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Dual-Polarization and Dual-Wavelength Radar Measurements Vivek National Center for Atmospheric Research Boulder, Colorado I.Polarization and dual- wavelength.

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Presentation on theme: "Dual-Polarization and Dual-Wavelength Radar Measurements Vivek National Center for Atmospheric Research Boulder, Colorado I.Polarization and dual- wavelength."— Presentation transcript:

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

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3 Dual-wavelength radar: S-Polka

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

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

7 Examples of Ka-band radar Measurements

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

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

11 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.

12 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, , is an exponent in the gamma distribution. When  = 0 the distribution is exponential, and as  increases it narrows. The rainfall rate is calculated as if at the ground with zero vertical air velocity.

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14 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?

15 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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