1. Stefan Kneifel, Pavlos Kollias - McGill Frederic Tridon – Univ. Leicester Ed Luke - BNL

4. Scattering with the K a -W band combination – Rayleigh conditions not satisfied as a whole – But, smallest drops scatter in the Rayleigh regime  their contribution on the DWR depends on differential attenuation only Doppler spectra ratio (DSR) – Drops sorted according to their fall velocity and size with V t =f(D) (Atlas et al., 1973) – The DSR emphasizes the two scattering regimes Rayleigh regime plateau Mie region (with two peaks) Quasi universal pattern

5. 15/09/2011: homogeneous light rain  DSR shape agree well with theory  possible to disentangle the Mie and attenuation effects (Tridon et al. (2013), Geophys. Res. Lett., 40)  But some spectra issues prevent this method with the KASACR data (while its volume better match the measurements of the WSACR) and on more inhomogeneous cases Presentation of the DSR technique during MC3E session on Monday Confirmation with KAZR and WSACR data

6.  (Back-)scattering depends on particle size/mass, habit and frequency Ku (13.4 GHz) Ka (36.5 GHz) W (89 GHz) ‚Soft‘ spheres ‚Soft‘ ellipsoids

7. Theoretical triple frequency signatures indicate habit-related signatures… Observed triple frequency signatures in Wakasa Bay aircraft data by Kulie et al., JAMC, 2013 Aggregates?? Graupel??

8. NSA, 12.Feb.2012, 08:52 UTC KaZR-spectrum: black WSaCR-spectrum: yellow Frequency independent Rayleigh scattering region (plateau in spectral DWR) Mie scattering region

10. WSACR narrow Nyquist velocity Case KASACRWSACR V Nyq [m/s]Pulse [m]V Nyq [m/s]Pulse [m] 10/06/2011± 10455± 7.245 16/09/2011± 10455± 7.245 17-18/09/2011± 10455± 7.245 11/12/2011± 10200± 450 08/03/2012± 10263± 4240 08/07/2012± 10263± 4240 05/08/2012± 101350± 4240 14/08/2012± 101350± 4240 18/08/2012± 101350± 4240 24/08/2012± 101350± 4240 25/08/2012± 101350± 4240 25-26/08/2012± 101350± 4240 13-14/09/2012± 101350± 4240 12/10/2012± 101350± 4240 15/12/2012± 101350± 4240 Rain spectra can extend over more than 8 m/s width  a Nyquist velocity of ± 4 is insufficient Need wider Nyquist velocity in rain but narrower in ice (cloud and snow)  temperature dependant modes?

11. 2600m 1500m 800m kazr-kasacr comparison Range and time kasacr spectrograms Spurious bulges appear at the sides of kasacr spectra where there should be only noise (kazr) 15 Sep 2011 19:32 to 19:58 KASACR spectra artefact

12. WSACR and KaSACR: Very accurate beam matching, similar beam widths, average times, range resolution, … NSA WSACR and KaSACR: Spectra from ice clouds show very different spectral width. Time sampling and averaging should be exactly the same; also same range resolution NSA - KaSACR NSA - WSACR NSA, 11.07.2013

14. NSA - WSACR NSA - KaZR KaZR shows interesting secondary peak – no spectral sidelobes! The multiple artifacts in the WSACR makes it impossible to distinguish artifacts from microphysical signals! It also affects estimation of radar moments (e.g. skewness, kurtosis, etc) Similar artifacts found in the SGP SACRS (but different strength and not all time periods) and PVC WACR. Can this be solved/avoided somehow? NSA, 14.01.2013

15. Importance of matching in range For best results, the volume should be exactly matched in range i.e. with the same volume centres and sizes (pulse width and range weighting function when pulse coding) DSR: KASACR-WSACR DSR: KAZR-WSACR Closest gate Only 5 m shift!

