Depolarization�ratio profiling at several wavelengths in pure Saharan dust during SAMUM 2006

Abstract

Vertical profiles of the linear particle depolarization ratio �´p 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 â�� including a new, advanced method - and a detailed error analysis. Over the whole SAMUM periode pure dust layers show a mean �´p at 532 nm of 0.31 in the range between 0.27 and 0.35 with a mean ��ngstr�¸m exponent AE (440-870 nm) of 0.18 (range 0.04 â�� 0.34), and still high mean �´p between 0.21 and 0.25 during periods with aerosol optical thickness â�¤0.1 with a mean AE of 0.76 (range 0.65 â�� 1.00), which represents a negative correlation of �´p with AE. A slight decrease of �´p with wavelength was found between 532 nm and 1064 nm from �´p = 0.31 �±0.03 to 0.27 �±0.04, respectively.