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Differential propagation phase shift and rainfall rate estimation
Author(s) -
Sachidananda M.,
Zrnic D. S.
Publication year - 1986
Publication title -
radio science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.371
H-Index - 84
eISSN - 1944-799X
pISSN - 0048-6604
DOI - 10.1029/rs021i002p00235
Subject(s) - differential phase , mathematics , statistics , standard deviation , range (aeronautics) , standard error , sensitivity (control systems) , phase (matter) , physics , quantum mechanics , materials science , electronic engineering , engineering , composite material
This paper presents two methods for computing differential propagation phase shift (ϕ DP ) using time series data form a coherent radar with alternate switching between two linear but orthogonal polarizations. An analysis of the statistical error in ϕ DP estimate shows that ϕ DP can be estimated with less than 0.5° standard error using time and range averaging. To evaluate the usefulness of ϕ DP for estimating rainfall rate (R) vis‐a‐vis the Z DR method, a discussion on the sensitivity of R to standard errors in ϕ DP as well as Z H and Z DR is presented. It is shown that the relation, differential propagation phase constant Δϕ versus R , is relatively insensitive to drop size distribution (DSD) variations and thus can yield more accurate R estimate, even when a direct relationship between Δϕ and R is assumed. However, standard error in Δϕ estimate causes large inaccuracies of R at low values ( R < 50 mmh −1 ), thus limiting its usefulness to higher rainfall rates. It is also shown that Δϕ can be used as a third remote measurable in conjunction with Z H and Z DR to determine a three parameter gamma DSD. Another use of Δϕ is likely to be in hydrometeor type identification, especially hail in severe storms.