radtran: RADTRAN Solar Irradiance Model with delta-Eddington cloud...

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

RADTRAN Solar Irradiance Model with delta-Eddington cloud transmission

Description

An R-based implementation of the Gregg and Carder (1990) model for cloudless maritime atmospheres, along with an option to use the delta-Eddington approximation of two-stream approach for spectral cloud transmission following Slingo (1989). Produces estimates of direct and diffuse spectral irradiance at the sea surface and just below the sea surface at 1 nm resolution for 350-700 nm wavelengths. Atmospheric path length calculation (air mass) follows Kasten and Young (1989) for zenith angles up to 90 degrees. At zenith angles larger than 90 degrees atmospheric path lengths are calculated using Schoenberg's (1929) spherical approximation assuming an earth radius of 6371 km and atmosphere height of 9 km. Ozone can be user-specified or approximated following Van Heuklon (1979).

Usage

radtran(
  latitude,
  longitude,
  zenith_degrees = NULL,
  doy = NULL,
  hour = NULL,
  minute = NULL,
  alpha,
  surface_pressure,
  water_vapor = NA,
  aerosol_scale_height = NA,
  visual_range = NA,
  air_mass = NA,
  relative_humidity = NA,
  wind_speed = 0,
  cloud_modification = TRUE,
  cloud_droplet_radius = 11.8,
  liquid_water_path = 125,
  water_refraction = 1.341,
  foam_spectrum = FALSE,
  ozone = "vanheuklon",
  w_v = 350:700,
  e_v = NA
)

Arguments

latitude	Latitude in decimal degrees (East is positive, West is negative)
longitude	Longitude in decimal degrees (North is positive, South is negative)
zenith_degrees	Solar zenith angle in degrees. Pass either externally provided zenith_degrees or hour, and minute. Default = NULL.
doy	Day of year (numeric vector of length 1 with a values of 1-365).
hour	Local hour. Not used of zenith_degrees is provided.
minute	Local minute. Not used of zenith_degrees is provided.
alpha	Power on angstrom turbidity expression
surface_pressure	Surface pressure (milibars)
water_vapor	precipitable water vapor (cm)
aerosol_scale_height	Aerosol scale height in kilometers. Only used if cloud_modification = FALSE.
visual_range	Visibility in kilometers. Only used if cloud_modification = FALSE.
air_mass	Air mass type (1-10). Typically 1-10, where 1 correspondswith marine aerosols, 10 with continental aerosols.
relative_humidity	Relative humidity (percent).
wind_speed	Wind speed in meters per second. Must be greater than or equal to zero. Default = 0 (calm)
cloud_modification	Logical. Use the cloud cover modification from Gregg (2002), based on Slingo (1989)? Default = TRUE.
cloud_droplet_radius	Cloud droplet radius in micrometers. Used for cloud_modification. Default 11.8 micrometers = mean oceanic value from Han et al. (1994).
liquid_water_path	Liquid water path used for cloud_modification.
water_refraction	Refractive index of water. Default for seawater = 1.341.
foam_spectrum	Logical. TRUE = use Gregg (2002) wavelength-dependent correction for sea-foam reflectance-based on Frouin et al. (1996). FALSE = original implementation with no spectral dependence (Gregg and Carder 1990)
ozone	Either a 1L numeric vector indicating the total ozone value or a character vector indicating an algorithmic approximation method. The only approximation method currently available is "vanheuklon" based on Van Heuklon (1979).
w_v	Numeric vector indicating wavelengths to use. Default set to maximum range of 350:700
e_v	Optional. Numeric vector of top-of-atmosphere irradiances. If not provided, uses default 1-nm resolution solar TOA irradiance from Gregg and Carder (1990).
below_surface	Logical. TRUE = estimate irradiance just below the sea surface. FALSE = estimate irradiance just above the sea surface.

Value

A data frame containing spectral direct and diffuse irradiance by wavelength at the sea surface and just below the sea surface.

Author(s)

Sean Rohan [e-mail]

References

Gregg, W.W., 2002. A coupled ocean-atmosphere radiative model for global ocean biogeochemical models. NASA Global Modeling and Assimilation Series, M. Suarez (ed.), NASA Technical Memorandum 2002-104606, Volume 22.

Gregg, W.W., Carder, K.L., 1990. A simple spectral solar irradiance model for cloudless maritime atmospheres. Limnol. Oceanogr. 35, 1657–1675. https://doi.org/10.4319/lo.1990.35.8.1657

Kasten, F., 1965. A new table and approximation formula for the relative optial air mass. Arch. für Meteorol. Geophys. und Bioklimatologie Ser. B 14, 206–223. https://doi.org/10.1007/BF02248840

Kasten, F., Young, A.T., 1989. Revised optical air mass tables and approximation formula. Appl. Opt. 28, 4735–4738. https://doi.org/10.1364/AO.28.004735

Schoenberg, E. (1929). Theoretische Photometrie, g) Über die Extinktion des Lichtes in der Erdatmosphäre. In Handbuch der Astrophysik. Band II, erste Hälfte. Berlin: Springer.

Slingo, A., 1989. A GCM parameterization for the shortwave radiative properties of water clouds. J. Atmos. Sci. 46, 1419–1427. https://doi.org/10.1175/1520-0469(1989)046<1419:AGPFTS>2.0.CO;2

Van Heuklon, T.K., 1979. Estimating atmospheric ozone for solar radiation models. Sol. Energy 22, 63–68. https://doi.org/10.1016/0038-092X(79)90060-4

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