SiBD Carbon Model

SiB2 (version SiBDRV from Colorado State U.)

Authors

Originally developed by Peter Sellers, NASA Goddard Space Flight Center, Greenbelt, Maryland

Substantively modified by Scott Denning, Ian Baker, Niall Hanan, and others at Colorado State University

Links

http://www.cnr.berkeley.edu/~tdebiase/sib/

Description

The Simple Biosphere 2 (SiB2) model can simulate local and regional scale land-surface energy, momentum and mass fluxes using observed forcing ("off-line" mode), or serve as the land surface component of a General Circulation Model (GCM). Compared with other models, the strength of SiB2 is its vegetation modeling, with dynamic treatment of LAI based on remote-sensed imagery.

Model scale and resolution

Time-steps for integration are seconds. For historical (spin-up) runs, meteorology data are typically provided at 30-min. intervals. Model results can be provided with a high (seconds) or low (monthly) temporal resolution. The spatial scale of each model simulation is a local canopy, but global simulations can be made by providing separate inputs for each location in a grid. The SiB2 model was developed for integration with GCMs.

Precursors

SiB2 was developed as an improved version of the original Simple Biosphere model (SiB or SiB1) of Sellers et al (1986). Several improvements have been made. The response of stomatal conductance to environmental forcing in SiB2 is simpler and more realistic than that in SiB. Leaf-level photosynthesis and stomatal conductance values in SiB2 are now integrated to the canopy scale. SiB2 allows dynamic vegetation to be simulated driven by satellite-derived global data of vegetation phenology. The soil hydrological parameterization has been modified to give more-reliable calculations of inter-layer exchange within the soil profile. SiB2 simulates gradual changes in surface temperature and reflectance as the amount of snow varies.

Inputs

Climate variables

  1. Atmospheric boundary-layer temperature (degrees K)
  2. Atmospheric boundary-layer vapor pressure (Pa)
  3. Atmospheric boundary-layer wind speed (m/s)
  4. Atmospheric boundary-layer CO2 partial pressure (Pa)
  5. Atmospheric boundary-layer O2 partial pressure (Pa)
  6. Atmospheric boundary-layer reference height (m)
  7. Incident solar radiation, visible, near-infrared, diffuse, and beam (W/m2)
  8. Incident thermal infrared radiation (diffuse only) (W/m2)
  9. Convective precipitation rate (mm)
  10. Large-scale precipitation rate (mm)
  11. Atmospheric surface pressure (Pa)

Site variables

  1. Ground roughness length (m)
  2. Depth of surface soil layer (m)
  3. Total soil depth (m)
  4. Mean topographic slope (radians)
  5. Soil reflectance
  6. Soil water potential at saturation (m)
  7. Soil hydraulic conductivity at saturation (m/s)
  8. Soil wetness parameter
  9. Soil water content at saturation (porosity)

Lifeform variables

  1. Height of canopy top and bottom (m)
  2. Inflection height for leaf-area density (m)
  3. Canopy cover fraction
  4. Leaf-angle distribution factor
  5. Momentum transfer parameters
  6. Leaf width and length (m)
  7. Root depth (m)
  8. Leaf reflectance
  9. Leaf transmittance
  10. Max. rubisco capacity at top of canopy (mol/m2/s)
  11. Partial pressure of oxygen in leaf interior (Pa)
  12. Rubisco specificity for CO2 relative to O2
  13. Michaelis-Menton constant for CO2 (Pa)
  14. Inhibition constant for O2 (Pa)
  15. Intrinsic quantum efficiencies of C3, C4 photosynthesis
  16. Coupling coefficients
  17. Leaf respiration coefficient
  18. Stomatal slope factor
  19. Minimum stomatal conductance (mol/m2/s)
  20. Temperature inhibition parameters (K-1)
  21. Half-inhibition parameters for temp. (K) and water potential (m)

Time-varying variables

  1. Fraction of incident radiation absorbed by canopy (FPAR)
  2. Total leaf-area index (LAI)
  3. Canopy greenness fraction
  4. Canopy roughness length (m)
  5. Canopy zero plane displacement (m)
  6. Bulk boundary-layer resistance coefficient (s/m)1/2
  7. Ground to canopy air-space resistance coefficient
  8. Mean canopy extinction coefficient
  9. Canopy thermal infrared transmittance

Testing and validation

References

Sellers, P.J., D.A. Randall, G.J. Collatz, J.A. Berry, C.B. Field, D.A. Dazlich, C. Zhang, G.D. Collelo, and L. Bounoua, 1996. A revised land surface parameterization (SiB2) for atmospheric GCMs .1. Model formulation. Journal of Climate 9: 676.

Colello, G.D., C. Grivet, P.J. Sellers, and J.A. Berry. 1998. Modeling of energy, water, and CO2 flux in a temperate grassland ecosystem with SiB2: May-October 1987. Journal of the Atmospheric Sciences 55: 1141.

Cramer, W. and C.B. Field. 1999. Comparing global models of terrestrial net primary productivity (NPP): introduction. Global Change Biology 5: 3.

Cramer, W., D.W. Kicklighter, A. Bondeau, B. Moore, C. Churkina, B. Nemry, A. Ruimy, and A.L. Schloss. 1999. Comparing global models of terrestrial net primary productivity (NPP): overview and key results. Global Change Biology, 5: 1.

VEMAP members. 1995. Vegetation/ecosystem modeling and analysis project: Comparing biogeography and biogeochemistry models in a continental-scale study of terrestrial ecosystem responses to climate change and CO2 doubling. Global Biogeochemical Cycles 9(4): 407-437.


William W. Hargrove (hnw@fire.esd.ornl.gov)
Last Modified: Mon Aug 19 20:20:10 EDT 2002