R/solar_c.R

In psavoy/StreamLight: An R Package for Estimating Stream Lighting Conditions

#' Calculates solar geometry for use in the SHADE2 model
#' @description Translation of solarC.m
#'
#' @param driver_file The model driver file
#' @param solar_geo Solar geometry, calculated from solar_geo_calc.R
#' @param Lat The site Latitude
#' @param Lon The site Longitude
#'
#' @return Returns solar altitude, azimuth, and declination
#' @export
#===============================================================================
#Calculating solar position and sun-stream geometry
#Created 11/5/2019
#===============================================================================
solar_c <- function(driver_file, solar_geo, Lat, Lon, ...){
  #Calculate the solar altitude, declination, and initial estimate of solar azimuth
    geo_initial <- solar_geo

  #Add a column to store the adjusted azimuth
    geo_initial$solar_azimuth <- NA

  #When Latitude is > solar declination additional considerations are required to
  #determine the correct azimuth
  #Generate a logical index where Latitude is greater than solar declination
    lat_greater <- deg2rad(Lat) > geo_initial[, "solar_dec"]

  #Add a small amount of time (1 minute) and recalculate azimuth
    azimuth_tmp <- azimuth_adj(driver_file = driver_file[lat_greater, ], Lat = Lat, Lon = Lon)

  #Generate a logical index where azimuth_tmp is greater than the initial estimate
    az_tmp_greater <- azimuth_tmp > geo_initial[lat_greater, "solar_azimuth2"]

  #Generate a logical index where both Lat > solar_dec & azimuth_tmp > azimuth
    add_az <- lat_greater == TRUE & az_tmp_greater == TRUE
    geo_initial[add_az, "solar_azimuth"] <- (pi / 2) + geo_initial[add_az, "solar_azimuth2"]


    sub_az <- lat_greater == TRUE & az_tmp_greater == FALSE
    geo_initial[sub_az, "solar_azimuth"] <- (pi / 2) - geo_initial[sub_az, "solar_azimuth2"]

  #When Latitude is < solar declination all angles are 90 - azimuth
    geo_initial[!lat_greater, "solar_azimuth"] <- (pi / 2) - driver_file[!lat_greater, "solar_azimuth2"]

  return(geo_initial[, c("solar_altitude", "solar_azimuth")])

} #End solar_c function