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Abstract Polarimetric radar data from the WSR-88D network are used to examine the evolution of various polarimetric precursor signatures to tornado dissipation within a sample of 36 supercell storms. These signatures include an increase in bulk hook echo median raindrop size, a decrease in midlevel differential radar reflectivity factor (ZDR) column area, a decrease in the magnitude of theZDRarc, an increase in the area of low-level large hail, and a decrease in the orientation angle of the vector separating low-levelZDRand specific differential phase (KDP) maxima. Only supercells that produced “long-duration” tornadoes (with at least four consecutive volumes of WSR-88D data) are investigated, so that signatures can be sufficiently tracked in time, and novel algorithms are used to isolate each storm-scale process. During the time leading up to tornado dissipation, we find that hook echo median drop size (D0) and medianZDRremain relatively constant, but hook echo medianKDPand estimated number concentration (NT) increase. TheZDRarc maximum magnitude andZDR–KDPseparation orientation angles are observed to decrease in most dissipation cases. Neither the area of large hail nor theZDRcolumn area exhibit strong signals leading up to tornado dissipation. Finally, combinations of storm-scale behaviors and TVS behaviors occur most frequently just prior to tornado dissipation, but also are common 15–20 min prior to dissipation. The results from this study provide evidence that nowcasting tornado dissipation using dual-polarization radar may be possible when combined with TVS monitoring, subject to important caveats.
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Improving Estimation of Specific Differential Phase and Assessing Differential Backscattering Phase
Abstract Polarimetric variables such as differential phase ΦDPand its range derivative, specific differential phaseKDP, contain useful information for improving quantitative precipitation estimation (QPE) and microphysics retrieval. However, the usefulness of the current operationally utilized estimation method ofKDPis limited by measurement error and artifacts resulting from the differential backscattering phaseδ. The contribution ofδcan significantly influence the ΦDPmeasurements and therefore negatively affect theKDPestimates. Neglecting the presence ofδwithin non-Rayleigh scattering regimes has also led to the adoption of incorrect terminology regarding signatures seen within current operationalKDPestimates implying associated regions of unrealistic liquid water content. A new processing method is proposed and developed to estimate bothKDPandδusing classification and linear programming (LP) to reduce bias inKDPestimates caused by theδcomponent. It is shown that by applying the LP technique specifically to the rain regions of Rayleigh scattering along a radial profile, accurate estimates of differential propagation phase, specific differential phase, and differential backscattering phase can be retrieved within regions of both Rayleigh and non-Rayleigh scattering. This new estimation method is applied to cases of reported hail and tornado debris, and the LP results are compared to the operationally utilized least squares fit (LSF) estimates. The results show the potential use of the differential backscattering phase signature in the detection of hail and tornado debris.
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- Award ID(s):
- 2136161
- PAR ID:
- 10522789
- Publisher / Repository:
- American Meteorological Society
- Date Published:
- Journal Name:
- Journal of Applied Meteorology and Climatology
- Volume:
- 63
- Issue:
- 7
- ISSN:
- 1558-8424
- Format(s):
- Medium: X Size: p. 803-819
- Size(s):
- p. 803-819
- Sponsoring Org:
- National Science Foundation
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