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【正文】 of noise ?Filtering or smoothing the range profile of Ψdp ?Linear regression fit to the range profile of Ψdp Elimination of nonhydrometeor radar echo ?Statement of the problem: For hydrometeorological applications, it is desirable to isolate hydrometeors (., cloud and precipitation particles) from nonhydrometeors (., ground clutter and socalled “clearair” returns, which is actually insects and sometimes birds). ?Nonpolarimetric radar techniques –Analyze elevation (or height) variation in echo structure. ?Problems with shallow systems ?Subjective –Create a “clutter mask” by statistically characterizing ground clutter at a site using long periods of nonraining data. ?Does not account for anomalous propagation. –Doppler clutter filters typically eliminate radar echo with nonzero Doppler velocity and/or nearzero Doppler spectrum width. ?Works reasonably well but can eliminate precipitation echo. Where’s the ground clutter? Where’s the ground clutter? Elimination of nonhydrometeor echo: Polarimetric radar technique Applying ρhv threshold Elimination of nonhydrometeor echo: Polarimetric radar technique Simple Suppression of Ground Clutter Using Polarimetric Radar Techniques 23 July 02 Npol DZ (unedited) (2022 UTC) 23 July 02 Npol DZ (edited) (2022 UTC) ? Thresholds: ρhv , σ(Ψdp) 18176。 Summary for Nonhydrometeor Rejection by Polarimetric Methods Estimation of Specific Differential Phase (Kdp) Range Filtering: Method 1 Example of Differential Propagation Phase (φdp)and Specific Differential Phase (Kdp) Estimation in rain at Cband ( cm) Linear Regression: Method 2 Standard Deviation of Kdp for method 2
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