matt macdonald school of geosciences, university of ... - ec workshop... · matt macdonald . school...
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Matt MacDonald School of GeoSciences, University of Edinburgh [email protected] John Pomeroy1, Richard Essery2, Al Pietroniro3
1 Centre for Hydrology, University of Saskatchewan 2 School of Geosciences, University of Edinburgh 3 Meteorological Service of Canada, Environment Canada
1) Evaluate simulations of snow transport, sublimation, accumulation, melt and infiltration to frozen soils using CLASS in a variety of windswept cold regions
2) Examine possible model improvements from additions of blowing snow transport and sublimation algorithms.
3) Examine possible model improvements from changes to turbulent transfer, snowcover depletion, snow densification, albedo decay, thermal conductivity, meltwater and frozen soil parameterisations.
Inter-tile and inter-grid square snow redistribution
QS
QS
QT
QT
TOPOGRAPHICDEPRESSION
WINDWARD
LEEWARD
GRASS FORESTBAREGROUND
SHRUB
QS
QT
WINDWARD,BARE GROUND,
GRASS
LEEWARD,FOREST
SHRUB,DEPRESSIONBLOWING SNOW
BLOWING SNOW
BLOW
ING
SNOW
IF CAPACITY/THRESHOLDIS EXCEEDED
QS
QS
QT
QT
TOPOGRAPHICDEPRESSION
WINDWARD
LEEWARD
GRASS FORESTBAREGROUND
SHRUB
QS
QT
QS
QS
QT
QT
TOPOGRAPHICDEPRESSION
WINDWARD
LEEWARD
GRASS FORESTBAREGROUND
SHRUB
QS
QT
WINDWARD,BARE GROUND,
GRASS
LEEWARD,FOREST
SHRUB,DEPRESSION
WINDWARD,BARE GROUND,
GRASS
LEEWARD,FOREST
SHRUB,DEPRESSIONBLOWING SNOW
BLOWING SNOW
BLOW
ING
SNOW
BLOWING SNOW
BLOWING SNOW
BLOW
ING
SNOW
IF CAPACITY/THRESHOLDIS EXCEEDED
Prairie Blowing Snow Model (PBSM) Pomeroy and Li (2000) numerically-integrated, fully-
developed snow transport and sublimation calculation modified for developing flow (Pomeroy et al., 2007)
Snow mass balance for a landscape unit j:
j
jnettj
s
j
lq
qPdt
dS ,+−=P: Snowfall rate (kg/s/m2) qs
j: Blowing snow sublimation (kg/s/m2) qt,net
j: Net snow transport into j (kg/s/m) lj: length of landscape unit in wind
direction (m)
Rocky Mountains
Prairies
Arctic
Boreal Forest
Sub-arctic
A network of WECC Observatories combine meteorological, hydrological, ecosystem, and cryospheric observations with multi-scale coupled models from the surface to the atmosphere.
Marmot Creek Research Basin Fisera Ridge
Wolf Creek Research Basin Granger Basin
Rocky Mountains Kananaskis Country
~2310 m ASL
Alpine tundra ridge just above treeline
200 m transect (snow surveys performed)
3 meteorological stations
15 km South of Whitehorse
1310-2100 m ASL 8 km2
Subarctic tundra cordillera
5 meteorological stations
PBSM coded into MESH inter-tile snow
redistribution
Single column tests at Fisera Ridge Windswept Winters 2007/2008 &
2008/2009 Three models PBSM + Snobal (CRHM) CLASS (calibrated) CLASS-PBSM (calibrated)
Year RMSE (cm) MB
CRHM CLASS CLASS-
PBSM
CRHM CLASS CLASS-
PBSM 2007/2008 7.2 73.9 18.4 0.07 15.2 3.42 2008/2009 8.5 33.7 19.0 0.20 1.57 0.52
Flow over ridge top and into forest
NF Ridge top
SF- top
SF- bottom Forest
Blowing snow sublimation
Tiles follow an aerodynamic sequence
MESH-PBSM
PBSM improves simulation CLASS overestimated melt
Year
MESH-PBSM RMSE MB R2
2007/2008 20.6 -0.18 0.68 2008/2009 8.9 -0.05 0.90
5 interactive tiles
MESH
MESH-PBSM
Year
