spctral2: SPCTRAL2 Solar Irradiance Model

In sean-rohan/trawllight: Derive apparent optical properties from trawl-mounted light sensors

SPCTRAL2 Solar Irradiance Model

Description

An R-based implementation of the Bird and Riordan (1984, 1986) SPCTRAL2 model. Produces estimates direct and diffuse spectral irradiance on horizontal and titled surfaces at the Earth's surface for 300-4000 nm wavelengths. This R implementation is based on code for the FORTRAN program SPCTRLA2, including corrections to code and equations described by Bird and Riordan (1986). As of July 2021, FORTRAN and C implementations of SPCTRAL2 using the original Bird and Riordan (1984, 1986) formulation is available from the National Renewable Energy Laboratory: [https://www.nrel.gov/grid/solar-resource/spectral.html](https://www.nrel.gov/grid/solar-resource/spectral.html).

Usage

spctral2(
  latitude,
  longitude,
  doy,
  hour,
  minute,
  alpha,
  angle_of_incidence,
  ozone = NA,
  albedo,
  surface_tilt,
  surface_azimuth = 180,
  surface_pressure,
  aod,
  water_vapor,
  asym = 0.65,
  omega = 0.945,
  omega_p = 0.095,
  cloud_modification = FALSE
)

Arguments

latitude	Latitude in decimal degrees (East is positive, West is negative)
longitude	Longitude in decimal degrees (North is positive, South is negative)
doy	Day of year (numeric vector of length 1 with a values of 1-365)
hour	Local hour
minute	Local minute
alpha	Power on angstrom turbidity expression (default = 1.14 for rural areas
angle_of_incidence	Angle of incidence of direct beam on flat surface (in degrees)
ozone	Ozone (O_3) in atmospheres per centimeter
albedo	Ground albedo. Default is a generic value of 0.06 for sea surface
surface_tilt	Tilt angle of ground surface from horizontal (degrees)
surface_azimuth	Aziumuth of surface
surface_pressure	Surface pressure (milibars)
aod	aerosol optical depth at 0.5 microns (base e)
water_vapor	precipitable water vapor (cm)
asym	Aerosol scattering asymmetry factor (forward to total scattering ratio)
omega	Single scattering albedo at 400 nm. Default = 0.945
omega_p	Single scattering wavelength variation factor. Default = 0.095
cloud_modification	Logical. Should the cloud cover modification from Bird et al. (1987) be used. Default = TRUE.

Value

A data frame containing spectral direct and diffuse irradiance by wavelength at the earth's surface.

Author(s)

Sean Rohan [e-mail]

References

Bird, R., Riordan, C. 1984. Simple solar spectral model for direct and diffuse irradiance on horizontal and titled planes at the Earth's surface for cloudless atmospheres. SERI/TR-2145-2436. Solar Energy Research Institute. 37 pp.

Bird, R.E., Riordan, C., 1986. Simple solar spectral model for direct and diffuse irradiance on horizontal and tilted planes at the Earth’s surface for cloudless atmospheres. J. Clim. Appl. Meteorol. 25, 87–97. https://doi.org/10.1175/1520-0450(1986)025<0087:SSSMFD>2.0.CO;2

sean-rohan/trawllight documentation built on Jan. 13, 2023, 10:43 p.m.