distance_to_ice_edge: Distance to a sea ice 'edge'.

In AustralianAntarcticDivision/raadtools: Tools for Synoptic Environmental Spatial Data

Distance to a sea ice 'edge'.

Description

Calculate the shortest distance (metres) to a threshold sea ice contour. If in doubt use distance_to_ice_edge, the definition of the edge is not straightforward, especially so for the higher resolution products and near the coast. distance_to_ice_edge computes a single "main" edge at continental scale distance_to_ice computes all distances to any ice at threshold concentration

Usage

distance_to_ice_edge(
  date,
  threshold = 15,
  xylim = NULL,
  hemisphere = "south",
  returnfiles = FALSE,
  inputfiles = NULL,
  latest = TRUE,
  ...
)

distance_to_ice(
  date,
  threshold = 15,
  xylim = NULL,
  hemisphere = "south",
  returnfiles = FALSE,
  inputfiles = NULL,
  latest = TRUE,
  ...
)

Arguments

date	date or dates of data to read, see Details
threshold	the sea ice concentration threshold to contour at
xylim	spatial extents to crop from source data, can be anything accepted by extent
hemisphere	"north" or "south", default is "south"
returnfiles	ignore options and just return the file names and dates
inputfiles	input the files data base to speed up initialization
latest	if TRUE and date input is missing, return the latest time available otherwise the earliest
...	passed to brick, primarily for filename

Details

The distance is always positive, use readice in the usual way to determine if a location is inside or out of the ice field itself. (If inside means zero distance to ice for you then set it explicitly based on the concentration a point is in.) Future work may generalize this to other data sources.

Value

raster layer with distances to this date's sea ice edge

Note

beware that any queried location outside of this layer's range will be undetermined, and the external boundary of this layer is not constant with respect to the pole, and that in general a location may be closer to ice in the opposite hemisphere.

The argument hemisphere may be north or south (default is south), but this will only work if your locations are on the actual map, so it's not possible to request the distance to ice in both poles for any point.

Examples

plot(distance_to_ice(latest = TRUE))
plot(distance_to_ice_edge(latest = TRUE))
a = extract(distance_to_ice, aurora[17:25, ])
extract(distance_to_ice, aurora[17:25, ], hemisphere = "south")
# library(trip)
# extract(distance_to_ice_edge, walrus818[seq(50, 400, by = 20), ], hemisphere = "north")

AustralianAntarcticDivision/raadtools documentation built on Nov. 14, 2024, 4:27 p.m.