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

1. 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: Thomas.Boerner@dlr.de (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 0.4 20° a 50° 10 dbZZyy 22 dbZ c3 0.4  H 1 10° a 20° 10 dbZZyy 22 dbZ c4 0  H 0.45 0°  a 20° 22 dbZZyy 35 dbZ c5 0  H 0.45 20°  a 50° 22 dbZZyy 35 dbZ c6 0.45  H 1 0°  a 20° 22 dbZZyy 35 dbZ c7 0.45  H 1 20°  a 50° 22 dbZZyy 35 dbZ c8 0.6  H 1 15°  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