closestdist_gcms: Distance between General Circulation Models (GCMs)

Description

This function compares future climate projections from multiple General Circulation Models (GCMs) based on their similarity in terms of bioclimatic variables. It computes distance metrics between GCMs and identifies subsets of GCMs that are similar to the global set.

Usage

closestdist_gcms(
  s,
  var_names = c("bio_1", "bio_12"),
  study_area = NULL,
  scale = TRUE,
  k = NULL,
  method = "euclidean",
  minimize_difference = TRUE,
  max_difference = NULL
)

Value

A set of GCMs that have a mean distance closer to the global mean distance of all GCMs provided in s.

Arguments

s: A list of stacks of General Circulation Models (GCMs).
var_names: Character. A vector with names of the bioclimatic variables to compare, or 'all' to include all available variables.
study_area: An Extent object, or any object from which an Extent object can be extracted. Defines the study area for cropping and masking the rasters.
scale: Logical. Whether to apply centering and scaling to the data. Default is TRUE.
k: Numeric. The number of GCMs to include in the subset. If NULL (default), stopping criteria are applied.
method: The distance method to use. Default is "euclidean". Possible values are: "euclidean", "maximum", "manhattan", "canberra", "binary", "minkowski", "pearson", "spearman", or "kendall". See ?dist_gcms.
minimize_difference: Logical. If k = NULL, the function will search for the optimal value of k by adding GCMs to the subset until the mean distance starts to diverge from the global mean distance. Default is TRUE.
max_difference: Numeric. A distance threshold to stop searching for the optimal subset. If NULL, no threshold is set. Default is NULL.

Author

Luíz Fernando Esser (luizesser@gmail.com) https://luizfesser.wordpress.com

Details

The minimize_difference option searches for the best value of k by progressively adding GCMs to the subset. The function monitors the mean distance between the subset of GCMs and the global mean distance, stopping when the distance begins to increase. The max_difference option sets a maximum distance difference. If the mean distance between the subset GCMs exceeds this threshold, the function stops searching and returns the current subset.

Examples

Run this code

var_names <- c("bio_1", "bio_12")
s <- import_gcms(system.file("extdata", package = "chooseGCM"), var_names = var_names)
study_area <- terra::ext(c(-80, -30, -50, 10)) |> terra::vect(crs="epsg:4326")
closestdist_gcms(s, var_names, study_area, method = "euclidean")

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