Ian Baker

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Ian Baker Colorado State University Department of
Atmospheric Science/GDPE
With help from Ken Davis PSU Vince Gutschick,
Connie Maxwell, Mario Montes-Helu, Erika
Mortenson, Alonzo Soto, Felicia Najera, and Erik
Jackson NMSU Joe Berry, Bob Haxo, Carnegie
Institute of Washington A. Scott Denning, Neil
Suits, Niall Hanan CSU
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Motivation/Background

• Comparison of model results (SiB) to observations
• Ewers et al (2002) - transpiration calculated
  from sap flux data
• Vince Gutshick observations (LI-6200) at the
  leaf level (i.e. stomatal control, carboxylation
  capacity)
• Joe Berry provided a suite of programs that can
  derive SiB-type vegetation parameters from
  leaf-level observations

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The Model SiB2

• Simple Biosphere Model, version 2 (SiB2)
• Sellers et al. 1996
• Biophysical land surface model
• Describes heat, water and carbon transfers
• in the soil, vegetation, atmosphere
  continuum
• Developed for general circulation models
• Useful at many scales, globe to point
• Single canopy layer scheme
• Highly non-linear
• Large number of input parameters

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• SiB Vegetation Params
• 20 time-invariant biome-specific variables
• 13 soil properties (moisture, thermal and
  respiration)
• 8 NDVI-derived time-varying phenological
  variables (heterogeneous in space)

In SiB, WLEF site is mixed forest-biome 3. All
biome 3 sites are parameterized identically wrt
time-invariant properties
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SiB Time-Invariant Parameters

• Canopy height
• Vegetation fractional cover
• Leaf angle distribution
• Transmittance/reflectance
• Rubisco velocity of sun-leaf
• Quantum efficiency (C3/C4)
• BB slope/intercept
• Coupling parameters for eqn Amin(?c,?e,?s)
• Low-and high-temperature inhibition functions
• Canopy respiration factors
• Respiration fraction of Vmax

• These are the variables that we can adjust
• Vmax0
• BB slope
• BB intercept
• respcp
• hhti
• atheta

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PROCEDURE

• Sort Vince Gutschicks leaf-level obs by species
• Obtain species-specific values of
• Vmax0 maximum rubisco velocity
• binter BB intercept
• gradm BB slope
• respcp autotrophic respiration component
• hhti ½ point high-temp inhibition function
• atheta rubisco/light coupling factor
• Create a new SiB vegetation parameter file using
  these new values
• Run SiB

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Data from Ewers et al, 2002
Red pine Jack pine
White cedar Balsam fir Speckled alder
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Obs data asymptotes slightly above 3.0
OBS trembling aspen, balsam fir MODEL trembling
aspen, balsam fir Comparison looks quite good
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Obs data asymptotes near 2.0
OBS red pine, Jack pine MODEL Balsam fir,
spruce
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Obs data asymptotes near 2.0
OBS dominated by white cedar, also balsam fir,
speckled alder MODEL balsam fir, speckled alder
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Obs asymptote near 1.0
OBS sugar maple MODEL sugar maple
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SOME QUESTIONS

• Is it reasonable to create species-specific model
  vegetation for certain parameters, when a
  number of them, including
• aparc-canopy absorbed PAR
• LAI
• roughness length
• leaf projection
• are determined from canopy-level NDVI
  observations?
• Are the values I obtained internally consistent
  for each of the species I investigated?

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SOME MORE QUESTIONS

• Does this approach have the potential to lead to
  better simulation of fluxes of carbon, heat and
  moisture?
• Is there potential to utilize this approach in
  coupling SiB to mesoscale model(s) (RAMS)?
• Will higher-resolution information (both on the
  species and spatial/satellite scale) make
  species-specific land-atmosphere modeling more
  attractive?
• Is the technique Ive outlined adequate, or do
  the SiB parameters need to be made more fully
  self-consistent by including more parameters
  for each species?