FAO56 (version 1.0)

SolRad: 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
)

Value

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

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)

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.

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.

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")