Editorial Type:
Article
Article Type:
Research Article

Discrimination between Rain and Snow with a Polarimetric Radar

A. V. Ryzhkov Cooperative Institute for Mesoscale Meteorological Studies, University of Oklahoma, Norman, Oklahoma

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D. S. Zrnic National Severe Storms Laboratory, Norman, Oklahoma

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Print Publication:
01 Oct 1998
DOI:
https://doi.org/10.1175/1520-0450(1998)037<1228:DBRASW>2.0.CO;2
Page(s):
1228–1240
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Abstract

Polarimetric signatures of snow precipitation for six Oklahoma snowstorms are examined. The available data consist of specific differential phase KDP, differential reflectivity ZDR, cross-correlation coefficient ρhv, and radar reflectivity factor Z. These data were obtained with the 10-cm-wavelength Cimarron polarimetric weather radar. The data suggest that in pure snow the average values of KDP and ZDR do not follow a systematic trend with change of the radar reflectivity factor if Z < 35 dBZ; this is not the case in rain. Precipitation is qualified as snow if the average ZDR is less than 0.2 dB for Z < 35 dBZ. The presence of a bright band with a pronounced ρhv minimum and ZDR maximum is a good discernible feature for discriminating between snow and rain. Thus, a localized deep minimum of the cross-correlation coefficient delineates the transition region between snow and rain in the horizontal direction if sufficiently large snowflakes are generated in the transition area. Otherwise, a sharp change of ZDR can be used to localize the position of the snow–rain line.

Corresponding author address: Dr. Alexander V. Ryzhkov, CIMMS, NOAA/NSSL, 1313 Halley Circle, Norman, OK 73069.

Abstract

Polarimetric signatures of snow precipitation for six Oklahoma snowstorms are examined. The available data consist of specific differential phase KDP, differential reflectivity ZDR, cross-correlation coefficient ρhv, and radar reflectivity factor Z. These data were obtained with the 10-cm-wavelength Cimarron polarimetric weather radar. The data suggest that in pure snow the average values of KDP and ZDR do not follow a systematic trend with change of the radar reflectivity factor if Z < 35 dBZ; this is not the case in rain. Precipitation is qualified as snow if the average ZDR is less than 0.2 dB for Z < 35 dBZ. The presence of a bright band with a pronounced ρhv minimum and ZDR maximum is a good discernible feature for discriminating between snow and rain. Thus, a localized deep minimum of the cross-correlation coefficient delineates the transition region between snow and rain in the horizontal direction if sufficiently large snowflakes are generated in the transition area. Otherwise, a sharp change of ZDR can be used to localize the position of the snow–rain line.

Corresponding author address: Dr. Alexander V. Ryzhkov, CIMMS, NOAA/NSSL, 1313 Halley Circle, Norman, OK 73069.

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Journal of Applied Meteorology and Climatology

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