The role of snow in alpine hydrology
Matthias Bernhardt
Importance of the Alpine water cycle (once again) Speicher
Abflussstütze
Speicher
Snow is altering the flow regimes of river networks.
08.11.2015
Matthias Bernhardt/Karsten Schulz
2
Snow and Hydro Power
The snow storage influences the energy production in summer and winter.
Koch et al. 2011; Energies
08.11.2015
Matthias Bernhardt/Karsten Schulz
3
Snow and Floods
• Rain on snow (RoS) events can initiate significant flood events.
• The additional melt leads to an fast and significant increase of local runoff. • Especially important with respect to flash floods.
Gravelmann et al. 2015; HP
08.11.2015
Matthias Bernhardt/Karsten Schulz
4
Snow and Tourism
• A shrinking snow cover leads to the need of man made snow in skiing resorts.
• The additional need of water in head water catchments may lead to conflicts between the different consumers. Hanzer et al. 2014; Cold Regions Science and Technology
08.11.2015
Matthias Bernhardt/Karsten Schulz
5
Precipitation / runoff decoupling
Correlation between precipitation and discharge at
different time scales: (a) annual, (b) January–June and (c)
April–June.
 Spring discharge can be poorly explained by spring
precipitation (Central Spanish Pyrenees: Lopez‐Moreno
and Garcia‐Ruiz (2004)).
08.11.2015
Matthias Bernhardt/Karsten Schulz
6
Precipitation / runoff decoupling
Runoff is heavily influenced by
snow accumulation and ablation at
Zugspitze (Germany).
08.11.2015
Matthias Bernhardt/Karsten Schulz
7
Process description vs. accuracy ‐
• The model accuracy may
increase, if additional processes
are inserted in a meaningful
way.
• This effect should be tested at
different locations.
• The introduction of new
processes may lead to higher
uncertainties and to the need of
additional data and/or more
accurate data.
+
08.11.2015
complexity
Matthias Bernhardt/Karsten Schulz
Warscher et al. 2013; WRR
8
What is the reason for the observed improvements? Where are the limits?
It seems to be like this!
But, if it is really steep it is usually like this!
08.11.2015
Habilitationsvortrag von Dr. Matthias Bernhardt
9
Snow holding capacity [SWE]
Lateral snow transport
10.00
9.00
8.00
7.00
6.00
5.00
4.00
3.00
2.00
1.00
0.00
y = 45538x-2.982
0
20
40
60
80
slope [°]
SnowSlide: A simple routine for calculating gravitational snow transport; Geophysical Research Letters. Bernhardt M. and Schulz K. (2010) 08.11.2015
Matthias Bernhardt/Karsten Schulz
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Lateral snow transport
Bernhardt et al. 2009; HP
08.11.2015
Matthias Bernhardt/Karsten Schulz
11
Synchronizing processes
Uncoupled
Strasser et al. 2008. The Cryosphere
08.11.2015
Coupled
Bernhardt et al. 2012. JoH
Matthias Bernhardt/Karsten Schulz
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The observation scale
Bernhardt et al. 2012. JoH
08.11.2015
Matthias Bernhardt/Karsten Schulz
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The observation scale
Bernhardt et al. 2012. JoH
08.11.2015
Matthias Bernhardt/Karsten Schulz
14
The need for input data
CRHM, Pomeroy et al. 2007
Isnobal (Marks et al. 1999)
08.11.2015
Matthias Bernhardt/Karsten Schulz
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Modelling accuracy
Cold Regions Hydrological Model (CRHM)
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HRU‐Concept
High Performance
Very good performance on the stations.
Model run (obs): 2000‐2010 (DWD Data)
08.11.2015
Matthias Bernhardt/Karsten Schulz
16
On the need of input data inter‐comparison
Trends in der Entwicklung des Schneespeichers an der Zugspitze (1950‐2010)
08.11.2015
Matthias Bernhardt/Karsten Schulz
Höhe
1950‐
2010
Sum projected to
100Y
1600‐1900
‐0.7mm/y
‐70mm
1900‐2200
‐2.9mm/y
‐290mm
2200‐2500
‐3.8mm/y
‐380mm
2500‐3000
‐5.6mm/y
‐560mm
17
On the need of process inter‐comparison.
Snobal / Input Zugspitze Summit 1.8.2005‐31.12.2006: Kg/m² (Albedo decay)
Kg/m² (Albedo Baker)
Kg/m² (Albedo Winstral)
(z.B. Marks et al. 2008: Comparing Simulated and Measured Sensible and Latent Heat Fluxes over Snow under a Pine Canopy to Improve an Energy Balance Snowmelt Model / Journal of Hydrometeorology) Kg/m² (Albedo Essery)
Kg/m² (Albedo Essery)
Kg/m² (Albedo Essery)
Essery and Etchevers (2004): Parameter sensitivity in simulations of snowmelt. JOURNAL OF GEOPHYSICAL RESEARCH
Baker, Rutschy and Wall (1990): The Albedo Decay of Prairie Snows. JOURNAL OF APPLIED METEOROLOGY
08.11.2015
Habilitationsvortrag von Dr. Matthias Bernhardt
18
PUB
What strategy is favourable in ungauged catchments?
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Data interpolation
Usage of data of a comparable site?
Atmospheric re‐analysis models?
?
08.11.2015
Matthias Bernhardt/Karsten Schulz
19
ERA‐Interim as an example
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Global availability
3hrs resolution
Spatial resolution: 80km
60 vertical pressure levels
Easily accessible
08.11.2015
Matthias Bernhardt/Karsten Schulz
20
ERA‐Interim as an example
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The SWE development is only covered to some extent by ERA‐Interim
The reason can be manly traced back to biased temperature values
Errors in precipitation are masked to some extent during the winter season
Is this true all over the world. What can be improved by using the existent assimilation
schemes.
08.11.2015
Matthias Bernhardt/Karsten Schulz
21
Snow from remote sensing and photography.
PRACTISE – Photo Rectification And ClassificaTIon SoftwarE (V.1.0+2.0) Härer et al. 2013 (GMD)
08.11.2015
Habilitationsvortrag von Dr. Matthias Bernhardt
22
NDSI threshold calibration
PRACTISE – Photo Rectification And ClassificaTIon SoftwarE (V.2.0) Härer et al. 2015 (GMD)
08.11.2015
Matthias Bernhardt/Karsten Schulz
23
Landsat (19/06/2013)
NDSI = 0.3
NDSI = 0.4
08.11.2015
Matthias Bernhardt/Karsten Schulz
24
Snow from LIDAR measurements
08.11.2015
25
Snow from LIDAR measurements
Validation LIDAR: LWD station (19/06/2013)
Snow height:
181.6cm (LIDAR)
178.6cm (LWD‐Station )
08.11.2015
26
Snow from LIDAR measurements
Height difference (19/06/2013 ‐ 01/08/2013)
in m
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27
Learning from data
Principle component 1 (77%)
Component loading
• Elevation gradient
• Slides
08.11.2015
Matthias Bernhardt/Karsten Schulz
28
Learning from data
Principle component2 (16%)
Component loading
• Artifical snow transport
• Noice
08.11.2015
Matthias Bernhardt/Karsten Schulz
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Learning from data
Principle component 3 (7%)
• Radiation
Component loading
Meters
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Thank you!