Upload
dorian-dodson
View
33
Download
0
Tags:
Embed Size (px)
DESCRIPTION
The RadOn method and associated error analysis Delanoë J., Protat A., Bouniol D., Testud J. C entre d’étude des E nvironnements T errestre et P lanétaires CloudNET meeting : Paris. 4/5 th April 2005. Julien Delanoë. Outline. Rad ar On ly Algorithm Error analysis Retrieval. - PowerPoint PPT Presentation
Citation preview
11
The RadOn method and associated error analysis
Delanoë J., Protat A., Bouniol D., Testud J.
Centre d’étude des Environnements Terrestre et Planétaires
CloudNET meeting : Paris
Julien Delanoë4/5th April 2005
44
Principle of the Radar Algorithm (1)
Z Doppler VelocityVd=Vt+w
Density law and Area diameter relationships
Dm(Vt)
N0*=f(Dm,Z) IWC, , re
Vt retrieval
55
First step : Retrieval of VT from VD
Vd=w+Vt
Hypothesis (*) : for a long enough time span tw V
2 methods:•Vt-Z : Statistical relationship between Vd and ZAssuming (*), 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.
66
Running Window (20min)
Advantages:•Better resolution than Matrosov method•More variability of Vt than Vt-ZBut instability of RadOn when Vt<5cm.s-1
Vt from Vt-Z relationship
04/14/03 Palaiseau
Retrieval of terminal fall velocity with different methods
77
Principle of the Radar Algorithm (2)
Z Doppler VelocityVd=Vt+w
Density and Area diameter relationships
Dm(Vt)
N0*=f(Dm,Z) IWC, , re
Vt retrieval
88
Principle of the radar retrieval method (2)Second step : estimate of the particle density (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 : (D)=aDb and v(D)=f(m(D),A(D),ad,bd) (Mitchell 1996) Where m(D)=(/6) a D3+b , A= D 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.
99
Example : 04/14/2003 Palaiseau
•black: Vt-Z obtained by the radar•red: The best density and Area relationships
1010
Principle of the Radar Algorithm (3)
Z Doppler VelocityVd=Vt+w
Density and Area diameter relationships
Dm(Vt)
N0*=f(Dm,Z) IWC, , re
Vt retrieval
Step unchanged (see Delft presentation)
1111
Principle of the Radar Algorithm (4)
Z Doppler VelocityVd=Vt+w
Density law and Area diameter relationships
Dm(Vt)
N0*=f(Dm,Z) IWC, , re
Vt retrieval
Step unchanged (see Delft presentation)Direct relationship:
25 18 1
*0 4
10( / )e m bsc
wN Z F D D dD
K
1212
Principle of the Radar Algorithm (5)
Z Doppler VelocityVd=Vt+w
Density and Area diameter relationships
Dm(Vt)
N0*=f(Dm,Z) IWC, , re
Vt retrieval
1313
Clouds parameters
max
min
( )z
zs ds
3 *0210 ( / )mN F D D D dD
* 4044
wmIWC N D
3
2e
IWCr
Using Dm N0* and Gamma shape => Clouds parameters
1515
Evaluation of RadOn using the microphysical database
• 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)=D with several couples of coefficients
(D)=aDb with several couples of coefficients
We compute Vt, Z, IWC, and re from the in-situ measurements, assuming A(D) and
(D)
RadOn Algorithm
IWC, , re from RadOnIWC, , re micro
Entries of the algorithm :Vt and Ze from in situ data
1616
bias
bias + std
bias - std
4 « Density diameter relationships »: b=-1.4, -1.1, -0.8, -0.5
5 « Area diameter relationships»
1919
RadOn Retrieval:
•14th April 2003: PalaiseauDeep ice cloud•15th April 2003: PalaiseauCirrus case
2222
Future work
• Refine the error analysis
• Run Radon on all the CloudNET sites, for all frequencies
• Statistical study of density, IWC, , re….
• Comparison with Radar/Lidar and other Radar algorithm
2323
IWC retrieval from different method
1. RadOn with running window
2. RadOn with Vt-Z
3. IWC-Z-T R.J Hogan
4. IWC-Z Protat et al.