The function estimates the ratio of diffuse to direct solar radiation based on the approximation of the SOLRAD model (McCullough and Porter 1971) described in Tracy et al. (1983) .

proportion_diffuse_solar_radiation(psi, p_a, A)

Arguments

psi

numeric Zenith angle of the sun (degrees).

p_a

numeric Atmospheric pressure (kPa).

A

numeric albedo of the substrate (fraction of 1).

Value

numeric diffuse fraction.

References

McCullough EC, Porter WP (1971). “Computing Clear Day Solar Radiation Spectra for the Terrestrial Ecological Environment.” Ecology, 52(6), 1008-1015. doi:10.2307/1933806 .

Tracy CR, Hammond KA, Lechleitner RA, II WJS, Thompson DB, Whicker AD, Williamson SC (1983). “Estimating clear-day solar radiation: an evaluation of three models.” Journal of Thermal Biology, 8(3), 247-251. doi:10.1016/0306-4565(83)90003-7 .

Examples

  proportion_diffuse_solar_radiation(psi = 60, 
                                     p_a = 86.1, 
                                     A   = 0.25)
#> [1] 0.09352554