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Comparing various Lidar/Radar inversion strategies using Raman Lidar data (part II)

Comparing various Lidar/Radar inversion strategies using Raman Lidar data (part II). D.Donovan, G-J Zadelhof (KNMI) Z. Wang (NASA/GSFC) D. Whiteman (NASA/GSFC). Introduction. Background/Rational Raman-vs-Elastic backscatter lidars Results Summary. Lidar. Time or Range. Radar. Lidar.

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Comparing various Lidar/Radar inversion strategies using Raman Lidar data (part II)

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  1. Comparing various Lidar/Radar inversion strategies using Raman Lidar data (part II) D.Donovan, G-J Zadelhof (KNMI) Z. Wang (NASA/GSFC) D. Whiteman (NASA/GSFC)

  2. Introduction • Background/Rational • Raman-vs-Elastic backscatter lidars • Results • Summary Cnet October Delft

  3. Lidar Time or Range Radar Lidar Returned Power Active (lidar/radar) cloud remote sensing Radar Lidar l= 3-100mm l= 350-1100nm Difference in returns is a function of particle size !! Cnet October Delft

  4. Rational • KNMI lidar/radar routine developed for simple elastic lR backscatter lidar. No Rayleigh return • MPL lidar data from ARM and SIRTA data has good Rayleigh signal. Should exploit it ! • Good Raman lidar data can serve as semi-independent test of the strengths and weakness of different approaches. • Will first concentrate on Visible extinction retrieval. Cnet October Delft

  5. Elastic vs Inelastic scattering Cnet October Delft

  6. Cnet October Delft

  7. No Rayleigh, No Raman The lidar extinction must first be extracted from the lidar signal (or, equivalently, the observed lidar backscatter must be corrected for attenuation). Observed signal Backscatter Calibration Constant Extinction Ze used to link backscatter and extinction and facilitate extinction correction/determination process. The retrieved extinction (corrected backscatter) can then be used with the Ze profile to estimate an effective particle size. Cnet October Delft

  8. No Rayleigh No Raman Must use Klett (Fernald + Rayleigh) Must estimate extinction at zm(cloud top) Very difficult to do directly if one only has lidar info If have Radar then use smoothness constraint on derived lidar/radar particle size, or extinction, or No*. But solutions converge if optical depth is above 1 or so !! Cnet October Delft

  9. If we have Useful Rayleigh above the cloud. Then (effectively) can find S and Clid so that The scattering ratio R is 1.0 below and above cloud Cnet October Delft

  10. If We have good Raman data then… Direct but noisy Less noisy but indirect Cnet October Delft

  11. Implementation Cost = Eo + W1*E1 +W2* E2 +W3*E3 + W4*E4 Eo  S-S’ E1 Force R=1 where no cloud. E2 Minimize derivative of R’eff E3Minimize derivative of ext E4Minimize derivative of No* Cnet October Delft

  12. A Test Case Using GSFC Raman lidar data and ARM MMCR. Cnet October Delft

  13. Signature of MS Comparison Using Rayleigh return above cloud Using smooth Reff (/Ze) constraint Cnet October Delft

  14. Raman Direct Raman Ratio Method 1:Use Rayleigh Method 2: Smooth /Ze Cnet October Delft

  15. Raman Direct Raman Ratio Method 1:Use Rayleigh Method 2: Smooth /Ze Cnet October Delft

  16. Raman Ratio-vs-Direct Cnet October Delft

  17. Cnet October Delft

  18. Cnet October Delft

  19. Combine Methods 1+2(4) ! Should work well in thicker Clouds also. Cnet October Delft

  20. Combine Methods 1+4 (or 2) ! Should work well in thicker Clouds also. 4 Cnet October Delft

  21. Ext –vs- Ze Cnet October Delft

  22. Multiple scattering effects clearly seen. Appear well accounted for using Eloranta’s approach. • Should use Rayleigh info if available ! • Aim to create blended approach for non-Raman lidars to smoothly handle range of cases for non-Raman (i.e MPL) where Rayleigh signal from above cloud may or may not be available (almost there). • Inferring optical depth using Ze alone very tricky on a case-by-case basis. • Needs robust cloud masking (cld/nocloud/no info) Conclusions Cnet October Delft

  23. Cnet October Delft

  24. Combine Methods 1+4 (or 2) ! Should work well in thicker Clouds also. Cnet October Delft

  25. Method 1: Ray above Raman Ratio Raman Direct Raman Ratio-vs-Direct Method 2: Smooth /Ze Raman Ratio Raman Direct (Raman direct) Cnet October Delft

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