16. Importance of matching in range Otherwise some interpolation can alleviate the mismatch but not completely in case of inhomogeneous volume Weighted interpolation between the two closest gates KASACR-WSACR KAZR-WSACR

18.  First spectrum analysis clearly indicates that multi-frequency spectra contain wealth of information about cloud and precipitation microphysics.  However, requirements for spectral analysis are very demanding:  „Perfectly“ vertically matched radar volumes -> same pulse width, same range gates, same range weighting function  „Perfect“ beam alignment  Possibility of variable Nyquist range for rain and ice/snow clouds  Similar or same velocity resolution for spectra (at least for both SACR)  Same temporal averaging/sampling  Radar calibration Sanity check: Ice clouds -> Multi-frequency spectra MUST match (small ice = Rayleigh scatterers)

19. SGP - KaZRSGP - KaSACRSGP - WSACR KaZR: 0.3 m/s KaSACR: 0.7 m/s WSACR: 0.7-0.8 m/s SGP, 20.04.2013

20. Collecting Off-zenith SACR Spectra During Scanning Motivation  Enhanced perspective on cloud process evolution  Increased opportunity for data QC  Reduction of large time-gaps lacking spectra (esp. at W band)  Availability of controlled off-zenith data will drive innovation  Offers a controlled development test-bed for moving platforms Approach  Start small (e.g. with IOP)  Collect occasional full RHI scans  Can radar be modified to always save spectra for theta <  ?

21. Observing Microphysics with Off-zenith Spectra ref_pri mdv_pri sw_pri skew_pri, kurt_pri, snr_pri, lslope_pri, rslope_pri ref_sec mdv_sec sw_sec skew_sec, kurt_sec, snr_sec, lslope_sec, rslope_sec v_leftpeak_pri, dynr_leftpeak_pri v_rightpeak_pri, dynr_rightpeak_pri dynr_pri, Vpeak_pri dynr_sec, Vpeak_sec vmin_secvmin_privmax_privmax_sec noise npeaks_pri A 256-bin Doppler spectrum experiences shape distortion of less than 1 bin induced by pointing angles up to 7 degrees off zenith.

22. Observing Microphysics with Off-zenith Spectra Non motion-compensated spectrum skewness during MAGIC

23. First IOP at NSA site with focus on ice clouds and snowfall: – Find out which settings are optimum (time, range resolution, etc.) in order to investigate the various processes (nucleation, aggregation, riming, etc.)? – How good can we get the spectra matching in the Rayleigh part of the spectrum from KaZR, KaSACR, WSACR if we run them simultaneousely and with similar settings (range, time res., zenith looking)? – What are benefits/disadvantages of pulse compression regarding spectra? Additional snowfall specific experiments within IOP: – Perform slow RHI scans with KaSACR/WSACR and XSAPR in the same vertical plane to obtain triple frequency signatures – Compare triple frequency signatures to novel in-situ data (3D snowflake camera MASC) -> Are the trip.-freq. signatures really so strongly related to snowfall habit?

26. NSA - KaZR NSA - WSACR Number and strength of „side lobes“ increase with magnitude of real signal; first artifacts at ca. -15 dBZ for KaSACR and ca. -11 dBZ for WSACR

27. Despite the different range resolution (25 m vs 30 m), the spectra in the ice part are matching extremely well. NSA - KaZR NSA - WSACR NSA - KaZR NSA - WSACR

28. In the snowfall part (900 m), the WSACR seems to be shifted by 0.1-0.2 m/s towards larger fall velocities (or KaZR is too slow…?) – Note the shift is independent of the velocity regime -> no Mie scattering effect! NSA - KaZR NSA - WSACR NSA - KaZR NSA - WSACR

29. + + + Need well-matched beams to avoid artefacts Light stratiform rain with higher Z fall-streak  zoom to avoid BB and low SNR due to wind shear Dual wavelength ratio – increase with height because of rain and gas attenuation – except right above the fall- streak  possible with important Mie effect in the fall-streak due to larger drops Check by looking at spectra

30. Confirmation with KAZR and WSACR data KAZRWSACRKAZR-WSACR