vSmartMOM

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surface field (in radiative_transfer) ​

The bidirectional reflectance (BRDF) at the lower boundary, one per spectral band. Each entry is a constructor-call-shaped string parsed safely (no eval — a small whitelist of constructors).

Field signature ​

yaml
radiative_transfer:
  surface:
    - "<surface_constructor>"   # one entry per spec_band

The surface vector must have the same length as spec_bands.

Allowed constructors ​

Lambertian (m=0 only — diffuse, no Fourier dependence) ​

ConstructorUse case
LambertianSurfaceScalar(albedo::Real)Single albedo for all spectral points in the band. The simplest BRDF. Phase C trait: m_max = 0.
LambertianSurfaceSpectrum([albedos...])Vector of albedos, one per spectral point in the band. Use when the surface albedo varies appreciably across the band (e.g. snow in NIR).
LambertianSurfaceLegendre([a₀, a₁, a₂, ...])Legendre expansion in the spectral band's normalized coordinate.
LambertianSurfaceSpline(λ, ρ)Spline through tabulated (λ, ρ) pairs. For full spectral coverage use the LambertianSurfaceSpline helper directly in Julia rather than YAML.

Vegetation BRDFs (full Fourier; trait: m_max = user_l_cap) ​

ConstructorSourceUse case
rpvSurfaceScalar(ρ₀, ρ_c, k, Θ)Rahman-Pinty-VerstraeteVegetation BRDF; common in canopy retrievals.
RossLiSurfaceScalar(fvol, fgeo, fiso)Roujean / WannerMODIS BRDF kernel decomposition. Three-parameter linear model.

Ocean (full Fourier + sun-glint; trait: m_max = user_l_cap) ​

ConstructorUse case
CoxMunkSurface(wind_speed=U, n_water=...)Cox-Munk wave-slope statistics + Fresnel + (optional) whitecaps + Smith shadowing. Full polarization.

CoxMunkSurface keyword arguments:

  • wind_speed (required, m/s) — 10 m wind. Drives the Cox-Munk variance via Cox & Munk (1954) σ² = 0.003 + 0.00512·U.

  • n_water — complex refractive index. Default nothing triggers the built-in Segelstein 1981 spectral lookup.

  • whitecap_albedo (default 0.22) — Lambertian whitecap albedo (Koepke 1984).

  • include_whitecaps (default true) — whether to include the whitecap-fraction Lambertian addend.

  • shadowing (default true) — Smith (1967) shadow masking.

Composite (canopy + soil) ​

CanopySurface is configured via a top-level canopy: block, not as a string in surface:. The parser wraps each band's surface entry as the soil BRDF inside the canopy when canopy: is present. See Schema/canopy.md (forthcoming).

Examples ​

Lambertian land ​

yaml
radiative_transfer:
  spec_bands: ["[18867 18870]"]
  surface:    ["LambertianSurfaceScalar(0.05)"]

Cox-Munk ocean, default Segelstein water ​

yaml
radiative_transfer:
  spec_bands: ["[18867 18870]"]
  surface:    ["CoxMunkSurface(wind_speed=5.0)"]

Multiband (one BRDF per band) ​

yaml
radiative_transfer:
  spec_bands:
    - "[20000 20003]"
    - "[12500 12503]"
  surface:
    - "LambertianSurfaceScalar(0.05)"
    - "LambertianSurfaceScalar(0.40)"   # higher NIR albedo for soil

Phase C trait dispatch ​

Each surface declares its component_m_max:

Surfacecomponent_m_max(::T, ctx)
LambertianSurface*0 (m=0 is exact)
CoxMunkSurfacectx.user_l_cap (no scheme-imposed cap)
rpvSurfaceScalar / RossLiSurfaceScalarctx.user_l_cap
CanopySurfacectx.user_l_cap

A Cox-Munk + Lambertian band loops to the user-set stream_l_cap; a Lambertian-only Rayleigh band loops only to m=0:2 (Rayleigh trait = 2). See docs/dev_notes/fourier_stream_resolution_plan.md for the full trait table.

See also ​