CloudNET Radar Retrieval: Error Analysis & Method Advancements

1. The RadOn method and associated error analysisDelanoë J., Protat A., Bouniol D., Testud J. Centred’étude desEnvironnements Terrestre etPlanétairesCloudNET meeting : Paris 4/5th April 2005 Julien Delanoë

2. Outline • RadarOnly Algorithm • Error analysis • Retrieval

3. Radar Only AlgorithmRadOn Principle of the radar retrieval method

4. Z Doppler Velocity Vd=Vt+w  Density law and Area diameter relationships Dm(Vt) IWC, a, re , t N0*=f(Dm,Z) Principle of theRadar Algorithm (1) Vt retrieval

5. First step : Retrieval of VT from VD Vd=w+Vt Hypothesis (*) : for a long enough time span • 2 methods: • Vt-Z : Statistical relationship between Vd and Z • Assuming (*), we obtain Vt from Z (Vt=aZb) • New approach • Running Window: • Every 30s we compute the mean Vd over ±10 minutes (like Matrosov) for each radar gate.

6. Running Window (20min) • Advantages: • Better resolution than Matrosov method • More variability of Vt than Vt-Z • But instability of RadOn when Vt<5cm.s-1 Retrieval of terminal fall velocity with different methods 04/14/03 Palaiseau Vt from Vt-Z relationship

7. Vt retrieval Z Doppler Velocity Vd=Vt+w Density and Area diameter relationships Dm(Vt) IWC, a, re , t N0*=f(Dm,Z) Principle of theRadar Algorithm (2)

8. Principle of the radar retrieval method (2) Second step : estimate of the particle density r(D) and areaA(D)from VT-Z relationship • Vt-Z relationship obtained from radar is compared to microphysical Vt-Z relationships with different density and area laws. • Microphysical Vt-Z relationships : r(D)=arDbr and v(D)=f(m(D),A(D),ad,bd) (Mitchell 1996) Where m(D)=(p/6) ar D3+br, A=g Dsand ad, bd are the continuous drag coefficients (Khvorostianov and Curry 2002). From coefficients of Vt-Z radar relationship we estimate the best density diameter and area diameter relationships.

9. Example : 04/14/2003 Palaiseau • black: Vt-Z obtained by the radar • red: The best density and Area relationships

10. Vt retrieval Z Doppler Velocity Vd=Vt+w  Density and Area diameter relationships Dm(Vt) IWC, a, re , t N0*=f(Dm,Z) Principle of theRadar Algorithm (3) Step unchanged (see Delft presentation)

11. Vt retrieval Z Doppler Velocity Vd=Vt+w  Density law and Area diameter relationships Dm(Vt) IWC, a, re , t N0*=f(Dm,Z) Principle of theRadar Algorithm (4) Step unchanged (see Delft presentation) Direct relationship:

12. Vt retrieval Z Doppler Velocity Vd=Vt+w  Density and Area diameter relationships Dm(Vt) IWC, a, re , t N0*=f(Dm,Z) Principle of theRadar Algorithm (5)

13. Clouds parameters Using Dm N0* and Gamma shape => Clouds parameters

14. Evaluation of RadOn using the microphysical database

15. Evaluation of RadOn using the microphysical database We compute Vt,Z, IWC, a and re from the in-situ measurements, assuming A(D) and r(D) • Dataset: CLARE 98, CARL 99, EUCREX, ARM SGP, FASTEX, CEPEX, CRYSTALFACE • We impose a density law and area diameter relationships for a radar at 35 and 95GHz: A(D)=gDs with several couples of coefficients r(D)=aDb with several couples of coefficients Entries of the algorithm :Vt and Ze from in situ data RadOn Algorithm IWC,a, re microf IWC,a, re from RadOn

16. bias + std bias bias - std 5 « Area diameter relationships» 4 « Density diameter relationships »: b=-1.4, -1.1, -0.8, -0.5

17. bias + std bias bias - std

18. bias + std bias bias - std

19. RadOn Retrieval: • 14th April 2003: Palaiseau • Deep ice cloud • 15th April 2003: Palaiseau • Cirrus case

20. Retrieval 14th April 2003 N0* IWC r(D)=0.022D-0.6 A(D)=p/4D2 re a

21. r(D)=0.0005D-1.3 A(D)=0.05D1.4 N0* IWC Retrieval 15th April 2003 re a

22. Future work • Refine the error analysis • Run Radon on all the CloudNET sites, for all frequencies • Statistical study of density, IWC, a, re…. • Comparison with Radar/Lidar and other Radar algorithm

23. IWC retrieval from different method • RadOn with running window • RadOn with Vt-Z • IWC-Z-T R.J Hogan • IWC-Z Protat et al.

24. 1 2 With running window Vt-Z 3 4 IWC-Z-T RJH IWC-Z Protat et al.