SolRad {FAO56}

Solar Radiation (R_s)

Description

SolRad returns the value of solar radiation.

Usage

SolRad(
  n = NULL,
  N = NULL,
  a_s = 0.25,
  b_s = 0.5,
  R_a,
  T_max = NULL,
  T_min = NULL,
  region = NULL
)

Arguments

n

Optional. A numeric scalar that denotes actual duration of sunshine [hour]

N

Optional. A numeric scalar that denotes maximum possible duration of sunshine or daylight hours [hour]

a_s

Optional. A numeric scalar that denotes regression constant, expressing the fraction ofextraterrestrial radiation reaching the earth on overcast days (n = 0). The default is a_s = 0.25.

b_s

Optional. A numeric scalar that denotes fraction of extraterrestrial radiation reaching the earth on clear days (n = N). The default is b_s = 0.5

R_a

A numeric scalar that denotes extraterrestrial radiation [MJ/(m^2\times day)]

T_max

Optional. A numeric scalar that denotes the daily maximum temperature [C].

T_min

Optional. A numeric scalar that denotes the daily minimum temperature [C].

region

A character string that introduce the type of region and can be assigned "inter" for interior locations and "coast" for coastal locations for Hargreaves radiation formula (alternative)

Details

This is a function to calculate the solar radiation based on the land type. If one of the arguments n or N is missing, the function needs to use the values of the arguments T_min, T_max, and region. If calibrated values of a_s and b_s are available, they can replace the default values.

Value

The function returns the value of solar radiation based as a numeric scalar.

Reference

Allen, R. G., Pereira, L. S., Raes, D., & Smith, M. (1998). Crop evapotranspiration - Guidelines for computing crop water requirements - FAO Irrigation and drainage paper 56. Fao, Rome, 300(9), D05109.

See Also

ExRad.

Examples

SolRad(n = 7.1, N = 10.9, R_a = 25.1)
SolRad(R_a = 25.1, T_max = 30, T_min = 20, region = "inter")