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canopy block (optional) ​

Wraps each spectral band's existing radiative_transfer.surface BRDF as soil underneath a multi-layer vegetation canopy (CoreRT.CanopySurface), solved internally via adding-doubling before interacting with the atmospheric RT. The mere presence of this top-level block is what activates the wrapping — see Schema/surface.md § Composite (canopy + soil).

Parsed by _parse_canopy_section in src/IO/Parameters.jl.

Note on schema coverage ​

The JSON Schema at schemas/vsmartmom-parameters.schema.json currently declares canopy as additionalProperties: true with only a block-level description — none of the per-field validation or autocomplete below is wired into the schema yet. Field names and defaults on this page come from the parser and the CanopySurface constructor, not from the JSON Schema, so editor autocomplete (see Schema.md) will not catch a typo'd canopy: field name.

Fields ​

FieldTypeDefaultDescription
LAIReal3.0Total leaf area index.
n_layersInteger1Number of canopy sub-layers solved via adding-doubling internally (1 = big-leaf).
leaf_reflectanceReal or Vector{Real}0.4Leaf reflectance. Scalar or spectral vector on leaf_optics_grid.
leaf_transmittanceReal or Vector{Real}0.05Leaf transmittance. Scalar or spectral vector on leaf_optics_grid.
leaf_optics_gridVector{Real}nothing (scalar leaf optics)Wavelength/wavenumber grid matching spectral leaf_reflectance / leaf_transmittance. In YAML this is a plain numeric vector paired with grid_unit; built in Julia it can also be a Unitful vector (u"nm" / u"cm^-1").
grid_unitString"nm"Unit of leaf_optics_grid: "nm" or "cm_inv".
clumpingReal, String, or Dictnone (NoClumping)Canopy clumping factor. A bare number Ω → ConstantClumping(Ω); "none" → NoClumping(); {type: "chen_leblanc", Ω₀: .., c: .., e: ..} → ChenLeblancClumping. Affects the effective G-function used in propagation, not the Z-matrix normalization.
include_atmBoolfalseInclude within-canopy gas absorption between sub-layers.
canopy_dpReal [hPa]nothingPressure thickness of the within-canopy air column (e.g. 3.0 hPa ≈ 30 m forest). Only meaningful when include_atm: true.
soilString or "from_surface""from_surface"Soil BRDF underneath the canopy. "from_surface" reuses the band's existing radiative_transfer.surface entry as soil; otherwise a surface constructor string using the same vocabulary as Schema/surface.md.
n_leaf_quadratureIntegerCanopyOptics.CanopyQuadrature() defaultLeaf-angle quadrature point count (advanced; forwarded to CanopyOptics.CanopyQuadrature).
n_azimuth_quadratureIntegerCanopyOptics.CanopyQuadrature() defaultAzimuth quadrature point count (advanced; forwarded to CanopyOptics.CanopyQuadrature).

Not YAML-configurable (Julia-only, set by constructing CanopySurface directly): LAD (leaf-angle distribution; defaults to CanopyOptics.spherical_leaves()), canopy_scattering (defaults to a BiLambertianCanopyScattering built from the mean leaf_reflectance / leaf_transmittance), and lai_fractions (per-sub-layer LAI split; defaults to uniform). For PROSPECT-derived spectral leaf optics, build the surface in Julia with CanopySurface_from_prospect(leaf, λgrid; soil=..., LAI=...) instead of the YAML canopy: block (see the comment block in config/canopy_forest.yaml).

Outputs ​

The canopy layer folds the direct beam into its reflected source and sets its j₀⁺ = 0. The TOA radiance and the hdr / bhr_uw diagnostics include the canopy's reflection of the direct beam. bhr_dw, the hemispherical downwelling flux at the surface, is diffuse only for a canopy: the attenuated direct flux μ₀ F₀ e^{−τ/μ₀} that a bare surface adds to bhr_dw is absent. Add it yourself to form a canopy BHR (see Concepts/05 § HDRF and BHR). For the same reason the forward BOA downwelling radiance carries no collimated solar beam at a view that falls on the solar ordinate (a bare surface carries it there; the linearized solver adds it for every surface). Interior observer heights are not available with a canopy.

Example ​

Forest canopy over a dark Lambertian soil, with within-canopy absorption (config/canopy_forest.yaml):

yaml
radiative_transfer:
  spec_bands:
    - "[19417.0 19418.0]"
  surface:
    - LambertianSurfaceScalar(0.10)   # soil BRDF, wrapped by canopy below
  polarization_type: Stokes_IQUV()
  nstreams: 11
  truncation: NoTruncation()
  depol: -1
  float_type: Float64
  architecture: default_architecture

canopy:
  LAI: 5.0
  n_layers: 4
  leaf_reflectance: 0.45
  leaf_transmittance: 0.05
  include_atm: true
  canopy_dp: 3.0        # ~30 m forest ≈ 3 hPa

Full runnable scene: config/canopy_forest.yaml. Minimal test scene: test/test_parameters/CanopyTest.yaml.

See also ​