Vertical structure of particle properties and water content in noctilucent clouds

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Abstract

[1] Noctilucent clouds (NLC) have been observed by lidar in Norway (69N, 16E) between 1998 and 2005 to study the vertical variation of particle properties inside the clouds. We find that the maximum size of the particles is reached below the altitude of maximum backscattering. The mean radius of the particle ensemble increases from 38.1 ± 1.1 nm 0.9 km above the peak to 58.5 ± 2.5 nm, 0.6 km below the peak of the layer. At the peak the particle size is 47.7 nm. The distribution width increases from 14.0 nm to 17.7 nm and the number density decreases from 133/cm3 to 29/cm3 from top to bottom of the layer. The unexpected observation that the largest particles are not found at the peak of the layer indicates that the supersaturated region extends below the brightness peak of the layer. We observe that the distribution width is an indicator for the cloud age.

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