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  4. Spatial variability in snow precipitation and accumulation in COSMO–WRF simulations and radar estimations over complex terrain
 
research article

Spatial variability in snow precipitation and accumulation in COSMO–WRF simulations and radar estimations over complex terrain

Gerber, Franziska  
•
Besic, Nikola  
•
Sharma, Varun  
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October 4, 2018
The Cryosphere

Snow distribution in complex alpine terrain and its evolution in the future climate is important in a variety of applications including hydropower, avalanche forecasting and freshwater resources. However, it is still challenging to quantitatively forecast precipitation, especially over complex terrain where the interaction between local wind and precipitation fields strongly affects snow distribution at the mountain ridge scale. Therefore, it is essential to retrieve high-resolution information about precipitation processes over complex terrain. Here, we present very-high-resolution Weather Research and Forecasting model (WRF) simulations (COSMO-WRF), which are initialized by 2.2 km resolution Consortium for Small-scale Modeling (COSMO) analysis. To assess the ability of COSMO-WRF to represent spatial snow precipitation patterns, they are validated against operational weather radar measurements. Estimated COSMO-WRF precipitation is generally higher than estimated radar precipitation, most likely due to an overestimation of oro-graphic precipitation enhancement in the model. The high precipitation amounts also lead to a higher spatial variability in the model compared to radar estimates. Overall, an autocorrelation and scale analysis of radar and COSMO-WRF precipitation patterns at a horizontal grid spacing of 450 m show that COSMO-WRF captures the spatial variability normalized by the domain-wide variability in precipitation patterns down to the scale of a few kilometers. However, simulated precipitation patterns systematically show a lower variability on the smallest scales of a few hundred meters compared to radar estimates. A comparison of spatial variability for different model resolutions gives evidence for an improved representation of local precipitation processes at a horizontal resolution of 50 m compared to 450 m. Additionally, differences of precipitation between 2830 m above sea level and the ground indicate that near-surface processes are active in the model.

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Type
research article
DOI
10.5194/tc-12-3137-2018
Author(s)
Gerber, Franziska  
Besic, Nikola  
Sharma, Varun  
Mott, Rebecca
Daniels, Megan
Gabella, Marco
Berne, Alexis  
Germann, Urs
Lehning, Michael  
Date Issued

2018-10-04

Published in
The Cryosphere
Volume

12

Issue

10

Start page

3137

End page

3160

Subjects

LARGE-EDDY SIMULATIONS

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NUMERICAL WEATHER PREDICTION

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IMMERSED-BOUNDARY METHOD

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SEEDER-FEEDER MECHANISM

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OROGRAPHIC PRECIPITATION

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FORECASTING-MODEL

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SENSITIVITY

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MESOSCALE

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DEPTH

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ENHANCEMENT

Editorial or Peer reviewed

REVIEWED

Written at

EPFL

EPFL units
LTE  
CRYOS  
Available on Infoscience
October 18, 2018
Use this identifier to reference this record
https://infoscience.epfl.ch/handle/20.500.14299/149126
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