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Applications of polarimetric radar data in NWP

Applications of polarimetric radar data in NWP. 10/18/2011 Youngsun Jung CAPS/OU. Capability of polarimetric radar data (PRD). Hydrometeor classification Quantitative rain estimation Radar data quality control Verification of numerical weather forecast

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Applications of polarimetric radar data in NWP

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  1. Applications of polarimetric radar data in NWP 10/18/2011 Youngsun Jung CAPS/OU

  2. Capability of polarimetric radar data (PRD) • Hydrometeor classification • Quantitative rain estimation • Radar data quality control • Verification of numerical weather forecast • Improvement in microphysical parameterization • Data assimilation

  3. Capability of polarimetric radar data (PRD) • Hydrometeor classification • Quantitative rain estimation • Radar data quality control • Verification of numerical weather forecast • Improvement in microphysical parameterization • Data assimilation

  4. Understanding PRD • PRD contains information on size, shape, orientation, and phase composition of particles. • If the model microphysics scheme is unable to properly handle these kinds of information, information carried by PRD can easily mislead users. • Particle shape: not (explicitly) assumed • Orientation: not assumed • Size distribution: Gamma DSD • Phase: each phase is independent of others (exceptions: Ferrier and Ziegler schemes?)

  5. Understanding PRD • PRD simulator should take account of DSD, shape, orientation and phase of particles. • Non-meteorological effects that cannot be simulated by the model can significantly influence polarimetric signatures. • PR variables has their own weaknesses. • KDP field is often very noisy in weak rain regions and is vulnerable to errors. • Polarimetric signatures are very weak at high altitudes where the hydrometeors are mostly ice particles.

  6. Polarimetric signature

  7. Verification using PRD KVNX KTLX

  8. Verification using PRD KOUN

  9. Drop size distribution: Number of drops Number of drops SM DM Size Size • Drop growth (shrinking) during accretion or diffusion (evaporation) while keeping the number concentration constant • Number concentration changes during aggregation or breakup while the total mass remains constant • Size sorting due to differential sedimentation Jung, Xue, Zhang, 2010: Simulations of polarimetric signatures of a supercell storm using a two-moment bulk microphysics scheme. J. Appl. Meteorol. Clim., 49, 146-163

  10. KOUN observations and simulated polarimetric variables at .5° tilt at 0200 UTC SM DM OBS Obs Z(dBZ) ZDR(dB) KDP(° km-1) ρhv ice By Bryan Putnam

  11. What do we need to use PRD? • Well-calibrated and QC-ed observations • Accurate forward observation operator • Two- or higher-moment microphysics scheme • Improved formulations of microphysical processes in the bulk microphysics scheme

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