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Classification of Arctic multilayer clouds using radiosonde and radar data

Preprint published in 2018 by Maiken Vassel, Luisa Ickes, Marion Maturilli, Corinna Hoose
This paper is available in a repository.
This paper is available in a repository.

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Preprint: policy unknown
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Postprint: policy unknown
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Multilayer clouds (MLC) occur more often in the Arctic than globally. In this study a ground-based detection algorithm is developed using radiosoundings and radar from an one-year time period in Ny-Ålesund, Svalbard. The detection algorithm results in a multilayer cloud occurrence of 29 % of the investigated days. These multilayer cloud cases are further analysed regarding the possibility of ice crystal seeding. Ice crystal seeding means that an ice crystal can survive sublimation in a subsaturated layer between two cloud layers when falling through this layer. For this we analyse height profiles of relative humidity with respect to ice to identify super- and subsaturated air layers. Then the sublimation of an ice crystal of an assumed initial size of r = 100 μm on its way through the subsaturated layer is calculated. If the ice crystal still exists when reaching a lower supersaturated layer, ice crystal seeding can potentially take place. Seeding cases are found often, in 23 % of the investigated days. The identification of seeding cases is limited by the radar signal inside the subsaturated layer. Clearly separated multilayer clouds, defined by a clear interstice in the radar image, do not interact through seeding (9 % of the investigated days). Since there are various deviations between the relative humidity profiles and the radar images, for the non-seeding cases an evaluation by manual visual inspection is additionally done.

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