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Stratus Cloud parameters retrieval from Doppler radar

Stratus Cloud parameters retrieval from Doppler radar. Virendra P. Ghate. Outline. Introduction Radar spectra and DSD Model setup Observations & Results SHEBA data Model Observation comparisons Conclusion. Cloud Radar Spectra. Reflectivity dBZ=10*log 10 (Z) Doppler Velocity

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Stratus Cloud parameters retrieval from Doppler radar

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  1. Stratus Cloud parameters retrieval from Doppler radar Virendra P. Ghate

  2. Outline • Introduction • Radar spectra and DSD • Model setup • Observations & Results • SHEBA data • Model Observation comparisons • Conclusion

  3. Cloud Radar Spectra Reflectivity dBZ=10*log10(Z) Doppler Velocity Doppler Spectrum Width

  4. Lognormal DSD x=loge(r) x0=loge(r0)

  5. Known Reflectivity Doppler Velocity Doppler Spectrum width Unknown Total Number of Droplets Modal Radius Lognormal Width Parameters

  6. Moments are related DSD Moment Doppler Moment σx=0.35 ???

  7. Cloud Vs Drizzle

  8. Cloud Vs Drizzle

  9. Observations • Atlantic Stratocumulus Transition Experiment (ASTEX) • Porto Santo, Portugal; June 1992

  10. Observations on 6 June 1992 North comp East comp

  11. Retrievals

  12. LWC Retrieval

  13. Cooling Rate Retrieval

  14. Conclusions • Technique to derive cloud and drizzle DSD, LWC from first three Doppler moments. • Need to average long enough to compensate for turbulent vertical velocity, horizontal homogeneity etc. • Potential for surface based remote sensors to do long-term monitoring.

  15. Frisch Model Test Calculate Bulk Parameters Get Known DSD Compute radar Moments Apply Frisch Model

  16. SHEBA/FACE • Surface Heat Budget of the Arctic Ocean • 1995-1996; 1997-1999; 2000-2002 • FIRE Arctic Cloud Experiment (FACE) • April – July 1998

  17. Instrumentation

  18. Data • 18 July 1998 2230 UTC to 19 July 0300 UTC

  19. Calculated dBZ and VD

  20. Frisch derived D0 and N

  21. DSD Comparison

  22. Liquid Water Content

  23. Conclusions • Frisch technique can be applied to retrieve cloud/drizzle characteristics under Stratiform conditions. • The DSD obtained from the technique might not fit the observed, but the bulk parameter (LWC etc.) are reasonably retrieved.

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