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Measuring rainwater content by radar using propagation differential phase shiftWhile radars measure several quantities closely coupled to the rainfall rate, for frequencies less than 15 GHz, estimates of the rainwater content W are traditionally computed from the radar reflectivity factor Z or the rate of attenuation A--quantities only weakly related to W. Consequently, instantaneous point estimates of W using Z and A are often erroneous. A more natural, alternative parameter for estimating W at these frequencies is the specific polarization propagation differential phase shift phi(sub DP), which is a measure of the change in the difference between phases of vertically (V) and horizontally (H) polarized waves with increasing distance from a radar. It is now well known that W is nearly linearly related to phi(sub DP) divided by (1 - reversed R), where reversed R is the mass-weighted mean axis ratio of the raindrops. Unfortunately, such relations are not widely used in part because measurements of phi(sub DP) are scarce but also because one must determine reversed R. In this work it is shown that this parameter can be estimated using the differential reflectivity (Z(sub H)/Z(sub V) at 3 GHz. An alternative technique is suggested for higher frequencies when the differential reflectivity becomes degraded by attenuation. While theory indicates that it should be possible using phi(sub DP) to estimate W quite accurately, measurement errors increase the uncertainty to +/- 18%-35% depending on reversed R. While far from ideal, it appears that these estimates are likely to be considerably more accurate than those deduced using currently available methods.
Document ID
19950031653
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Jameson, A. R.
(Applied Research Corp. Landover, MD, United States)
Date Acquired
August 16, 2013
Publication Date
April 1, 1994
Publication Information
Publication: Journal of Atmospheric and Oceanic Technology
Volume: 11
Issue: 2 pt
ISSN: 0739-0572
Subject Category
Meteorology And Climatology
Accession Number
95A63252
Funding Number(s)
CONTRACT_GRANT: NSF ATM-90-15394
CONTRACT_GRANT: NAS5-30430
CONTRACT_GRANT: JPL-958437
Distribution Limits
Public
Copyright
Other

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