Depolarization ratio profiling at several wavelengths in pure Saharan dust during SAMUM 2006 |
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Authors: | By VOLKER FREUDENTHALER MICHAEL ESSELBORN MATTHIAS WIEGNER BIRGIT HEESE MATTHIAS TESCHE ALBERT ANSMANN DETLEF MÜLLER DIETRICH ALTHAUSEN MARTIN WIRTH REAS FIX GERHARD EHRET PETER KNIPPERTZ CARLOS TOLEDANO JOSEF GASTEIGER MARKUS GARHAMMER MEINHARD SEEFELDNER |
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Institution: | Meteorological Institute, Ludwig-Maximilians-Universität, Theresienstr. 37, 80333 Munich, Germany;;Institute of Atmospheric Physics, German Aerospace Center (DLR), Oberpfaffenhofen, 82234 Wessling, Germany;;Leibniz Institute for Tropospheric Research, Permoserstr. 15, 04318 Leipzig, Germany;;Institute for Atmospheric Physics, Johannes Gutenberg University, Becherweg 21, 55099 Mainz, Germany |
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Abstract: | Vertical profiles of the linear particle depolarization ratio of pure dust clouds were measured during the Saharan Mineral Dust Experiment (SAMUM) at Ouarzazate, Morocco (30.9°N, –6.9°E), close to source regions in May–June 2006, with four lidar systems at four wavelengths (355, 532, 710 and 1064 nm). The intercomparison of the lidar systems is accompanied by a discussion of the different calibration methods, including a new, advanced method, and a detailed error analysis. Over the whole SAMUM periode pure dust layers show a mean linear particle depolarization ratio at 532 nm of 0.31, in the range between 0.27 and 0.35, with a mean Ångström exponent (AE, 440–870 nm) of 0.18 (range 0.04–0.34) and still high mean linear particle depolarization ratio between 0.21 and 0.25 during periods with aerosol optical thickness less than 0.1, with a mean AE of 0.76 (range 0.65–1.00), which represents a negative correlation of the linear particle depolarization ratio with the AE. A slight decrease of the linear particle depolarization ratio with wavelength was found between 532 and 1064 nm from 0.31 ± 0.03 to 0.27 ± 0.04. |
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