R/bioclimate.R

In climenv: Download, Extract and Visualise Climate and Elevation Data

#' Holdridge points
#'
#' Calculates the values of bioclimatic indices from monthly temperature and
#' precipitation measurements, following Szelepcsényi et al. 2014.
#'
#' @param temp A matrix or data frame with 12 columns containing
#' temperatures, in degrees C, for each month of the calendar year.
#' @param prec A matrix or data frame with the same dimensions as `temp`,
#' containing precipitation measurements in mm for each month of the year.
#' @returns `bioclimate()` returns a data.frame whose columns
#' correspond to:
#'
#' - `abt`, mean annual biotemperature; mean annual temperature after
#' replacing entries outside the range 0° to 30° with zeros;
#' - `tap`, total annual precipitation (mm);
#' - `per`, potential evapotranspiration ratio
#'
#' @author Martin R. Smith
#' @references
#' Szelepcsényi Z, Breuer H, Sümegi P (2014)
#' The climate of Carpathian Region in the 20th century based on the original
#' and modified Holdridge life zone system.
#' *Cent Eur J Geosci* 6, 293–307. \doi{10.2478/s13533-012-0189-5}
#'
#' Holdridge L. R. (1959) Simple method for determining potential
#' evapotranspiration from temperature data. *Science*, 130, 572.
#' \doi{10.1126/science.130.3375.572}
#' @export
bioclimate <- function(temp, prec) {
  if (!identical(dim(temp), dim(prec))) {
    stop("temp and prec should have the same dimensions")
  }
  if (dim(temp)[2] != 12) {
    stop("Columns of `temp` should correspond to the 12 months")
  }
  biotemp <- temp
  biotemp[temp < 0 | temp > 30] <- 0
  abt <- unname(rowSums(biotemp) / 12)
  tap <- unname(rowSums(prec))
  ape <- abt * 58.93 # Constant given in Holdridge 1959
  per <- ape / tap

  # Return:
  cbind(abt = abt, tap = tap, per = per)
}