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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 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*log10(Z) Doppler Velocity Doppler Spectrum Width
Lognormal DSD x=loge(r) x0=loge(r0)
Known Reflectivity Doppler Velocity Doppler Spectrum width Unknown Total Number of Droplets Modal Radius Lognormal Width Parameters
Moments are related DSD Moment Doppler Moment σx=0.35 ???
Observations • Atlantic Stratocumulus Transition Experiment (ASTEX) • Porto Santo, Portugal; June 1992
Observations on 6 June 1992 North comp East comp
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.
Frisch Model Test Calculate Bulk Parameters Get Known DSD Compute radar Moments Apply Frisch Model
SHEBA/FACE • Surface Heat Budget of the Arctic Ocean • 1995-1996; 1997-1999; 2000-2002 • FIRE Arctic Cloud Experiment (FACE) • April – July 1998
Data • 18 July 1998 2230 UTC to 19 July 0300 UTC
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.