sun2ppfd: Convert irradiance (W/m^2) to PPFD (umol/m^2/s)

In cdmuir/leafoptimizer: Optimize leaf traits to different environments in silico

Description

Convert irradiance (W/m^2) to PPFD (umol/m^2/s)

Convert PPFD (umol/m^2/s) to irradiance (W/m^2)

Usage

sun2ppfd(S_sw, f_par, E_q)

ppfd2sun(PPFD, f_par, E_q)

Arguments

S_sw	incident short-wave (solar) radiation flux density with units (W / m^2) of class units.
f_par	fraction of S_sw that is photosynthetic active radiation (PAR). Must be unitless value between 0 and 1.
E_q	energy per mole quanta. Value in kJ/mol of class units.
PPFD	Photosynthetic photon flux density in μmol quanta / (m^2 s) of class units.

Details

Shortwave radiation is (at first approximation) the sum of photosynthetically active radiation (PAR) and near-infrared radiation (NIR):

S_sw = S_par + S_nir

Most sources (e.g. Jones 2013) assume that S_nir = S_par for sunlight, so f_par = 0.5.

To convert PAR to PPFD, divide by the energy per mol quanta. Gutschick (2016) suggests ~220 kJ/mol quanta for PAR:

PPFD = S_par / E_q

Value

Value with units μmol / (m^2 s) of class units.

References

Jones HG. 2013. Plants and microclimate: a quantitative approach to environmental plant physiology. Cambridge University Press.

Gutschick VP. 2016. Leaf energy balance: basics, and modeling from leaves to Canopies. In Canopy Photosynthesis: From Basics to Applications (pp. 23-58). Springer, Dordrecht.

Examples

S_sw <- set_units(1000, "W/m^2")
f_par <- set_units(0.5)
E_q <- set_units(220, "kJ/mol")
sun2ppfd(S_sw, f_par, E_q)

cdmuir/leafoptimizer documentation built on Sept. 10, 2021, 7:28 p.m.