radiation_julianDay: Solar radiation utility functions

Description

Set of functions used in the calculation of incoming solar radiation and net radiation.

Usage

radiation_julianDay(year, month, day)
radiation_dateStringToJulianDays(dateStrings)
radiation_solarDeclination(J)
radiation_solarConstant(J)
radiation_sunRiseSet(latrad, slorad, asprad, delta)
radiation_solarElevation(latrad, delta, hrad)
radiation_daylength(latrad, slorad, asprad, delta)
radiation_daylengthseconds(latrad, slorad, asprad, delta)
radiation_potentialRadiation(solarConstant, latrad, slorad, asprad, delta)
radiation_solarRadiation(
  solarConstant,
  latrad,
  elevation,
  slorad,
  asprad,
  delta,
  diffTemp,
  diffTempMonth,
  vpa,
  precipitation
)
radiation_directDiffuseInstant(
  solarConstant,
  latrad,
  slorad,
  asprad,
  delta,
  hrad,
  R_s,
  clearday
)
radiation_directDiffuseDay(
  solarConstant,
  latrad,
  slorad,
  asprad,
  delta,
  R_s,
  clearday,
  nsteps = 24L
)
radiation_skyLongwaveRadiation(Tair, vpa, c = 0)
radiation_outgoingLongwaveRadiation(
  solarConstant,
  latrad,
  elevation,
  slorad,
  asprad,
  delta,
  vpa,
  tmin,
  tmax,
  R_s
)
radiation_netRadiation(
  solarConstant,
  latrad,
  elevation,
  slorad,
  asprad,
  delta,
  vpa,
  tmin,
  tmax,
  R_s,
  alpha = 0.08
)

Value

Values returned for each function are:

radiation_dateStringToJulianDays: A vector of Julian days (i.e. number of days since January 1, 4713 BCE at noon UTC).
radiation_daylength: Day length (in hours).
radiation_daylengthseconds: Day length (in seconds).
radiation_directDiffuseInstant: A vector with instantaneous direct and diffusive radiation rates (for both SWR and PAR).
radiation_directDiffuseDay: A data frame with instantaneous direct and diffusive radiation rates (for both SWR and PAR) for each subdaily time step.
radiation_potentialRadiation: Daily (potential) solar radiation (in MJ·m-2).
radiation_julianDay: Number of days since January 1, 4713 BCE at noon UTC.
radiation_skyLongwaveRadiation: Instantaneous incoming (sky) longwave radiation (W·m-2).
radiation_outgoingLongwaveRadiation: Daily outgoing longwave radiation (MJ·m-2·day-1).
radiation_netRadiation: Daily net solar radiation (MJ·m-2·day-1).
radiation_solarConstant: Solar constant (in kW·m-2).
radiation_solarDeclination: Solar declination (in radians).
radiation_solarElevation: Angle of elevation of the sun with respect to the horizon (in radians).
radiation_solarRadiation: Daily incident solar radiation (MJ·m-2·day-1).
radiation_sunRiseSet: Sunrise and sunset hours in hour angle (radians).

Arguments

year, month, day: Year, month and day as integers.
dateStrings: A character vector with dates in format "YYYY-MM-DD".
J: Julian day (integer), number of days since January 1, 4713 BCE at noon UTC.
latrad: Latitude (in radians North).
slorad: Slope (in radians).
asprad: Aspect (in radians from North).
delta: Solar declination (in radians).
hrad: Solar hour (in radians).
solarConstant: Solar constant (in kW·m-2).
elevation: Elevation above sea level (in m).
diffTemp: Difference between maximum and minimum temperature (ºC).
diffTempMonth: Difference between maximum and minimum temperature, averaged over 30 days (ºC).
vpa: Average daily vapor pressure (kPa).
precipitation: Precipitation (in mm).
R_s: Daily incident solar radiation (MJ·m-2).
clearday: Boolean flag to indicate a clearsky day (vs. overcast).
nsteps: Number of daily substeps.
Tair: Air temperature (in degrees Celsius).
c: Proportion of sky covered by clouds (0-1).
tmin, tmax: Minimum and maximum daily temperature (ºC).
alpha: Surface albedo (from 0 to 1).

Functions

radiation_dateStringToJulianDays(): Date string to julian days
radiation_solarDeclination(): solar declination
radiation_solarConstant(): solar constant
radiation_sunRiseSet(): sun rise and set
radiation_solarElevation(): solar elevation
radiation_daylength(): Day length
radiation_daylengthseconds(): Day length seconds
radiation_potentialRadiation(): Potential radiation
radiation_solarRadiation(): solar Radiation
radiation_directDiffuseInstant(): Direct diffuse instant
radiation_directDiffuseDay(): Direct diffuse day
radiation_skyLongwaveRadiation(): Sky longwave radiation
radiation_outgoingLongwaveRadiation(): Outgoing longwave radiation
radiation_netRadiation(): Net radiation

Author

Miquel De Cáceres Ainsa, CREAF

References

Danby, J. M. Eqn. 6.16.4 in Fundamentals of Celestial Mechanics, 2nd ed. Richmond, VA: Willmann-Bell, p. 207, 1988.

Garnier, B.J., Ohmura, A., 1968. A method of calculating the direct shortwave radiation income of slopes. J. Appl. Meteorol. 7: 796-800

McMahon, T. A., M. C. Peel, L. Lowe, R. Srikanthan, and T. R. McVicar. 2013. Estimating actual, potential, reference crop and pan evaporation using standard meteorological data: a pragmatic synthesis. Hydrology & Earth System Sciences 17:1331–1363. See also: http://www.fao.org/docrep/x0490e/x0490e06.htm.

Reda, I. and Andreas, A. 2003. Solar Position Algorithm for Solar Radiation Applications. 55 pp.; NREL Report No. TP-560-34302, Revised January 2008. http://www.nrel.gov/docs/fy08osti/34302.pdf

Spitters, C.J.T., Toussaint, H.A.J.M. and Goudriaan, J. (1986). Separating the diffuse and direct components of global radiation and its implications for modeling canopy photosynthesis. I. Components of incoming radiation. Agricultural and Forest Meteorology, 38, 231–242.