Climatic residence time of a polygon

Function to calculate VoCC-based residence time of isotherms within a polygon after Loaire et al. (2009)

Usage

resTime(pg, vel, areapg = NA)

Arguments

pg: sf object or terra::vect object containing the polygons for which the residence time is to be calculated. The polygons must be on the same coordinate system as vel.
vel: raster with climate velocity (km/year) for the period of interest.
areapg: vector with the area (in km2) of the polygons. Use NA (default) to calculate internally if field not avilable.

Value

a data.frame containing for each polygon its ID, mean velocity (km/yr), diameter of the equivalent circle (km), and residence time (years) as the ratio D/vel.

References

Loarie et al. 2009. The velocity of climate change. Nature, 462, 1052-1055.

Author

Jorge Garcia Molinos

Examples


# Load example Exclusive Economic Zone polygon
if (FALSE) { # \dontrun{
EEZ <- VoCC_get_data("EEZ.gpkg")
HSST <- VoCC_get_data("HSST.tif")

yrSST <- sumSeries(HSST,
  p = "1969-01/2009-12", yr0 = "1955-01-01", l = terra::nlyr(HSST),
  fun = function(x) colMeans(x, na.rm = TRUE),
  freqin = "months", freqout = "years"
)
tr <- tempTrend(yrSST, th = 10)
sg <- spatGrad(yrSST, th = 0.0001, projected = FALSE)
v <- gVoCC(tr, sg)
vel <- v[[1]]

# Calculating area internally
a1 <- resTime(EEZ, vel, areapg = NA)
a1

# Using the area field from the polygon data table
a2 <- resTime(EEZ, vel, areapg = as.numeric(as.numeric(levels(EEZ$Area_km2))[EEZ$Area_km2]))
a2

# Using a user defined polygon
x_coord <- c(-28, -20, -20.3, -25.5)
y_coord <- c(60, 61, 63, 62)
coords <- matrix(c(x_coord, y_coord), ncol = 2)
poly_sf <- sf::st_sf(geometry = sf::st_sfc(sf::st_polygon(list(coords))))
a3 <- resTime(poly_sf, vel, areapg = NA)

terra::plot(vel)
plot(sf::st_geometry(EEZ), add = TRUE)
plot(sf::st_geometry(poly_sf), add = TRUE)
} # }