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Dual-Polarization and Dual-Wavelength Radar Measurements

Dual-Polarization and Dual-Wavelength Radar Measurements. Vivek National Center for Atmospheric Research Boulder, Colorado. Polarization and dual-wavelength radar Cloud microphysics III. Examples of products and ka-band observations. Dual-wavelength radar: S-Polka. Microphysics.

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Dual-Polarization and Dual-Wavelength Radar Measurements

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  1. Dual-Polarization and Dual-Wavelength Radar Measurements Vivek National Center for Atmospheric Research Boulder, Colorado • Polarization and dual-wavelength radar • Cloud microphysics • III. Examples of products and ka-band observations.

  2. Dual-wavelength radar: S-Polka

  3. Microphysics • Precipitation type: Ice or liquid? • Precipitation particle shape, size and concentration. • Sensitivity: -10 dBZ @ 50 km • 0.1 mm droplet size100 per liter

  4. Spatial distribution of polarization radar measurements, retrievedDSD parameters, and rain rate Reflectivity ZDR . ( Number concentration # m^-3 Shape of DSD Median volume Diameter, mm Rain rate mm/hr

  5. Examples of Ka-band radar Measurements

  6. Sample Plane Parallel Indicator (PPI) Scan From WISP04, 2004.

  7. Range Height Indicator from WISP04 Height (km) Range (km) S-Band Reflectivity (dBZ) Ka-Band Reflectivity (dBZ) Pristine Crystals Dry snow Side lobe artifact Ground clutter Irregular crystals Z difference (S-band – Ka-band) Particle ID output

  8. Advantages of dual-wavelength system • Detection of cloud droplets. • Estimate of size and LWC. • Raindrop size distribution . • Effect of Bragg scatter is less at Ka-band. • Improved cloud microphysical retrieval using both dual-wavelength and dual-polarization observations.

  9. Knight et al. JAS, J. Atmos. Sci., 59, 1454-1472. Data from the RHIs are fit to a Gamma distribution and characteristics of the drops are displayed here as labeled at the left at the three times for the three rows. The last row, m, is an exponent in the gamma distribution. When m = 0 the distribution is exponential, and as m increases it narrows. The rainfall rate is calculated as if at the ground with zero vertical air velocity.

  10. Issues: Measurement • Number of independent samples and standard error of radar observables. • Calibration of radar measurements. • How to combine forward scattering observations with backscatter measurements?

  11. Issues: Microphysics • Drop shape and size distribution (DSD). • Ice particle shape and density. • How to separate DSD and particle shape effects in polarization measurements? • How to detect super cooled droplets?

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