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Propagate a known spectrum to any other depth(s) (bidirectional).

Source: R/depth_propagation.R
propagate_spectrum.Rd

Applies Beer-Lambert attenuation at each wavelength independently, propagating a known spectral irradiance from depth from to one or more target depths to. Works in both directions: set to < from to recover a shallower (or surface) spectrum from a deeper measurement, assuming a homogeneous water column.

Usage

propagate_spectrum(E_lambda, ...)

# S3 method for class 'numeric'
propagate_spectrum(
  E_lambda,
  Kd_lambda,
  from = 0,
  to,
  format = c("long", "matrix"),
  lambda = NULL,
  allow_above_surface = FALSE,
  ...
)

# S3 method for class 'lux_spectrum'
propagate_spectrum(
  E_lambda,
  Kd_lambda,
  from = 0,
  to,
  allow_above_surface = FALSE,
  ...
)

Arguments

E_lambda

Spectral irradiance at depth from. Length-N vector or a lux_spectrum object.

...

Ignored.

Kd_lambda

Finite, non-negative diffuse attenuation coefficients (1/m). Length-N vector.

from

Finite scalar depth of the known spectrum in metres. Default 0.

to

Finite target depth(s) in metres. Scalar or vector.

format

"long" (default) or "matrix". Ignored for lux_spectrum input.

lambda

Optional wavelength values (nm) for long-format output.

allow_above_surface

Logical; permits negative absolute depths. Default FALSE.

Value

A data frame, matrix, or named list of lux_spectrum.

Details

This is the package's principal lightweight propagation tier. It applies \(E(z,\lambda) = E(z_0,\lambda) \exp[-K_d(\lambda)(z-z_0)]\), assuming \(K_d\) is constant along the path and wavelengths propagate independently. It does not model an angular radiance field, multiple scattering, or spectral redistribution. There is no universal supported depth range: validity depends on whether the supplied \(K_d\) represents the entire path. Bundled Jerlov data are limited to 350–700 nm. Inverse propagation is an assumption-heavy reconstruction that amplifies noise.

References

Kirk JTO (1994) Light and Photosynthesis in Aquatic Ecosystems, 2nd edn. Cambridge University Press.

Examples

E_10m <- c(8, 15, 20)
Kd    <- c(0.02, 0.06, 0.25)
propagate_spectrum(E_10m, Kd, from = 10, to = c(0, 25, 50))
#>   depth lambda            E
#> 1     0      1 9.771222e+00
#> 2     0      2 2.733178e+01
#> 3     0      3 2.436499e+02
#> 4    25      1 5.926546e+00
#> 5    25      2 6.098545e+00
#> 6    25      3 4.703549e-01
#> 7    50      1 3.594632e+00
#> 8    50      2 1.360769e+00
#> 9    50      3 9.079986e-04