J. Helmert, G. Zängl, M. Raschendorfer, D. Mironov, H. Frank, B. Ritter
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Transcript of J. Helmert, G. Zängl, M. Raschendorfer, D. Mironov, H. Frank, B. Ritter
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J. Helmert, G. Zängl, M. Raschendorfer, D. Mironov, H. Frank, B. Ritter
Enhancement of the single layer snow model in TERRA: Global
numerical experiments
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Outline
Computing the snow density
Snow depth, snow heat conductivity
Scalar roughness length over snow
Global numerical experiments
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Single layer snow model
sT
snowT
sTsh
1soT
snowf )1( snowf
radQ
SWEs ,
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Snow depth, heat conductivity, snow density:
ft
SWEh
nw
s
s)(
sn
sfsnn
sns PSWE
PTSWEt
)()( ,1
sfs P,,
nns SWE,
88.1
22.2
w
ns
s
Routine
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Snow density: Experiment
fs
sns
n
ns
n
fs
sns
n
wfns
PSWESWE
PSWEhh
,1
1
,
)(
fs
sns
ns
nns PSWE
PSWE
,
1
fsfs hP ,,,
ns
nns hSWE ,,
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Case study: Snow storm „Daisy“January 2010
Pictures from Tagesschau.de
PEPS 2010010812
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Experiment: Daisy 2010010800 96h GME
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Experiment: Daisy 2010010800 96h GME
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Experiment: Daisy 2010010800 96h GME
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Fresh snow
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Snow depth
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Snow density
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ROUTI - EXP
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ROUTI - EXP
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The main camp for the SHEBA project was based around the CCG Ice Breaker DeGroseilliers
Baltimore site with ridge in background.
Surface Heat Budget of the Arctic Ocean (SHEBA) field experiment
http://www.esrl.noaa.gov/psd/psd3/arctic/sheba/
http://www.crrel.usace.army.mil/sid/SeaIceDynamics/SHEBA.htm
Scalar roughness length over snow
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Scalar roughness length over snow
Experiment: additional variable for z0t: gz0s:
Minimum: zT= 1.E-4 m
Andreas et al., 2004 Ice station Weddel
GME Exp
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Tzszst
szs
zfzfz
gzSWESWE
SWEf
0,00,0
0min0,
)1(
Example:
SWE=40mm, SWEmin=10mmbeta_s=0.408s^2/mz0=10cm
f_s=0.09z0t=9.1cm
Scalar roughness length over snow: SURFEX
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Experiment 7667
Computing the adapted snow density with implications for snow depth, snow heat conductivity
Scalar roughness length over snow
Winter 2009/2010; first month: December 2009
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Verification T850 BIAS
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Verification G500 ANOC
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Verification
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Europe
East Sibiria
North America
EXP 7667 SNOW 02.12.2009-31.12.2009 00 UTC i192f
Global Verification
SK: -0.57SK: 2.37 SK: -0.39
SK: -4.21 SK: -1.88 SK: -0.27
SK: 1.32 SK: 0.22 SK: 0.69
T_2M TDD_2M P_SURF
North-West SibiriaSK: -4.03
SK: 0.45 SK: -3.82
South-West SibiriaSK: -4.74
SK: -0.14 SK: -2.74
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Routine snow density formulation leads to underestimation of snow depth, overestimation of snow heat conductivity
Revised formulation could alleviate to a certain degree this problem
Introduction of scalar roughness length over snow accounts for decrease in roughness length with increasing grid point snow amount
Verification of EXP7667 for December 2009 shows positive impact of model changes for regions with warm 2m-temperature bias
Conclusions