Thomas b rner 1 martin hagen 2 david bebbington 3
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a = 0 . a = 45 . a = 90 . A first approach to unsupervised Entropy-Alpha-classification of full-polarimetric weather-radar data. Thomas Börner (1) , Martin Hagen (2) , David Bebbington (3) Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR)

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Thomas Börner (1) , Martin Hagen (2) , David Bebbington (3)

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Thomas b rner 1 martin hagen 2 david bebbington 3

a = 0

a = 45

a = 90

A first approach to unsupervised Entropy-Alpha-classification of full-polarimetric weather-radar data

Thomas Börner(1), Martin Hagen(2), David Bebbington(3)

Deutsches Zentrum für Luft- und Raumfahrt e.V. (DLR)

(1)Institut für Hochfrequenztechnik und Radarsysteme, (2)Institut für Physik der Atmosphäre

P.O.-Box 1116, D-82230 Weßling, Germany, Phone/Fax: +49-8153-28-2368 / -1449, Email: [email protected]

(3)University of Essex, Electronic Systems Engineering Department, UK

  • Abstract: In this contribution we will show a first approach of unsupervised classification of weather-radar data using the polarimetric Entropy-Alpha target decomposition (Cloude, Pottier, 1997). The classification algorithm consists of the following steps:

    Prepare the polarimetric time series data (DLR’s POLDIRAD): correct phase changes due to propagation and Doppler effects on a pulse to pulse basis.

    Calculate the Covariance (or Coherence) matrix from the [S] matrix. Ensemble averaging preserves statistical fluctuations of targets over time.

    Diagonalisation of the hermitian Covariance matrix yields dominant physical scattering mechanisms, represented and interpreted by Entropy H and Alpha-angle a.

    Choose areas in the H-a plane for classification. Refinement is done by adding copolar reflectivity Z to the classification scheme.

Entropy Alpha Target Decomposition

Simplified interpretation of a: ellipticity of scattering objects.

Physical scattering mechanisms

Degree of disorder in the scattering process.

Contribution of each scattering mechanism

RHI

classification

result

PPI

classification

result

Classification Scheme

c1 0  H 0.4 0° a 20°10 dbZZyy 22 dbZ

c2 0  H 0.420° a 50°10 dbZZyy 22 dbZ

c3 0.4  H 110° a 20°10 dbZZyy 22 dbZ

c4 0  H 0.45 0°  a 20°22 dbZZyy 35 dbZ

c5 0  H 0.4520°  a 50°22 dbZZyy 35 dbZ

c60.45  H 1 0°  a 20°22 dbZZyy 35 dbZ

c70.45  H 120°  a 50°22 dbZZyy 35 dbZ

c8 0.6  H 115°  a 50°35 dbZZyy 64 dbZ

c9 0  H 1 0°  a 50° 0 dbZZyy < 10 dbZ

H-a plane

H-a plane

Z-H plane

Z-H plane

Z-a plane

Z-a plane


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