A Technique to Measure Entrainment in Cloud by Dual-Polarization Radar and Chaff
- 1 March 1987
- journal article
- Published by American Meteorological Society in Journal of Atmospheric and Oceanic Technology
- Vol. 4 (1) , 75-83
- https://doi.org/10.1175/1520-0426(1987)004<0075:attmei>2.0.co;2
Abstract
A new method for studying the entrainment of air into clouds has been developed and tested, and initial results demonstrating the technique are presented here. This new method is superior to other chaff techniques that allow air parcels to be followed only until the chaff reflectivity becomes indistinguishable from cloud reflectivity. Frequently this is won after the chaff enters the cloud. The new technique uses circular depolarization ratio (CDR) measurements to avoid this limitation. Since the CDR of chaff is typically 20 dB greater than that of most hydrormeteors, the signature provided by CDR allows chaff to be followed into moderately reflective regions of the cloud long after the reflectivity signature of the chaff has disappeared. Circular polarization is superior to linear polarization in measurements such as these because the chaff signatures in circular depolarization do not require assumptions about chaff filament orientation, whereas interpretation of ZDR signatures (from linear pola... Abstract A new method for studying the entrainment of air into clouds has been developed and tested, and initial results demonstrating the technique are presented here. This new method is superior to other chaff techniques that allow air parcels to be followed only until the chaff reflectivity becomes indistinguishable from cloud reflectivity. Frequently this is won after the chaff enters the cloud. The new technique uses circular depolarization ratio (CDR) measurements to avoid this limitation. Since the CDR of chaff is typically 20 dB greater than that of most hydrormeteors, the signature provided by CDR allows chaff to be followed into moderately reflective regions of the cloud long after the reflectivity signature of the chaff has disappeared. Circular polarization is superior to linear polarization in measurements such as these because the chaff signatures in circular depolarization do not require assumptions about chaff filament orientation, whereas interpretation of ZDR signatures (from linear pola...Keywords
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