Classification of Arctic multilayer clouds using radiosonde and radar data in Svalbard
<p>Multilayer clouds (MLCs) occur more often in the Arctic than globally. In this study we present the results of a detection algorithm applied to radiosonde and radar data from an 1-year time period in Ny-Ålesund, Svalbard. Multilayer cloud occurrence is found on 29 % of the invest...
| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2019-04-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/19/5111/2019/acp-19-5111-2019.pdf |
| Summary: | <p>Multilayer clouds (MLCs) occur more often in the Arctic than globally. In this
study we present the results of a detection algorithm applied to radiosonde
and radar data from an 1-year time period in Ny-Ålesund, Svalbard.
Multilayer cloud occurrence is found on 29 % of the investigated days. These
multilayer cloud cases are further analysed regarding the possibility of ice
crystal seeding, meaning that an ice crystal can survive sublimation in a
subsaturated layer between two cloud layers when falling through this layer.
For this we analyse 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 <span class="inline-formula"><i>r</i>=400</span> <span class="inline-formula">µ</span>m 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
(100 % includes all days, as well as non-cloudy 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).
There are various deviations between the relative humidity profiles and the
radar images, e.g. due to the lack of ice-nucleating particles (INPs) and
cloud condensation nuclei (CCN). Additionally, horizontal wind drift of the
radiosonde and time restriction when comparing radiosonde and radar data
cause further deviations. In order to account for some of these deviations,
an evaluation by manual visual inspection is done for the non-seeding cases.</p> |
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| ISSN: | 1680-7316 1680-7324 |