Evolution of the ice phase in tropical altocumulus: SAMUM lidar observations over Cape Verde

摘要: [1] The formation of the ice phase in tropical altocumulus has been studied with multiwavelength aerosol-cloud Raman lidar, wind Doppler and radiosonde, providing information on geometrical optical properties, cloud phase, top temperature, updraft downdraft velocity, fall speed crystals. The observations were conducted at Praia (15°N, 23.5°W), Cape Verde, North Atlantic framework Saharan Mineral Dust Experiment (SAMUM) project January February 2008. More than 200 different layers analyzed. coldest liquid had a temperature −36°C appeared height 9800 m. Tropical is found to be geometrically (262 ± 137 m) optically thin (0.69 0.61), mostly short-lived, horizontally small extents less 50 km 80% cases. A clear relationship between occurrence observed, even more after removal effects seeding, which an important process production lower multilayer systems. Because almost all (99%) showed (region nucleation begins), we conclude that deposition condensation are unimportant processes during initial glaciation. pronounced impact aerosols such as mineral particles known favorable nuclei not this region strong dust-smoke outbreaks from Africa. phases complete life cycle monitored over 5 hours. observed droplet discussed based height-resolved depolarization-ratio (cloud phase) vertical-velocity time series.