R/radiation_parameters.R

In BrazilMet: Download and Processing of Automatic Weather Stations (AWS) Data of INMET-Brazil

#' Extraterrestrial radiation for daily periods (ra)
#' @description ra is expressed in MJ m-2 day-1
#' @param latitude A dataframe with latitude in decimal degrees that you want to calculate the ra.
#' @param date A dataframe with the dates that you want to calculate the ra.
#' @examples
#' \dontrun{
#' ra <- ra_calculation(latitude, date)
#' }
#' @export
#' @return A data.frame with the extraterrestrial radiation for daily periods
#' @author Roberto Filgueiras, Luan P. Venancio, Catariny C. Aleman and Fernando F. da Cunha


ra_calculation <- function(latitude, date) {
  julian_day <- as.data.frame(as.numeric(format(date, "%j")))
  lat_rad <- (pi / 180) * (latitude)
  dr <- 1 + 0.033 * cos((2 * pi / 365) * julian_day)
  solar_declination <- 0.409 * sin(((2 * pi / 365) * julian_day) - 1.39)
  sunset_hour_angle <- acos(-tan(lat_rad) * tan(solar_declination))
  ra <- ((24 * (60)) / pi) * (0.0820) * dr * (sunset_hour_angle * sin(lat_rad) * sin(solar_declination) + cos(lat_rad) * cos(solar_declination) * sin(sunset_hour_angle))
  ra <- as.data.frame(ra)
  colnames(ra) <- "ra"
  return(ra)
}


#' Solar radiation based in Angstrom formula (sr_ang)
#' @description If global radiation is not measure at station, it can be estimated with this function.
#' @param latitude A dataframe with latitude in decimal degrees that you want to calculate the ra.
#' @param date A dataframe with the dates that you want to calculate the ra.
#' @param n The actual duration of sunshine. This variable is recorded with Campbell-Stokes sunshine recorder.
#' @param as A dataframe with latitude in decimal degrees that you want to calculate the ra. The values of as = 0.25 is recommended by Allen et al. (1998).
#' @param bs A dataframe with the dates that you want to calculate the ra. The values of bs = 0.50 is recommended by Allen et al. (1998).
#' @examples
#' \dontrun{
#' sr_ang <- sr_ang_calculation(latitude, date, n, as, bs)
#' }
#' @export
#' @return A data.frame object with solar radiation data
#' @author Roberto Filgueiras, Luan P. Venancio, Catariny C. Aleman and Fernando F. da Cunha

sr_ang_calculation <- function(latitude, date, n, as, bs) {
  julian_day <- as.data.frame(as.numeric(format(date, "%j")))
  lat_rad <- (pi / 180) * (latitude)
  dr <- 1 + 0.033 * cos((2 * pi / 365) * julian_day)
  solar_declination <- 0.409 * sin(((2 * pi / 365) * julian_day) - 1.39)
  sunset_hour_angle <- acos(-tan(lat_rad) * tan(solar_declination))
  ra <- ((24 * (60)) / pi) * (0.0820) * dr * (sunset_hour_angle * sin(lat_rad) * sin(solar_declination) + cos(lat_rad) * cos(solar_declination) * sin(sunset_hour_angle))
  ra <- as.data.frame(ra)
  N <- (24 / pi) * sunset_hour_angle
  sr_ang <- (as + bs * (n / N)) * ra
  sr_ang <- as.data.frame(sr_ang)
  colnames(sr_ang) <- "sr_ang"
  return(sr_ang)
}

#' Solar radiation data derived from air temperature differences
#' @description If global radiation is not measure at station, it can be estimated with this function.
#' @param latitude A dataframe with latitude in decimal degrees that you want to calculate the ra.
#' @param date A dataframe with the dates that you want to calculate the ra.
#' @param location_krs Adjustment coefficient based in location. Please decide between "coastal or "interior". If coastal the krs will be 0.19, if interior the krs will be 0.16.
#' @param tmin A dataframe with Minimum daily air temperature (°C)
#' @param tmax A dataframe with Maximum daily air temperature (°C)
#' @examples
#' \dontrun{
#' sr_tair <- sr_tair_calculation(latitude, date, tmax, tmin, location_krs)
#' }
#' @export
#' @return A data.frame object with solar radiation data
#' @author Roberto Filgueiras, Luan P. Venancio, Catariny C. Aleman and Fernando F. da Cunha

sr_tair_calculation <- function(latitude, date, tmax, tmin, location_krs) {
  if (location_krs == "interior") {
    krs <- 0.16
  } else {
    if (location_krs == "coastal") {
      krs <- 0.19
    } else {
      krs <- NULL
    }
  }


  julian_day <- as.data.frame(as.numeric(format(date, "%j")))
  lat_rad <- (pi / 180) * (latitude)
  dr <- 1 + 0.033 * cos((2 * pi / 365) * julian_day)
  solar_declination <- 0.409 * sin(((2 * pi / 365) * julian_day) - 1.39)
  sunset_hour_angle <- acos(-tan(lat_rad) * tan(solar_declination))
  ra <- ((24 * (60)) / pi) * (0.0820) * dr * (sunset_hour_angle * sin(lat_rad) * sin(solar_declination) + cos(lat_rad) * cos(solar_declination) * sin(sunset_hour_angle))
  ra <- as.data.frame(ra)
  sr_tair <- krs * sqrt(tmax - tmin) * ra
  sr_tair <- as.data.frame(sr_tair)
  colnames(sr_tair) <- "sr_tair"
  return(sr_tair)
}

