetric WSR-88D radars. The operational versions of the algorithms have been tested on the extensive KOUN dataset including rain events observed during 2002-2005.

The results of polarimetric echo classification have been integrated into the study to investigate the performance of radar rainfall estimation contingent on hydrometeor type. Separate statistics are obtained for widespread stratiform and warm season convective events to determine the significance of melting layer contamination. A new method for polarimetric rainfall estimation that capitalizes on the results of echo classification exhibits better performance than the conventional WSR-88D technique up to the distances of 180 200 km.

The S-band versions of HCA and QPE algorithms have been adapted for C band and tested on a number of storms observed in Ontario, Canada, with the King City C-band polarimetric radar and in Alabama using the data collected by the EEC Sidpol dual-polarization radar.

This project is ongoing.

Publications
Ryzhkov, A.V., 2007: The impact of beam broadening on the quality of radar polarimetric data. J. Atmos. Oceanic Technol., 24, 729- 744.

Ryzhkov, A.V., and D.S. Zrnic, 2007: Depolarization in ice crystals and its effect on radar polarimetric measurements. J. Atmos. Oceanic Technol., 24, 1215-1230.

Giangrande, S.E., J.M. Krause, and A.V. Ryzhkov, 2007: Automatic designation of the melting layer with a polarimetric prototype of the WSR-88D radar. J. Appl. Meteor., submitted.

Giangrande, S., and A. Ryzhkov, 2007: Estimation of rainfall based on the results of polarimetric echo classification. J. Appl. Meteor., submitted.

Hudak, D., P. Rodriguez, G. W. Lee, A. Ryzhkov, F. Fabry, and N. Donaldson, 2006: Winter precipitation studies with a dual polarized C-band radar. Fourth European Conf. on Radar in Meteorology and Hydrology. Barcelona, Spain, 9-12.

Ryzhkov, A., D. Hudak, and J. Scott, 2006: A new polarimetric scheme for attenuation correction at C band. Fourth European Conf. on Radar in Meteorology and Hydrology. Barcelona, Spain, 29-32.

Ryzhkov, A., 2006: The effect of nonuniform beam filling on the quality of radar polarimetric data. Fourth European Conf. on Radar in Meteorology and Hydrology. Barcelona, Spain, 1-4.

Ryzhkov, A., and Zrnic, D., 2006: The impact of depolarization on polarimetric signatures in snow. Fourth European Conf. on Radar in Meteorology and Hydrology. Barcelona, Spain, 33-36.

Range dependencies of a bias and rms error of one-hour rainfall estimation performed by conventional and

Range dependencies of a bias and rms error of one-hour rainfall estimation performed by conventional and polarimetric algorithms. Polarimetric algorithm yields almost 2 times reduction in the rms error at relatively close distances from the radar.