medfate (version 2.8.0)

light: Radiation transfer functions

Description

Functions light_layerIrradianceFraction and light_layerIrradianceFractionBottomUp calculate the fraction of above-canopy irradiance (and the soil irradiance, respectively) reaching each vegetation layer. Function light_layerSunlitFraction calculates the proportion of sunlit leaves in each vegetation layer. Function light_cohortSunlitShadeAbsorbedRadiation calculates the amount of radiation absorved by cohort and vegetation layers, while differentiating between sunlit and shade leaves.

Usage

light_layerIrradianceFraction(LAIme, LAImd, LAImx, k, alpha, 
                              trunkExtinctionFraction = 0.1)
light_layerIrradianceFractionBottomUp(LAIme, LAImd, LAImx, k, alpha, 
                              trunkExtinctionFraction = 0.1)
light_layerSunlitFraction(LAIme, LAImd, kb)
light_cohortSunlitShadeAbsorbedRadiation(Ib0, Id0, Ibf, Idf, beta,
                                         LAIme, LAImd,
                                         kb, kd, alpha, gamma)
light_instantaneousLightExtinctionAbsortion(LAIme, LAImd, LAImx,
                                            kPAR, alphaSWR, gammaSWR,
                                            ddd, ntimesteps = 24, 
                                            trunkExtinctionFraction = 0.1)
light_longwaveRadiationSHAW(LAIme, LAImd, LAImx, 
                            LWRatm, Tsoil, Tair, trunkExtinctionFraction = 0.1)
light_cohortAbsorbedSWRFraction(z, x, SpParams, gdd = NA)
light_PARground(x, SpParams, gdd = NA, mode = "MED")
light_SWRground(x, SpParams, gdd = NA, mode = "MED")
light_PARcohort(x, SpParams, gdd = NA, mode = "MED")

Value

Functions light_layerIrradianceFraction, light_layerIrradianceFractionBottomUp and light_layerSunlitFraction return a numeric vector of length equal to the number of vegetation layers. Function light_cohortSunlitShadeAbsorbedRadiation returns a list with two elements (matrices): I_sunlit and I_shade.

Arguments

LAIme

A numeric matrix of live expanded LAI values per vegetation layer (row) and cohort (column).

LAImd

A numeric matrix of dead LAI values per vegetation layer (row) and cohort (column).

LAImx

A numeric matrix of maximum LAI values per vegetation layer (row) and cohort (column).

k

A vector of light extinction coefficients.

kb

A vector of direct light extinction coefficients.

kd

A vector of diffuse light extinction coefficients.

Ib0

Above-canopy direct incident radiation.

Id0

Above-canopy diffuse incident radiation.

Ibf

Fraction of above-canopy direct radiation reaching each vegetation layer.

Idf

Fraction of above-canopy diffuse radiation reaching each vegetation layer.

alpha

A vecfor of leaf absorbance by species.

beta

Solar elevation (in radians).

gamma

Vector of canopy reflectance values.

kPAR

A vector of visible light extinction coefficients for each cohort.

alphaSWR

A vecfor of hort-wave absorbance coefficients for each cohort.

gammaSWR

A vector of short-wave reflectance coefficients (albedo) for each cohort.

ddd

A dataframe with direct and diffuse radiation for different subdaily time steps (see function radiation_directDiffuseDay in package meteoland).

ntimesteps

Number of subdaily time steps.

trunkExtinctionFraction

Fraction of extinction due to trunks (for winter deciduous forests).

LWRatm

Atmospheric downward long-wave radiation (W/m2).

Tsoil

Soil temperature (Celsius).

Tair

Canopy layer air temperature vector (Celsius).

x

An object of class forest

SpParams

A data frame with species parameters (see SpParamsMED).

z

A numeric vector with height values.

gdd

Growth degree days.

mode

Calculation mode, either "MED" or "US".

Author

Miquel De Cáceres Ainsa, CREAF

Details

Functions for short-wave radiation are adapted from Anten & Bastiaans (2016), whereas long-wave radiation balance follows Flerchinger et al. (2009). Vegetation layers are assumed to be ordered from bottom to top.

