R_abs: total absorbed radiation (W / m^2)

.get_Rabs(pars, unitless)

Arguments

pars	Concatenated parameters (`leaf_par`, `enviro_par`, and `constants`)
unitless	Logical. Should function use parameters with `units`? The function is faster when FALSE, but input must be in correct units or else results will be incorrect without any warning.

Value

Value in W / m$^2$ of class units

Details

The following treatment follows Okajima et al. (2012):

$$R_\mathrm{abs} = \alpha_\mathrm{s} (1 + r) S_\mathrm{sw} + \alpha_\mathrm{l} \sigma (T_\mathrm{sky} ^ 4 + T_\mathrm{air} ^ 4)$$

The incidient longwave (aka thermal infrared) radiation is modeled from sky and air temperature $\sigma (T_\mathrm{sky} ^ 4 + T_\mathrm{air} ^ 4)$ where $T_\mathrm{sky}$ is function of the air temperature and incoming solar shortwave radiation:

$$T_\mathrm{sky} = T_\mathrm{air} - 20 S_\mathrm{sw} / 1000$$

Symbol	R	Description	Units	Default
$\alpha_\mathrm{s}$	`abs_s`	absorbtivity of shortwave radiation (0.3 - 4 $\mu$m)	none	0.80
$\alpha_\mathrm{l}$	`abs_l`	absorbtivity of longwave radiation (4 - 80 $\mu$m)	none	0.97
$r$	`r`	reflectance for shortwave irradiance (albedo)	none	0.2
$\sigma$	`s`	Stephan-Boltzmann constant	W / (m$^2$ K$^4$)	5.67e-08
$S_\mathrm{sw}$	`S_sw`	incident short-wave (solar) radiation flux density	W / m$^2$	1000
$S_\mathrm{lw}$	`S_lw`	incident long-wave radiation flux density	W / m$^2$	calculated
$T_\mathrm{air}$	`T_air`	air temperature	K	298.15
$T_\mathrm{sky}$	`T_sky`	sky temperature	K	calculated

References

Okajima Y, H Taneda, K Noguchi, I Terashima. 2012. Optimum leaf size predicted by a novel leaf energy balance model incorporating dependencies of photosynthesis on light and temperature. Ecological Research 27: 333-46.

Examples