Editorial Type:
Article
Article Type:
Research Article

Cloud Liquid Water and Ice Content Retrieval by Multiwavelength Radar

Nicolas Gaussiat Université Paul Sabatier, Observatoire Midi-Pyrénées, Laboratoire d'Aérologie, Toulouse, France

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Henri Sauvageot Université Paul Sabatier, Observatoire Midi-Pyrénées, Laboratoire d'Aérologie, Toulouse, France

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Anthony J. Illingworth Department of Meteorology, University of Reading, Reading, United Kingdom

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Print Publication:
01 Sep 2003
DOI:
https://doi.org/10.1175/1520-0426(2003)020<1264:CLWAIC>2.0.CO;2
Page(s):
1264–1275
Restricted access

Abstract

Cloud liquid water and ice content retrieval in precipitating clouds by the differential attenuation method using a dual-wavelength radar, as a function of the wavelength pair, is first discussed. In the presence of non-Rayleigh scatterers, drizzle, or large ice crystals, an ambiguity appears between attenuation and non-Rayleigh scattering. The liquid water estimate is thus biased regardless of which pair is used. A new method using three wavelengths (long λl, medium λm, and short λs) is then proposed in order to overcome this ambiguity. Two dual-wavelength pairs, (λl, λm) and (λl, λs), are considered. With the (λl, λm) pair, ignoring the attenuation, a first estimate of the scattering term is computed. This scattering term is used with the (λl, λs) pair to obtain an estimate of the attenuation term. With the attenuation term and the (λl, λm) pair, a new estimate of the scattering term is computed, and so on until obtaining a stable result. The behavior of this method is analyzed through a numerical simulation and the processing of field data from 3-, 35-, and 94-GHz radars.

Corresponding author address: Dr. Henri Sauvageot, Université Paul Sabatier (Toulouse III), Centre de Recherches Atmosphériques, Campistrous, 65300 Lannemezan, France. Email: sauh@aero.obs-mip.fr

Abstract

Cloud liquid water and ice content retrieval in precipitating clouds by the differential attenuation method using a dual-wavelength radar, as a function of the wavelength pair, is first discussed. In the presence of non-Rayleigh scatterers, drizzle, or large ice crystals, an ambiguity appears between attenuation and non-Rayleigh scattering. The liquid water estimate is thus biased regardless of which pair is used. A new method using three wavelengths (long λl, medium λm, and short λs) is then proposed in order to overcome this ambiguity. Two dual-wavelength pairs, (λl, λm) and (λl, λs), are considered. With the (λl, λm) pair, ignoring the attenuation, a first estimate of the scattering term is computed. This scattering term is used with the (λl, λs) pair to obtain an estimate of the attenuation term. With the attenuation term and the (λl, λm) pair, a new estimate of the scattering term is computed, and so on until obtaining a stable result. The behavior of this method is analyzed through a numerical simulation and the processing of field data from 3-, 35-, and 94-GHz radars.

Corresponding author address: Dr. Henri Sauvageot, Université Paul Sabatier (Toulouse III), Centre de Recherches Atmosphériques, Campistrous, 65300 Lannemezan, France. Email: sauh@aero.obs-mip.fr

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Journal of Atmospheric and Oceanic Technology

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