The RadOn method and associated error analysis Delano

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The RadOn method and associated error
analysisDelanoë J., Protat A., Bouniol D.,
Testud J. Centre détude des Environnements
Terrestre et PlanétairesCloudNET meeting Paris
Julien Delanoë
4/5th April 2005
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Outline

• RadarOnly Algorithm
• Error analysis
• Retrieval

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Radar Only AlgorithmRadOn Principle of the
radar retrieval method
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Principle of the Radar Algorithm (1)
Vt retrieval
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• First step Retrieval of VT from VD
  VdwVt
• Hypothesis () for a long enough time span

• 2 methods
• Vt-Z Statistical relationship between Vd and Z
• Assuming (), we obtain Vt from Z (VtaZb)
• New approach
• Running Window
• Every 30s we compute the mean Vd over 10 minutes
  (like Matrosov) for each radar gate.

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Retrieval of terminal fall velocity with
different methods
04/14/03 Palaiseau
Vt from Vt-Z relationship
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Principle of the Radar Algorithm (2)
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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 D3br , Ag 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.

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Example 04/14/2003 Palaiseau

• black Vt-Z obtained by the radar
• red The best density and Area relationships

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Principle of the Radar Algorithm (3)
Step unchanged (see Delft presentation)
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Principle of the Radar Algorithm (4)
Step unchanged (see Delft presentation) Direct
relationship
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Principle of the Radar Algorithm (5)
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Clouds parameters
Using Dm N0 and Gamma shape gt Clouds parameters
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Evaluation of RadOn using the microphysical
database
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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)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)
Entries of the algorithm Vt and Ze from in situ
data
RadOn Algorithm
IWC, a, re from RadOn
IWC, a, re microf
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bias std
bias
bias - std
5 Area diameter relationships
4 Density diameter relationships b-1.4,
-1.1, -0.8, -0.5
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bias std
bias
bias - std
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bias std
bias
bias - std
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RadOn Retrieval

• 14th April 2003 Palaiseau
• Deep ice cloud
• 15th April 2003 Palaiseau
• Cirrus case

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Retrieval 14th April 2003
N0
IWC
r(D)0.022D-0.6 A(D)p/4D2
re
a
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r(D)0.0005D-1.3 A(D)0.05D1.4
N0
IWC
Retrieval 15th April 2003
re
a
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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

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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.

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1
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With running window
Vt-Z
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IWC-Z-T RJH
IWC-Z Protat et al.
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