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research article

Orographic effects on snow deposition patterns in mountainous terrain

Mott, R.
•
Scipion, D.  
•
Schneebeli, M.  
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2014
Journal of Geophysical Research: Atmospheres

Orographic lifting of air masses and other topographically modified flows induce cloud and precipitation formation at larger scales and preferential deposition of precipitation at smaller scales. In this study, we examine orographic effects on small-scale snowfall patterns in Alpine terrain. A polarimetric X-band radar was deployed in the area of Davos (Switzerland) to determine the spatial variability of precipitation. In order to relate measured precipitation fields to flow dynamics, we model flow fields with the atmospheric prediction model Advanced Regional Prediction System. Additionally, we compare radar reflectivity fields with snow accumulation at the surface as modeled by Alpine3D. We investigate the small-scale precipitation dynamics for one heavy snowfall event in March 2011 at a high resolution of 75 m. The analysis of the vertical and horizontal distribution of radar reflectivity at horizontal polarization and differential reflectivity shows polarimetric signatures of orographic snowfall enhancement near the summit region. Increasing radar reflectivity at horizontal polarization over the windward slopes toward the crest and downwind decreasing reflectivity over the leeward slopes is observed. The temporal variation of the location of maximum concentration of snow particles is partly attributed to the effect of preferential deposition of snowfall: For situations with strong horizontal winds, the concentration maximum is shifted from the ridge crest toward the leeward slopes. Qualitatively, we discuss the relative role of cloud microphysics such as the seeder-feeder mechanism versus atmospheric particle transport in generating the observed snow deposition at the ground. Key Points Orographic snowfall enhancement near the summit region Preferred snow deposition on leeward slopes Snow drift affects reflectivity patterns observed by radar

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Type
research article
DOI
10.1002/2013Jd019880
Web of Science ID

WOS:000332994600021

Author(s)
Mott, R.
Scipion, D.  
Schneebeli, M.  
Dawes, N.
Berne, A.  
Lehning, M.  
Date Issued

2014

Publisher

Wiley-Blackwell

Published in
Journal of Geophysical Research: Atmospheres
Volume

119

Issue

3

Start page

1419

End page

1439

Subjects

snowfall

•

dual-polarized radar

•

seeder-feeder mechanism

•

orographic precipitation

•

flow field

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
CRYOS  
LTE  
Available on Infoscience
May 19, 2014
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/103488
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