matt macdonald school of geosciences, university of ... - ec workshop... · matt macdonald . school...

Matt MacDonald School of GeoSciences, University of Edinburgh m.k.macdonald@sms.ed.ac.uk 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