readice: Read from NSIDC 25km polar sea ice.

In AustralianAntarcticDivision/raadtools: Tools for Synoptic Environmental Spatial Data

Read from NSIDC 25km polar sea ice.

Description

Sea ice at 25km for either hemisphere.

Usage

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
)

Arguments

date	date or dates of data to read, see Details
time.resolution	time resoution data to read, daily or monthly
product	choice of sea ice product, see Details
hemisphere	north or south (or both, if 'both' xylim should be an actual raster or terra grid)
xylim	spatial extents to crop from source data, can be anything accepted by extent
setNA	mask zero and values greater than 100 as NA
rescale	rescale values from integer range?
latest	if TRUE and date input is missing, return the latest time available otherwise the earliest
returnfiles	ignore options and just return the file names and dates
...	passed to brick, primarily for filename
inputfiles	input the files data base to speed up initialization
resample	warper resampling method used when 'xylim' is a full grid
extension	default for product "amsr" is "hdf" but can be "tif" , extension = "hdf"

Details

This function relies on the file-listing of icfiles().

Currently available products are

'nsidc'

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'.

Value

raster object

See Also

icefiles for details on the repository of data files, raster for the return value

Examples

library(raadtools)
 
ice <- readice(latest = TRUE)

## can read one or other hemisphere in native projection
readice(hemisphere = "south")
readice(hemisphere = "north")
## or we can read both, and get longlat by default
readice(hemisphere = "both")
## 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)

## 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

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