R/surface_fuel_consumption.r

In nrcan-cfs-fire/cffdrs: Canadian Forest Fire Danger Rating System

#' Surface Fuel Consumption Calculator
#'
#'   @description Computes the Surface Fuel Consumption by Fuel Type.
#'   All variables names are laid out in the same manner as FCFDG (1992) or
#'   Wotton et. al (2009)
#'
#'   Forestry Canada Fire Danger Group (FCFDG) (1992). "Development and
#'   Structure of the Canadian Forest Fire Behavior Prediction System."
#'   Technical Report ST-X-3, Forestry Canada, Ottawa, Ontario.
#'
#'   Wotton, B.M., Alexander, M.E., Taylor, S.W. 2009. Updates and revisions to
#'   the 1992 Canadian forest fire behavior prediction system. Nat. Resour.
#'   Can., Can. For. Serv., Great Lakes For. Cent., Sault Ste. Marie, Ontario,
#'   Canada. Information Report GLC-X-10, 45p.
#'
#' @param FUELTYPE The Fire Behaviour Prediction FuelType
#' @param BUI      Buildup Index
#' @param FFMC     Fine Fuel Moisture Code
#' @param PC       Percent Conifer (%)
#' @param GFL      Grass Fuel Load (kg/m^2)
#'
#' @returns   SFC Surface Fuel Consumption (kg/m^2)
#'
#' @noRd

surface_fuel_consumption <- function(FUELTYPE, FFMC, BUI, PC, GFL) {
  SFC <- rep(-999, length(FFMC))
  # Eqs. 9a, 9b (Wotton et. al. 2009) - Solving the lower bound of FFMC value
  # for the C1 fuel type SFC calculation
  SFC <- ifelse(
    FUELTYPE == "C1",
    ifelse(
      FFMC > 84,
      0.75 + 0.75 * (1 - exp(-0.23 * (FFMC - 84)))**0.5,
      0.75 - 0.75 * (1 - exp(-0.23 * (84 - FFMC)))**0.5
    ),
    SFC
  )
  # Eq. 10 (FCFDG 1992) - C2, M3, and M4 Fuel Types
  SFC <- ifelse(
    FUELTYPE == "C2" | FUELTYPE == "M3" | FUELTYPE == "M4",
    5.0 * (1 - exp(-0.0115 * BUI)),
    SFC
  )
  # Eq. 11 (FCFDG 1992) - C3, C4 Fuel Types
  SFC <- ifelse(
    FUELTYPE == "C3" | FUELTYPE == "C4",
    5.0 * (1 - exp(-0.0164 * BUI))**2.24,
    SFC
  )
  # Eq. 12 (FCFDG 1992) - C5, C6 Fuel Types
  SFC <- ifelse(
    FUELTYPE == "C5" | FUELTYPE == "C6",
    5.0 * (1 - exp(-0.0149 * BUI))**2.48,
    SFC
  )
  # Eqs. 13, 14, 15 (FCFDG 1992) - C7 Fuel Types
  SFC <- ifelse(
    FUELTYPE == "C7",
    ifelse(
      FFMC > 70,
      2 * (1 - exp(-0.104 * (FFMC - 70))),
      0
    ) + 1.5 * (1 - exp(-0.0201 * BUI)),
    SFC
  )
  # Eq. 16 (FCFDG 1992) - D1 Fuel Type
  SFC <- ifelse(FUELTYPE == "D1", 1.5 * (1 - exp(-0.0183 * BUI)), SFC)
  # Eq. 17 (FCFDG 1992) - M1 and M2 Fuel Types
  SFC <- ifelse(
    FUELTYPE == "M1" | FUELTYPE == "M2",
    (PC / 100 * (5.0 * (1 - exp(-0.0115 * BUI)))
      + ((100 - PC) / 100 * (1.5 * (1 - exp(-0.0183 * BUI))))),
    SFC
  )
  # Eq. 18 (FCFDG 1992) - Grass Fuel Types
  SFC <- ifelse(FUELTYPE == "O1A" | FUELTYPE == "O1B", GFL, SFC)
  # Eq. 19, 20, 25 (FCFDG 1992) - S1 Fuel Type
  SFC <- ifelse(
    FUELTYPE == "S1",
    4.0 * (1 - exp(-0.025 * BUI)) + 4.0 * (1 - exp(-0.034 * BUI)),
    SFC
  )
  # Eq. 21, 22, 25 (FCFDG 1992) - S2 Fuel Type
  SFC <- ifelse(
    FUELTYPE == "S2",
    10.0 * (1 - exp(-0.013 * BUI)) + 6.0 * (1 - exp(-0.060 * BUI)),
    SFC
  )
  # Eq. 23, 24, 25 (FCFDG 1992) - S3 Fuel Type
  SFC <- ifelse(
    FUELTYPE == "S3",
    12.0 * (1 - exp(-0.0166 * BUI)) + 20.0 * (1 - exp(-0.0210 * BUI)),
    SFC
  )
  # Constrain SFC value
  SFC <- ifelse(SFC <= 0, 0.000001, SFC)
  return(SFC)
}

.SFCcalc <- function(...) {
  .Deprecated("surface_fuel_consumption")
  return(surface_fuel_consumption(...))
}