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

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Presentation on theme: "Stratus Cloud parameters retrieval from Doppler radar Virendra P. Ghate."— Presentation transcript:

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

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

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

4 Lognormal DSD x=log e (r) x 0 =log e (r 0 )

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

6 Moments are related DSD MomentDoppler Moment σ x =0.35 ???

7 Cloud Vs Drizzle

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9 Observations Atlantic Stratocumulus Transition Experiment (ASTEX) Atlantic Stratocumulus Transition Experiment (ASTEX) Porto Santo, Portugal; June 1992 Porto Santo, Portugal; June 1992 InstrumentProduct 35 GHz cloud Doppler radar Reflectivity, Doppler velocity, spectrum width 3 channel Radiometer Liquid Water path, Water vapor path

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. 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. 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. Potential for surface based remote sensors to do long-term monitoring.

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

16 SHEBA/FACE Surface Heat Budget of the Arctic Ocean Surface Heat Budget of the Arctic Ocean ; ; ; ; FIRE Arctic Cloud Experiment (FACE) FIRE Arctic Cloud Experiment (FACE) April – July 1998April – July 1998

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18 Instrumentation InstrumentCharacteristics Forward Scattering Spectrometer Probe (FSSP) 16 Channel, 2–47 µm, ~3 µm binwidth 1D Optical Array Probe (OAP) 64 Channel, µm, 10 µm binwidth

19 Data 18 July UTC to 19 July 0300 UTC 18 July UTC to 19 July 0300 UTC

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21 Calculated dBZ and V D

22 Frisch derived D 0 and N

23 DSD Comparison

24 Liquid Water Content

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

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