1. Dual wavelength lidar observation of tropical high-altitude cirrus clouds during the ALBATROSS 1996 Campaign
- Author
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Georg Beyerle, I. S. McDermid, Roland Neuber, Otto Schrems, and H.-J. Schäfer
- Subjects
010504 meteorology & atmospheric sciences ,Backscatter ,Atmospheric sciences ,01 natural sciences ,Aerosol ,010309 optics ,Wavelength ,Geophysics ,Altitude ,Lidar ,13. Climate action ,0103 physical sciences ,General Earth and Planetary Sciences ,Environmental science ,Cirrus ,Tropopause ,Optical depth ,0105 earth and related environmental sciences - Abstract
Dual wavelength aerosol lidar observations of tropical high-altitude cirrus clouds were performed during the ALBATROSS 1996 campaign aboard the research vessel “POLARSTERN” on the Atlantic ocean in October–November 1996. On the basis of 57 hours of night-time observations between 23.5°N and 23.5°S we find in 72% of the altitude profiles indications of the presence of cirrus cloud layers. This percentage drops to 32% at subtropical latitudes (23.5°–30°) based on 15 hours of data. About one-half of the subtropical and tropical cirrus layers are subvisual with an optical depth of less than 0.03 at a wavelength of 532 nm. In general the clouds exhibit high spatial and temporal variability on scales of a few tens of meters vertically and a few hundred meters horizontally. No clouds are observed above the tropopause. An abrupt change in the relation between the color ratios of the parallel and perpendicular backscatter coefficients at about 240 K is interpreted in terms of changes of particle shape and/or size distribution. At temperatures between 195 and 255 K only a small fraction of the observations are consistent with the presence of small particles with dimensions of less than 0.1 µm. more...
- Published
- 1998
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