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Convert photon-count spectral irradiance to Watts/m^2/nm.

Source: R/n2W_spec_irradiance.R
n2W_spec_irradiance.Rd

Converts per-bin photon flux (photons m\(^{-2}\) s\(^{-1}\) nm\(^{-1}\), or molar equivalents) to energy-based spectral irradiance in W m\(^{-2}\) nm\(^{-1}\). The inverse operation is W2mol_spec_irradiance.

Usage

n2W_spec_irradiance(value, ...)

# S3 method for class 'numeric'
n2W_spec_irradiance(
  value,
  lambda,
  photonic = FALSE,
  molar_unit = "photons",
  ...
)

# S3 method for class 'lux_spectrum'
n2W_spec_irradiance(value, ...)

Arguments

value

Spectral irradiance in photons/m^2/s/nm (or molar units), or a lux_spectrum with a photonic irradiance or radiance unit.

...

Ignored.

lambda

Wavelength in nm for each bin.

photonic

Logical; if TRUE, value is in molar units (µmol, mmol, or mol/m²/s/nm) — specify which via molar_unit. Defaults to FALSE. Note: photonic = TRUE means raw photon counts in par_irradiance, and photon-or-molar units in irradiance2lux.

molar_unit

Molar unit string (e.g. "umol"). Defaults to "photons".

Value

Numeric vector of spectral irradiance in W/m^2/nm, or a lux_spectrum with unit = "W/m2/nm" or "W/m2/sr/nm" according to the input dimensionality.

Details

Each photon at wavelength \(\lambda\) carries energy \(E = hc/\lambda\). Spectral irradiance in W m\(^{-2}\) nm\(^{-1}\) is therefore the photon flux \(N\) (photons m\(^{-2}\) s\(^{-1}\) nm\(^{-1}\)) multiplied by the per-photon energy: $$E(\lambda) = N(\lambda) \cdot \frac{hc}{\lambda}$$ where \(h = 6.626 \times 10^{-34}\) J s (Planck constant) and \(c = 2.998 \times 10^8\) m s\(^{-1}\) (speed of light). The constant \(hc\) in nm-compatible units is \(1.98645 \times 10^{-16}\) J nm, the value used internally.

Examples

utils::data(Naples)
n2W_spec_irradiance(Naples$depth_0m, Naples$wv, photonic = TRUE, molar_unit = "umol")
#>   [1] 0.27424602 0.24126393 0.26762964 0.31135078 0.26569105 0.29119546
#>   [7] 0.23792557 0.25633630 0.27247262 0.32820588 0.42158393 0.40393943
#>  [13] 0.42836925 0.42618633 0.41625798 0.37786576 0.36771242 0.42164085
#>  [19] 0.44300894 0.45851513 0.47053821 0.46809339 0.46037631 0.45524011
#>  [25] 0.45399282 0.45868533 0.44936449 0.41334402 0.43362165 0.42308153
#>  [31] 0.40057142 0.40933521 0.39216767 0.35843778 0.38036506 0.37017866
#>  [37] 0.37030261 0.36910845 0.35720779 0.35476225 0.35104575 0.33837757
#>  [43] 0.33918030 0.32915501 0.32736576 0.32229470 0.32185370 0.29570239
#>  [49] 0.28632886 0.28988148 0.29048273 0.28946892 0.27970679 0.27613916
#>  [55] 0.27413115 0.26529430 0.26305895 0.26229405 0.25707661 0.24415329
#>  [61] 0.24171249 0.22855315 0.24248749 0.23947249 0.23476624 0.23148846
#>  [67] 0.22667883 0.19709924 0.19743193 0.20173409 0.19663048 0.20022861
#>  [73] 0.19727908 0.16200707 0.16070020 0.15656334 0.16882651 0.17589551
#>  [79] 0.17869892 0.17996372 0.17740950 0.15355273 0.08077991 0.14398860
#>  [85] 0.16386352 0.16316457 0.16107135 0.15499395 0.14896140 0.14727310
#>  [91] 0.14345521 0.14282245 0.12904936 0.11167420 0.11679813 0.12195687
#>  [97] 0.12017625 0.12716373 0.12856936 0.12640937 0.11644867 0.12297237
#> [103] 0.12395377