#' Clear-sky solar radiation with calibrated values available
#' @description Clear-sky solar radiation is calculated in this function for near sea level or when calibrated values for as and bs are available.
#' @param as A dataframe with latitude in decimal degrees that you want to calculate the ra. The values of as = 0.25 is recommended by Allen et al. (1998).
#' @param bs A dataframe with the dates that you want to calculate the ra. The values of bs = 0.50 is recommended by Allen et al. (1998).
#' @param ra Extraterrestrial radiation for daily periods (ra).
#' @examples
#' \dontrun{
#' rso_df <- rso_calculation_1(as, bs, ra)
#' }
#' @export
#' @return A data.frame object with the clear-sky radiation data
#' @author Roberto Filgueiras, Luan P. Venancio, Catariny C. Aleman and Fernando F. da Cunha

rso_calculation_1 <- function(as, bs, ra) {
  rso1 <- (as + bs) * ra
  rso1 <- as.data.frame(rso1)
  colnames(rso1) <- "rso1"
  return(rso1)
}


#' Solar radiation data from a nearby weather station
#' @description The solar radiation data is calculated based in a nearby weather station.
#' @param rs_reg A dataframe with the solar radiation at the regional location (MJ m-2 day-1).
#' @param ra_reg A dataframe with the extraterrestrial radiation at the regional location (MJ m-2 day-1).
#' @param ra A dataframe with the extraterrestrial radiation for daily periods (ra).
#' @examples
#' \dontrun{
#' rs_nearby_df <- rs_nearby_calculation(rs_reg, ra_reg, ra)
#' }
#' @export
#' @return A data.frame object with the Solar radiation data based on a nearby weather station
#' @author Roberto Filgueiras, Luan P. Venancio, Catariny C. Aleman and Fernando F. da Cunha

rs_nearby_calculation <- function(rs_reg, ra_reg, ra) {
  rs_nearby <- (rs_reg / ra_reg) * ra
  rs_nearby <- as.data.frame(rs_nearby)
  colnames(rs_nearby) <- "rs_nearby"
  return(rs_nearby)
}

#' Clear-sky solar radiation when calibrated values are not available
#' @description Clear-sky solar radiation is calculated in this function for near sea level or when calibrated values for as and bs are available.
#' @param z Station elevation above sea level (m)
#' @param ra Extraterrestrial radiation for daily periods (ra).
#' @examples
#' \dontrun{
#' rso_df <- rso_calculation_2(z, ra)
#' }
#' @export
#' @return A data.frame object with the clear-sky solar radiation
#' @author Roberto Filgueiras, Luan P. Venancio, Catariny C. Aleman and Fernando F. da Cunha

rso_calculation_2 <- function(z, ra) {
  rso2 <- (0.75 + 0.00002 * z) * ra
  rso2 <- as.data.frame(rso2)
  colnames(rso2) <- "rso2"
  return(rso2)
}

#' Net solar or net shortwave radiation (rns)
#' @description The rns results form the balance between incoming and reflected solar radiation (MJ m-2 day-1).
#' @param albedo Albedo or canopy reflectance coefficient. The 0.23 is the value used for hypothetical grass reference crop (dimensionless).
#' @param rs The incoming solar radiation (MJ m-2 day-1).
#' @examples
#' \dontrun{
#' ra <- rns_calculation(albedo, rs)
#' }
#' @export
#' @return A data.frame object with the net solar or net shortwave radiation data.
#' @author Roberto Filgueiras, Luan P. Venancio, Catariny C. Aleman and Fernando F. da Cunha


rns_calculation <- function(albedo, rs) {
  rns <- (1 - albedo) * rs
  rns <- as.data.frame(rns)
  colnames(rns) <- "rns"
  return(rns)
}

#' Net longwave radiation (rnl)
#' @description Net outgoing longwave radiation is calculate with this function
#' @param tmin A dataframe with Minimum daily air temperature (°C)
#' @param tmax A dataframe with Maximum daily air temperature (°C)
#' @param ea A dataframe with the actual vapour pressure (KPa).
#' @param rs A dataframe with the incomimg solar radiation (MJ m-2 day-1).
#' @param rso A dataframe with the clear-sky radiation (MJ m-2 day-1)
#' @examples
#' \dontrun{
#' rnl_df <- rnl_calculation(tmin, tmax, ea, rs, rso)
#' }
#' @export
#' @return A data.frame object with the net longwave radiation.
#' @author Roberto Filgueiras, Luan P. Venancio, Catariny C. Aleman and Fernando F. da Cunha


rnl_calculation <- function(tmin, tmax, ea, rs, rso) {
  sb_constant <- 0.000000004903
  rs_rso <- rs / rso
  if (rs_rso > 1) {
    rs_rso <- 1
  } else {
    rs_rso
  }
  rnl <- sb_constant * ((((tmax + 273.15)^4) + ((tmin + 273.15)^4)) / 2) * (0.34 - (0.14 * sqrt(ea))) * ((1.35 * (rs_rso)) - 0.35)
  rnl <- as.data.frame(rnl)
  colnames(rnl) <- "rnl"
  return(rnl)
}

#' Net radiation (rn)
#' @description  The net radiation (MJ m-2 day-1) is the difference between the incoming net shortwave radiation (rns) and the outgoing net longwave radiation (rnl).
#' @param rns The incomimg net shortwave radiation (MJ m-2 day-1).
#' @param rnl The outgoing net longwave radiation (MJ m-2 day-1).
#' @examples
#' \dontrun{
#' rn <- rn_calculation(rns, rnl)
#' }
#' @export
#' @return A data.frame object with the net radiation data.
#' @author Roberto Filgueiras, Luan P. Venancio, Catariny C. Aleman and Fernando F. da Cunha


rn_calculation <- function(rns, rnl) {
  rn <- (rns - rnl)
  rn <- as.data.frame(rn)
  colnames(rn) <- "rn"
  return(rn)
}