References

Anten, N.P.R., Bastiaans, L., 2016. The use of canopy models to analyze light competition among plants, in: Hikosaka, K., Niinemets, U., Anten, N.P.R. (Eds.), Canopy Photosynthesis: From Basics to Application. Springer, pp. 379–398.

Flerchinger, G. N., Xiao, W., Sauer, T. J., Yu, Q. 2009. Simulation of within-canopy radiation exchange. NJAS - Wageningen Journal of Life Sciences 57 (1): 5–15. https://doi.org/10.1016/j.njas.2009.07.004.

See Also

spwb

Examples

LAI = 2
nlayer = 10
LAIlayerlive = matrix(rep(LAI/nlayer,nlayer),nlayer,1)
LAIlayerdead = matrix(0,nlayer,1)
kb = 0.8
kd_PAR = 0.5
kd_SWR = kd_PAR/1.35
alpha_PAR = 0.9
gamma_PAR = 0.04
gamma_SWR = 0.05
alpha_SWR = 0.7

Ibfpar = light_layerIrradianceFraction(LAIlayerlive,LAIlayerdead,LAIlayerlive,kb, alpha_PAR)
Idfpar = light_layerIrradianceFraction(LAIlayerlive,LAIlayerdead,LAIlayerlive,kd_PAR, alpha_PAR)
Ibfswr = light_layerIrradianceFraction(LAIlayerlive,LAIlayerdead,LAIlayerlive,kb, alpha_SWR)
Idfswr = light_layerIrradianceFraction(LAIlayerlive,LAIlayerdead,LAIlayerlive,kd_SWR, alpha_SWR)
fsunlit = light_layerSunlitFraction(LAIlayerlive, LAIlayerdead, kb)
SHarea = (1-fsunlit)*LAIlayerlive[,1] 
SLarea = fsunlit*LAIlayerlive[,1] 

par(mar=c(4,4,1,1), mfrow=c(1,2))
plot(Ibfpar*100, 1:nlayer,type="l", ylab="Layer", 
     xlab="Percentage of irradiance", xlim=c(0,100), ylim=c(1,nlayer), col="dark green")
lines(Idfpar*100, 1:nlayer, col="dark green", lty=2)
lines(Ibfswr*100, 1:nlayer, col="red")
lines(Idfswr*100, 1:nlayer, col="red", lty=2)

plot(fsunlit*100, 1:nlayer,type="l", ylab="Layer", 
     xlab="Percentage of leaves", xlim=c(0,100), ylim=c(1,nlayer))
lines((1-fsunlit)*100, 1:nlayer, lty=2)


solarElevation = 0.67
SWR_direct = 1100
SWR_diffuse = 300
PAR_direct = 550
PAR_diffuse = 150


abs_PAR = light_cohortSunlitShadeAbsorbedRadiation(PAR_direct, PAR_diffuse,
                        Ibfpar, Idfpar, beta = solarElevation, 
                        LAIlayerlive, LAIlayerdead, kb, kd_PAR, alpha_PAR, gamma_PAR)
abs_SWR = light_cohortSunlitShadeAbsorbedRadiation(SWR_direct, SWR_diffuse,
                        Ibfswr, Idfswr, beta = solarElevation, 
                        LAIlayerlive, LAIlayerdead, kb, kd_SWR, alpha_SWR, gamma_SWR)
par(mar=c(4,4,1,1), mfrow=c(1,2))
absRadSL = abs_SWR$I_sunlit[,1]
absRadSH = abs_SWR$I_shade[,1]
lambda = 546.6507
QSL = abs_PAR$I_sunlit[,1]*lambda*0.836*0.01
QSH = abs_PAR$I_shade[,1]*lambda*0.836*0.01
plot(QSL, 1:nlayer,type="l", ylab="Layer", 
     xlab="Absorbed PAR quantum flux per leaf area", ylim=c(1,nlayer), col="dark green", 
     xlim=c(0,max(QSL)))
lines(QSH, 1:nlayer, col="dark green", lty=2)
plot(absRadSL, 1:nlayer,type="l", ylab="Layer", 
     xlab="Absorbed SWR per leaf area (W/m2)", ylim=c(1,nlayer), col="red", 
     xlim=c(0,max(absRadSL)))
lines(absRadSH, 1:nlayer, col="red", lty=2)