Atmospheric Properties Changes by SiB

Atmospheric Properties Changed by SiB

Here we describe the terms from the atmospheric model that are changed by SiB and the properties of the plants and surface that change and influence the atmospheric conditions.

a) Atmospheric variables given to SiB

  1. Temperature, vapor pressure, and wind speed.
    * variables represent grid-averaged values
    * temperature, Tr
    * water-vapor pressure, er
    * wind speed ur
  2. Radiation
    * Visible or PAR (< 0.72 microns, direct beam) Fs,b(0)
    * Visible or PAR (, 0.72 microns, diffuse) Fs,d(0)
    * Near infrared (0.72 - 4.0 microns, direct beam) ) Fn,b(0)
    * Near infrared (0.72 - 4.0 microns, diffuse) Fn,d(0)
    * Thermal infrared (> 4.0 microns, diffuse) Ft,d(0)
    Fs is absorbed for photosynthesis by the leaves, and Fn is primarily scattered. Some light arrives at the leaves, not directly from the solar beam but reflected (sometimes with multiple reflections) off other leaves or higher levels of the canopy.
  3. Precipitation
    GCMs or regional climate models calculate precipitation accumulated at the surface over the time step of the model ( a few minutes to a few hours).
b) Components of Sib that change atmospheric properties
  1. Two types of vegetation;
    * Trees and shrubs
    * Ground cover

    2. Roots are different for each type of vegetation
  2. Rooting zones:
    * Layer 1: upper thin layer which allows direct soil evaporation
    * Layer 2: has roots of annual plants that may grow down to the bottom of this layer with time; has tree and shrub roots at the bottom of this layer
    * Layer 3: this layer collects water that percolates slowly through to the ground water reservoir.
The different types of land surface that are considered in SiB are depicted in Figure 1a. Later versions of SiB have reduced the number of such categories, but other similar models have similar categories. The three-layer soil zone used by SiB2 is shown in Figure 1b.

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