Snow Processes for Cold Regions Prediction: Snow Processes for Cold Regions Prediction: Description and Scaling Description and Scaling John Pomeroy John Pomeroy Canada Research Chair in Water Resources & Climate Change, Canada Research Chair in Water Resources & Climate Change, Centre for Hydrology, Univ Saskatchewan, Saskatoon Centre for Hydrology, Univ Saskatchewan, Saskatoon and collaborators and collaborators Tim Link (Univ Idaho), Danny Marks (USDA ARS), Tim Link (Univ Idaho), Danny Marks (USDA ARS), and Centre for Hydrology Researchers and Centre for Hydrology Researchers Tom Brown, Chris de Beer, Pablo Tom Brown, Chris de Beer, Pablo Dornes Dornes , Chad Ellis, Warren Helgason, , Chad Ellis, Warren Helgason, Nicholas Nicholas Kinar Kinar , , Gro Gro Lilbaek Lilbaek , Michael , Michael Solohub Solohub
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Snow Processes for Cold Regions Prediction: Snow Processes for Cold Regions Prediction: Description and ScalingDescription and Scaling
John Pomeroy John Pomeroy Canada Research Chair in Water Resources & Climate Change, Canada Research Chair in Water Resources & Climate Change,
Centre for Hydrology, Univ Saskatchewan, SaskatoonCentre for Hydrology, Univ Saskatchewan, Saskatoonand collaboratorsand collaborators
Tim Link (Univ Idaho), Danny Marks (USDA ARS),Tim Link (Univ Idaho), Danny Marks (USDA ARS),and Centre for Hydrology Researchersand Centre for Hydrology Researchers
Tom Brown, Chris de Beer, Pablo Tom Brown, Chris de Beer, Pablo DornesDornes, Chad Ellis, Warren Helgason, , Chad Ellis, Warren Helgason, Nicholas Nicholas KinarKinar, , GroGro LilbaekLilbaek, Michael , Michael SolohubSolohub
Snow AccumulationSnow Accumulation• Blowing Snow
Redistribution –parameterise inter-basin, inter-tile, intra-tile redistribution
• Intercepted Snow Redistribution – improve description of unloading, wind redistribution
• Snow Sublimation –parameterise and evaluate model representation from blowing, intercepted, & surface snow.
SnowmeltSnowmelt• Improved Methods to
Estimate Short and Longwave Exchange
• Terrain Effects on Turbulent Transfer
• Forest Canopies –radiation effects
• Combined Forest Canopy and Slope Effect on Energy Balance
Snow Snow -- Atmosphere ExchangeAtmosphere Exchange
SNOWPACK dU/dt
K↓ L↓K↑ L↑
QHQE
QG
Precipitation
Melt
QA
TsTi
• Longwave exchange at surface
• Shortwave penetration
• Windpumpingthrough porous structure
• Polythermal• Multiphase• Macropores
Incoming Longwave in MountainsIncoming Longwave in Mountains
0.5 0.6 0.7 0.8 0.9 1Vf
0
5
10
15
20
25
30
Ts (°
C)
Percent increase in longwave irradiance due to terrain emission due to sky view factor (Vf) and surface temperature (Ts).
Air temperature is 0°C and the clear sky emissivity is 0.65
Psychrometric Outgoing Longwave Psychrometric Outgoing Longwave Formulation for SnowFormulation for Snow
-40-35
-30-25
-20-15
-10-5
05
1017-Feb 22-Feb 27-Feb 03-Mar 08-Mar 13-Mar 18-Mar
SST
C
irtcmodel
( ) ( )[ ]apa
asaaaas rLcT
rPTQQLTLWTT/)(
/,3
sat4
ρεσρσε
Δ++−+−↓
+=
⎟⎠⎞
⎜⎝⎛Ψ−⎟⎟
⎠
⎞⎜⎜⎝
⎛=
Lz
zz
uu
mm0
ln1* κ
Roughness & Stability over Roughness & Stability over Mountain SnowMountain Snow
Expected
-40
-30
-20
-10
0
10
20
30
40
50
60
61 61.5 62 62.5 63
Day of Year
Flux
(W/m
^2)
Measured QH
Measured QE
Bulk transfer QH
(z0m = 0.001m)
Bulk transfer QE
(z0m = 0.001m)
Problems with Bulk Transfer over Problems with Bulk Transfer over Mountain SnowMountain Snow
azimuth angle
elev
atio
n an
gle
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
8570
5540
2510
50 100 200 250 300 350150
South Face Forest
azimuth angle
elev
atio
n an
gle x
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
8570
5540
2510
50 100 200 250 300 350150
North Face Forest
Slope Forest Slope Forest TransmissivityTransmissivity
τ a function of LAI,Foliage inclinationCrown coverageSlope,Aspect, Solar azimuth, Solar elevation
Radiation to Snowmelt Radiation to Snowmelt on 25on 25oo Forest Slopes, Forest Slopes,
Marmot Creek Research Marmot Creek Research Basin, AlbertaBasin, Alberta
Net Shortwave Radiation
Net Longwave Radiation
Net Allwave Radiation
Cold Region Hydrological Model Cold Region Hydrological Model CRHM CRHM
Modelling ApproachModelling Approach
Aggregated vs. Distributed
Granger Creek DischargeGranger Creek Discharge2002
Time [days]
5/01/02 5/09/02 5/17/02 5/25/02 6/02/02 6/10/02
Q [m
3 /s]
0.0
0.2
0.4
0.6
0.8
1.0ObsAggregatedDistributed
2003
Time [days]
4/17/03 4/26/03 5/05/03 5/14/03 5/23/03 6/01/03 Q
[m3 /
s]0.0
0.1
0.2
0.3
0.4
0.5ObsAggregatedDistributed
Next StepsNext Steps• Snow Unloading Study• Blowing snow parameterisation for CLASS• 3-D Blowing Snow – unsteady flow• Multi-layer snow – atmosphere model• Snow-atmosphere exchange parameterisation• Complex Terrain Forest Melt Model• Sub-grid distributions of accumulation, energy,
melt for complex terrain• CRHM basin modelling and interface to MESH
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