Vic model status blowing snow and lake algorithms
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VIC Model Status Blowing Snow and Lake Algorithms. Princeton Meeting December 4, 2006. Blowing Snow. Günter Eisenhardt 3.31.2002, Iceland. Snow accumulation. SWE > 0?. Blowing snow sublimation. Snow mass and energy balance. Yes. No.

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Vic model status blowing snow and lake algorithms l.jpg

VIC Model StatusBlowing Snow and Lake Algorithms

Princeton Meeting

December 4, 2006


Blowing snow l.jpg
Blowing Snow

Günter Eisenhardt 3.31.2002, Iceland


Predictive model of the sublimation from blowing snow l.jpg

Snow

accumulation

SWE > 0?

Blowing

snow

sublimation

Snow mass

and

energy balance

Yes

No

Predictive model of the sublimation from blowing snow

  • Derived from existing small-scale blowing snow models (Pomeroy et al. 1993 and Liston and Sturm 1998).

  • Mass concentration of suspended transport based on power law relationship (Kind 1992).

  • Particle sublimation rate proportional to the undersaturation of water vapor.

= VIC snow model


Distribution of terrain slopes l.jpg
Distribution of terrain slopes

Trail Valley Creek, NWT

Imnavait Creek, Alaska


Non equilibrium transport l.jpg

transport = 0

transport = Qt(x= f)

average fetch, f

Non-equilibrium Transport

snow




Slide8 l.jpg

  • Soil node temperatures solved via heat diffusion equation (Cherkauer and Lettenmaier 1999)

  • Constant flux or constant temperature options

  • Imposed temperature distribution at each node allows spatial variation of infiltration capacity and active layer depth across the grid cell (Cherkauer et al. 2001)


Imnavait creek active layer depth l.jpg
Imnavait Creek active layer depth (Cherkauer and Lettenmaier 1999)


Betty pingo swe and active layer depth l.jpg
Betty Pingo SWE and active layer depth (Cherkauer and Lettenmaier 1999)


On going work at uw l.jpg
On-going work at UW (Cherkauer and Lettenmaier 1999)

  • Confirmed functionality of constant flux solution

  • Revise distribution of soil thermal nodes to improve stability

  • Introduce ground ice parameterization


Lakes and wetlands l.jpg
Lakes and wetlands (Cherkauer and Lettenmaier 1999)

Source: San Diego State University Global Change Research Group


Predicting the effects of lakes and wetlands l.jpg
Predicting the effects of lakes and wetlands (Cherkauer and Lettenmaier 1999)

  • Lake energy balance based on:

    • Hostetler and Bartlein (1990)

    • Hostetler (1991)

  • Lake ice cover (Patterson and Hamblein)

  • Assumptions:

    • One “effective” lake for each grid cell;

    • Laterally-averaged temperatures.


Lake energy balance l.jpg
Lake energy balance (Cherkauer and Lettenmaier 1999)


Lake surface energy balance l.jpg

Mean daily values, June-August 2000 (Cherkauer and Lettenmaier 1999)

Lake surface energy balance

Mean diurnal values, June-August 2000

‘Lake 1’, Arctic

Coastal Plain, Alaska


Observed simulated l.jpg

Mean temperature profile (1993-1997) (Cherkauer and Lettenmaier 1999)Toolik Lake, Alaska

ObservedSimulated


Wetland algorithm l.jpg

soil (Cherkauer and Lettenmaier 1999)

saturated

land surface runoff & baseflow enters lake

evaporation depletes soil moisture

lake recharges soil moisture

Wetland Algorithm


Simulated saturated extent putuligayuk river alaska l.jpg
Simulated saturated extent (Cherkauer and Lettenmaier 1999)Putuligayuk River, Alaska


History l.jpg
History (Cherkauer and Lettenmaier 1999)

  • Original model - documented (briefly) in Cherkauer et al. (2003)

  • Subsequent revisions (incorporated into VIC 4.1.0 r3 and documented in Bowling et al. manuscript):

    • Lakes can disappear/reappear

    • Lake profile description and thermal solution nodes separated

    • Lake runoff rate more physically described


Current efforts l.jpg
Current Efforts (Cherkauer and Lettenmaier 1999)


Water table l.jpg

Water Table (Cherkauer and Lettenmaier 1999)

Previously VIC did not calculate the water table depth

Average depth to water table calculated for each vegetation type

Summation of depth of saturated layers and depth of excess soil moisture for unsaturated layer


Slide23 l.jpg

Wetland fraction (const) (Cherkauer and Lettenmaier 1999)

Upland fraction

(variable)

Lake fraction

(variable)

lake

h


Slide24 l.jpg

Wetland fraction (const) (Cherkauer and Lettenmaier 1999)

Upland fraction

(variable)

Lake fraction

(variable)

lake

h


Vic simulations l.jpg

Observations show rain pulse penetrating to water table quickly

Issue of moisture transfer to depth?

or

Lateral inflow from flooded ditch?

VIC Simulations

Observations

VIC top layer moisture

VIC 2nd layer moisture

VIC water table


Lateral exchange l.jpg

Lateral Exchange quickly

Previously the lake could not recharge the local groundwater

Equilibrium soil moisture is calculated to determine flow direction

Baseflow can go either into or out of the lake in a given time step

Baseflow out of lake is at maximum rate


Slide27 l.jpg

Equilibrium Soil Moisture quickly

Soil Moisture State

lake

lake

h


Lake extent l.jpg
Lake Extent quickly

  • Previously, maximum water extent fixed by inputs

    • elevation curve supplied for this wetland fraction only

    • emerging land had static characteristics

    • never worked with snow bands

  • Wetland now considered a subset of each vegetation type

    • Same elevation curve applies to all vegetation classes?

    • Lake area can be calculated separately for each veg class, or collapsed back to one effective lake

    • Could be a nightmare to calibrate


Lake extent scenarios l.jpg

Three scenarios defined: quickly

Variable extent/defined maximum, e.g. as defined by Bowling et al. (2002)

Constant extent, as used by Su et al. (2005)

Variable extent/unlimited growth

Maximum depth adjusted such that scenarios 1 and 2 have equal volume

Lake extent scenarios

Fractional Depth

Grid Cell

Fractional Area


Change in open water extent l.jpg

Scenario 1 quickly

Scenario 2

Scenario 3

Change in open water extent


Sub lake energy exchange l.jpg
Sub-Lake Energy Exchange quickly

  • Previously, heat fluxes in the soil below the lake were not resolved

    • Normal VIC implementation for exposed wetland soil (these are values output)

  • Appropriate soil heat flux algorithm called for sub-lake soil

    • Assumes that soil layers are preserved under the lake

    • When lake reaches a threshold depth, energy balance must be solved for combined water/soil layer for stability


What else l.jpg
What else? quickly

  • Photosynthesis – based ET scheme?

  • Groundwater parameterization

  • Permafrost runoff scheme