MESH MESH-PBSM RMSE MB R2 RMSE MB R2
1998/1999 18.4 0.24 0.28 17.3 0.27 0.55 2000/2001 23.3 -0.23 -0.49 19.9 -0.18 0.39 2003/2004 18.4 -0.84 -0.09 15.1 -0.82 0.64
▪ Evaluation statistics do not reflect decreased snow accumulation on UB and PLT (1998/1999 and 2000/2001) ▪ No snow surveys
Granger Basin blowing snow sublimation 10-37% of snowfall (CRHM) 12-36% of snowfall (MESH-PBSM)
Instrumentation at two prairie sites in Alberta
Driving data for two winters Manual snow surveys Soil moisture
Nier
Bow Valley
Canadian Land Surface Scheme CLASS 3.6
2 options for 12
parameterisations 212 = 4,096 models
▪ Turbulent exchange ▪ Snow processes ▪ Soil processes
1. Turbulent exchange 1. Monin-Obukhov 2. Bulk Richardson
2. Z0,M/Z0,H 1. = 3.0 2. = 10.0
3. Blowing snow 1. None 2. PBSM (Pomeroy and Li, 2000)
4. Snow cover fraction 1. Linear 2. tanh
5. Fresh snow density 1. f(T, u) 2. f(T)
6. Snow compaction 1. empirical, decay 2. compactive viscosity
7. Snow albedo decay 1. Linear decay 2. Efficient spectral
8. Snow thermal conductivity 1. Yen (1981) 2. Sturm et al. (1997)
9. Snow liquid water 1. f(snow density) 2. maximum = 4%
10. Soil thermal conductivity 1. Côte & Konrad (2005) with de Vries
(1963) averaging 2. de Vries (1963)
11. Soil freezing point depression 1. None 2. Water potential-freezing point
12. Infiltration 1. Mein-Larson (1973) 2. Empirical, frozen soils (Zhao & Gray,
1999)
*Careful to validate with soil moisture measurements from a single point
*Same maximum albedo values used
Which parameterisations produce the greatest percent difference in error for SWE? Percent difference
in RMSE for SWEBow Valley Nier
Process 2011 2011-2012 2011-2012Tubulent exchange 4.4% 4.7% 47%Z0m/Z0h 0.0% 0.0% 0.1%Blowing snow 1.4% 27% 2.5%Snow cover fraction 0.5% 1.8% 0.8%Fresh snow density 1.2% 0.7% 4.2%Snow compaction 0.8% 6.2% 3.8%Snow albedo 1.8% 0.8% 4.7%Snow thermal conductivity 1.1% 1.7% 7.1%Snow liquid water 0.1% 0.5% 0.8%Infiltration 3.1% 5.7% 2.8%Soil thermal conductivity 0.2% 2.8% 13%Soil freezing point depression 0.0% 0.0% 0.0%Mean RMSE (MM) 7.8 6.6 6.2
> 10% < 1%
Turbulent exchange, blowing snow & soil thermal conductivity result in greatest difference Varies by year &
location
Which parameterisations produce the greatest percent difference in error for soil water?
> 10% < 1%
Turbulent exchange & infiltration result in greatest difference at both sites Varies by year
Bow Valley NierProcess 2011-2012 2010-2011 2011-2012Tubulent exchange 45% 18% 165%Z0m/Z0h 0.0% 6.5% 0.0%Blowing snow 5.6% 0.8% 4.0%Snow cover fraction 0.8% 0.8% 15%Fresh snow density 0.3% 0.2% 8.3%Snow compaction 3.5% 5.8% 181%Snow albedo 0.5% 0.1% 1.7%Snow thermal conductivity 0.4% 4.1% 35%Snow liquid water 0.0% 0.0% 0.1%Infiltration 32% 85% 305%Soil thermal conductivity 64% 2.9% 72%Soil freezing point depression 0.0% 0.0% 0.0%Mean PBIAS (%) 11.4 -32.8 9.8
PBSM and Frozen Soil Infiltration parameterisations improve or do not degrade CLASS simulations in windswept cold regions environments
Varied changes to turbulent transfer, albedo, snow cover depletion, snow densification and thermal conductivity algorithms did not consistently improve CLASS performance
Concern that single snow layer in CLASS limits potential for improved simulation