The RadOn method and associated error analysisDelano J., Protat A., Bouniol D., Testud J.
Centre dtude des Environnements Terrestre et Plantaires
CloudNET meeting : ParisJulien Delano4/5th April 2005
Outline
RadarOnly Algorithm
Error analysis
Retrieval
Radar Only Algorithm
RadOn Principle of the radar retrieval method
Principle of the Radar Algorithm (1)Vt retrieval
First step : Retrieval of VT from VD Vd=w+VtHypothesis (*) : for a long enough time span2 methods:Vt-Z : Statistical relationship between Vd and ZAssuming (*), we obtain Vt from Z (Vt=aZb)
New approachRunning Window: Every 30s we compute the mean Vd over 10 minutes (like Matrosov) for each radar gate.
Vt from Vt-Z relationship 04/14/03 PalaiseauRetrieval of terminal fall velocity with different methods
Principle of the Radar Algorithm (2)
Principle of the radar retrieval method (2)Second step : estimate of the particle density r(D) and area A(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 Ds and 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.
Example : 04/14/2003 Palaiseaublack: Vt-Z obtained by the radarred: The best density and Area relationships
Principle of the Radar Algorithm (3)Step unchanged (see Delft presentation)
Principle of the Radar Algorithm (4)Step unchanged (see Delft presentation)Direct relationship:
Principle of the Radar Algorithm (5)
Clouds parametersUsing Dm N0* and Gamma shape => Clouds parameters
Evaluation of RadOn using the microphysical database
Evaluation of RadOn using the microphysical databaseDataset: 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
We compute Vt, Z, IWC, a and re from the in-situ measurements, assuming A(D) and r(D) RadOn AlgorithmIWC, a, re from RadOnIWC, a, re microfEntries of the algorithm :Vt and Ze from in situ data
biasbias + stdbias - std4 Density diameter relationships : b=-1.4, -1.1, -0.8, -0.55 Area diameter relationships
biasbias + stdbias - std
biasbias + stdbias - std
RadOn Retrieval:14th April 2003: PalaiseauDeep ice cloud15th April 2003: PalaiseauCirrus case
Retrieval 14th April 2003IWCreN0*ar(D)=0.022D-0.6A(D)=p/4D2
Retrieval 15th April 2003IWCreN0*ar(D)=0.0005D-1.3A(D)=0.05D1.4
Future workRefine 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
IWC retrieval from different methodRadOn with running window
RadOn with Vt-Z
IWC-Z-T R.J Hogan
IWC-Z Protat et al.
With running windowVt-ZIWC-Z-T RJHIWC-Z Protat et al.1234
