ISSUES IN APPLICATION OF MACROSCALE HYDROLOGY MODELS TO HIGH LATITUDE DOMAINS

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ISSUES IN APPLICATION OF MACROSCALE HYDROLOGY
MODELS TO HIGH LATITUDE DOMAINS

• Dennis P. Lettenmaier, Jennifer C. Adam, and
  Laura C. Bowling
• Department of Civil and Environmental Engineering
• University of Washington
• AGU Fall Meeting
• San Francisco
• December 6, 2002

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• Challenges in
• Process understanding (frozen soils, snow
  sublimation and redistribution, role of lakes and
  wetlands)
• Observations (low network density, measurement
  issues e.g. precipitation undercatch, humidity
  at low T)
• Modeling (parameterizations appropriate to arctic
  environments scaling)

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Lakes and wetlands
Source San Diego State University Global Change
Research Group
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Lakes and Wetlands

• Attenuation of seasonal runoff
• Increase in latent heat, decrease in sensible heat

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Blowing Snow and Sublimation
Günter Eisenhardt 3.31.2002, Iceland
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PILPS-2e -- Effect of high (ECMWF) vs low
(CLASS) sublimation on mean annual predicted
discharge
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Permafrost and frozen ground

• Limits meltwater infiltration into soil
• Restricts soil moisture storage capacity which
  changes over time
• Limits importance of groundwater flow

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Observation Issues
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Precipitation Gauges of the World

• 50 types of National Standard gauges
• Sevruk et al., 1989

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Wind-Induced Undercatch

• Influencing Factors
• Wind speed
• Temperature
• Gauge type
• Gauge height
• Windshield
• Exposure

Nespor and Sevruk, 1999
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Gridded Catch Ratios
Catch Ratio ()
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Modeling Challenges
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Arctic drainage basin
Mackenzie
ungauged area
gauged area
Lena
Ob
Yenesei
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VIC Arctic Modeling
Annual average days of snow cover for the Ob
River basin
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Frozen Soils
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Spatially-distributed frozen soils

• Soil node temperatures solved via heat diffusion
  equation
• Ice content, infiltration rate and heat capacity
  calculated at nodes
• Assumed uniform temperature distribution across
  the grid cell allows spatial variation of
  infiltration capacity

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SWE and active layer depth, Alaska Coastal Plain
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Change in annual sensible heat flux with and
without frozen soils parameterization in the Ob
river basin
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Effect on runoff baseflow
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Lakes and Wetlands
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Predicting the effects of lakes and wetlands

• Lake energy balance based on
• Hostetler and Bartlein (1990)
• Hostetler (1991)
• Assumptions
• One effective lake for each grid cell
• Laterally-averaged temperatures and

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Lake energy balance
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Lake surface energy balance
Mean daily values, June-August 2000
Mean diurnal values, June-August 2000
Lake 1, Arctic Coastal Plain, Alaska
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Wetland Algorithm
soil saturated
land surface runoff enters lake evaporation
depletes soil moisture
lake recharges soil moisture
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Saturated extent 1999 and 2000
a.
b.
c.
d.
e.
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Simulated mean annual evaporationPutuligayuk
River

• Simulated annual evaporation increases by 60

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Blowing Snow
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Non-equilibrium Transport
snow
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Estimating average fetch
vegetation type
terrain slope
terrain st. dev
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Distribution of terrain slopes
Trail Valley Creek, NWT
Imnavait Creek, Alaska
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Simulated annual sublimation from blowing
snowSensitivity to fetch
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Sensitivity to vapor pressure
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Sublimation and melt as a fraction of maximum
snow water equivalent in the Ob River basin
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Conclusions

• Lakes and wetlands, freezing soils, and snow
  redistribution and sublimation are key hydrologic
  processes in the arctic, proper representation of
  which is critical to pan-arctic hydrologic
  prediction
• Lake and wetland effects can be substantially
  underestimated by standard land classification
  maps
• Sublimation and blowing snow effects at high
  latitude are critically dependent on surface
  roughness, and near-surface humidity, both of
  which have inherent estimation difficulties
• Frozen soil effects (e.g. active layer depth and
  timing) seem to be captured reasonably well in
  point simulations, but spatial variability and
  its parameterization at large scales remains
  unresolved