Sea ice at 25km for either hemisphere.
readice_daily(
date,
time.resolution = "daily",
product = "nsidc",
hemisphere = c("south", "north", "both"),
xylim = NULL,
setNA = TRUE,
rescale = FALSE,
latest = TRUE,
returnfiles = FALSE,
...,
inputfiles = NULL,
resample = "bilinear"
)
readice(
date,
time.resolution = "daily",
product = "nsidc",
hemisphere = c("south", "north", "both"),
xylim = NULL,
setNA = TRUE,
rescale = FALSE,
latest = TRUE,
returnfiles = FALSE,
...,
inputfiles = NULL,
resample = "bilinear"
)
readice_monthly(
date,
time.resolution = "monthly",
product = "nsidc",
hemisphere = c("south", "north"),
xylim = NULL,
setNA = TRUE,
rescale = TRUE,
latest = TRUE,
returnfiles = FALSE,
...,
inputfiles = NULL
)date or dates of data to read, see Details
time resoution data to read, daily or monthly
choice of sea ice product, see Details
north or south (or both, if 'both' xylim should be an actual raster or terra grid)
spatial extents to crop from source data, can be anything accepted by extent
mask zero and values greater than 100 as NA
rescale values from integer range?
if TRUE and date input is missing, return the latest time available otherwise the earliest
ignore options and just return the file names and dates
passed to brick, primarily for filename
input the files data base to speed up initialization
warper resampling method used when 'xylim' is a full grid
default for product "amsr" is "hdf" but can be "tif" , extension = "hdf"
raster object
This function relies on the file-listing of icfiles().
Currently available products are
daily or monthly NSIDC concentration data, processed by the SMMR/SSMI NASA Team
Dates are matched to file names by finding the nearest match in
time within a short duration. If date is greater than
length 1 then the sorted set of unique matches is returned.
For NSIDC data a ratifyied raster is returned if setNA and
rescale are both set to FALSE. Use levels(x) to return the data.frame of values
and levels (there's no straight-through rule, all numeric values are explicit along with special
values like "Unused").
The values used are documented here http://nsidc.org/data/docs/daac/nsidc0051_gsfc_seaice.gd.html
If 'both' is specified for hemisphere or if 'xylim' is a full raster grid, the warper is applied to VRT versions of the NSIDC files, which allows them to be combined in one reprojection step. In this case 'xylim' can be specified, to give a projected grid of any form. ' If not supplied (when hemisphere = 'both') then longlat raster at 0.25 degrees is assumed. ('xylim' can be specified as ' a target grid and with only north or south hemisphere applied). When the warper is used, 'setNA' and 'resample' behave the same ' way, though exact results will be different depending on the value of 'resample'.
library(raadtools)
ice <- readice(latest = TRUE)
## can read one or other hemisphere in native projection
readice(hemisphere = "south")
#> class : RasterLayer
#> dimensions : 332, 316, 104912 (nrow, ncol, ncell)
#> resolution : 25000, 25000 (x, y)
#> extent : -3950000, 3950000, -3950000, 4350000 (xmin, xmax, ymin, ymax)
#> crs : +proj=stere +lat_0=-90 +lat_ts=-70 +lon_0=0 +x_0=0 +y_0=0 +a=6378273 +rf=298.279411123061 +units=m +no_defs
#> source : memory
#> names : layer
#> values : 0.4, 100 (min, max)
#> time : 2023-02-01 11:00:00
#>
readice(hemisphere = "north")
#> class : RasterLayer
#> dimensions : 448, 304, 136192 (nrow, ncol, ncell)
#> resolution : 25000, 25000 (x, y)
#> extent : -3850000, 3750000, -5350000, 5850000 (xmin, xmax, ymin, ymax)
#> crs : +proj=stere +lat_0=90 +lat_ts=70 +lon_0=-45 +x_0=0 +y_0=0 +a=6378273 +rf=298.279411123061 +units=m +no_defs
#> source : memory
#> names : layer
#> values : 0.4, 100 (min, max)
#> time : 2023-02-01 11:00:00
#>
## or we can read both, and get longlat by default
readice(hemisphere = "both")
#> for both hemispheres, 'xylim' may be specified - assuming global longlat at 0.25 degree
#> Error in h(simpleError(msg, call)): error in evaluating the argument 'x' in selecting a method for function 'brick': the condition has length > 1
## or set our own grid and read to that
## spex::buffer_extent(extent(c(-.5, .5, -1, 1)* rad * pi), 25000)
tm_ex <- c(-.5, .5, -1, 1) * 20025000
tm_template <- raster(extent(tm_ex), res = 25000, crs = "+proj=tmerc")
readice(hemisphere = "both", xylim = tm_template)
#> Error in h(simpleError(msg, call)): error in evaluating the argument 'x' in selecting a method for function 'brick': the condition has length > 1
## this means we can run extract on global ice, and get 0 in the middle
## extract(readice, data.frame(176, c(-72, 84), as.Date("2020-04-03") + c(0, 100)))
## [1] 80 NA
## extract(readice, data.frame(176, c(-72, 84), as.Date("2020-04-03") + c(0, 100)), hemisphere = "both")
## [1] 78.0 94.4 ## it's interpolated from the original data