Comparing model and measured ice crystal concentrations in orographic clouds during the INUPIAQ campaign
This paper assesses the reasons for high ice number concentrations observed in orographic clouds by comparing in situ measurements from the Ice NUcleation Process Investigation And Quantification field campaign (INUPIAQ) at Jungfraujoch, Switzerland (3570 m a.s.l.) with the Weather Research and...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-04-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/16/4945/2016/acp-16-4945-2016.pdf |
| Summary: | This paper assesses the reasons for high ice number
concentrations observed in orographic clouds by comparing in situ
measurements from the Ice NUcleation Process Investigation And Quantification
field campaign (INUPIAQ) at Jungfraujoch, Switzerland
(3570 m a.s.l.) with the Weather Research and Forecasting model
(WRF) simulations over real terrain surrounding Jungfraujoch. During the 2014
winter field campaign, between 20 January and 28 February, the model
simulations regularly underpredicted the observed ice number concentration by
10<sup>3</sup> L<sup>−1</sup>. Previous literature has proposed several processes for
the high ice number concentrations in orographic clouds, including an
increased ice nucleating particle
(INP) concentration, secondary ice multiplication and the advection of
surface ice crystals into orographic clouds. We find that increasing INP
concentrations in the model prevents the simulation of the mixed-phase clouds
that were witnessed during the INUPIAQ campaign at Jungfraujoch.
Additionally, the inclusion of secondary ice production upwind of
Jungfraujoch into the WRF simulations cannot consistently produce enough ice
splinters to match the observed concentrations. A flux of surface hoar crystals
was included in the WRF model, which simulated ice concentrations
comparable to the measured ice number concentrations, without depleting the
liquid water content (LWC) simulated
in the model. Our simulations therefore suggest that high ice concentrations
observed in mixed-phase clouds at Jungfraujoch are caused by a flux of
surface hoar crystals into the orographic clouds. |
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| ISSN: | 1680-7316 1680-7324 |