SiB Model

The SiB model provides a link between these two groups that allows plants to interact with changing atmospheric conditions, and these atmospheric conditions are determined, in part, by the role of vegetation in governing evaporation, absorption of solar radiation, interception of precipitation, etc. SiB allows for two-way interactions between the atmosphere and the biosphere/lithosphere.

1. Radiation absorption
   Plants in SiB absorb energy very effectively in the wavelength interval 0.4 to 0.72 microns (the photosynthetically active radiation, or PAR, portion of the solar spectrum).
   Plants in SiB reflect radiation in the near infrared portion of the spectrum.
   Bare ground in SiB has a gradual increase in reflection with wavelength from 0.4 to 4.0 microns.
2. Biophysical control of evapotranspiration
   Stomates ( timy openings in plant leaves) control the interchange of water and CO₂ between the atmosphere and the plant.
   Vegetation canopies intercept and hold precipitation and dew, which lowers water input to the soil and enhances evaporation.
3. Momentum transfer
   Plants create "friction" for the atmospheric flow near the surface. Plants create turbulent motions that enhance vertical mixing of heat and water vapor near the surface.
4. Soil moisture availability
   Plants in SiB have roots that determine the amount of water available for evapotranspiration.
5. Insulation
   SiB has live plants that shade the surface and protect it from intense solar radiation and strong evaporation.

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