seassd: Determine seasonal standard deviations

In cmsafops: Tools for CM SAF NetCDF Data

Determine seasonal standard deviations

Description

The function determines seasonal standard deviations values from data of a single CM SAF NetCDF input file. The seasonal standard deviations is only determined if all three months of a season are available. For (north-) winter this are January, February and the December of the previous year (DJF). The other seasons are MAM, JJA, and SON.

Usage

seassd(
  var,
  infile,
  outfile,
  nc34 = 4,
  overwrite = FALSE,
  verbose = FALSE,
  nc = NULL
)

Arguments

var	Name of NetCDF variable (character).
infile	Filename of input NetCDF file. This may include the directory (character).
outfile	Filename of output NetCDF file. This may include the directory (character).
nc34	NetCDF version of output file. If nc34 = 3 the output file will be in NetCDFv3 format (numeric). Default output is NetCDFv4.
overwrite	logical; should existing output file be overwritten?
verbose	logical; if TRUE, progress messages are shown
nc	Alternatively to infile you can specify the input as an object of class ncdf4 (as returned from ncdf4::nc_open).

Value

A NetCDF file including a time series of seasonal standard deviations is written.

See Also

Other seasonal statistics: seas.anomaly(), seasmean(), seassum(), seasvar(), yseasmax(), yseasmean(), yseasmin(), yseassd()

Examples

## Create an example NetCDF file with a similar structure as used by CM
## SAF. The file is created with the ncdf4 package.  Alternatively
## example data can be freely downloaded here: <https://wui.cmsaf.eu/>

library(ncdf4)

## create some (non-realistic) example data

lon <- seq(5, 15, 0.5)
lat <- seq(45, 55, 0.5)
time <- seq(as.Date("2000-01-01"), as.Date("2010-12-31"), "month")
origin <- as.Date("1983-01-01 00:00:00")
time <- as.numeric(difftime(time, origin, units = "hour"))
data <- array(250:350, dim = c(21, 21, 132))

## create example NetCDF

x <- ncdim_def(name = "lon", units = "degrees_east", vals = lon)
y <- ncdim_def(name = "lat", units = "degrees_north", vals = lat)
t <- ncdim_def(name = "time", units = "hours since 1983-01-01 00:00:00",
 vals = time, unlim = TRUE)
var1 <- ncvar_def("SIS", "W m-2", list(x, y, t), -1, prec = "short")
vars <- list(var1)
ncnew <- nc_create(file.path(tempdir(),"CMSAF_example_file.nc"), vars)
ncvar_put(ncnew, var1, data)
ncatt_put(ncnew, "lon", "standard_name", "longitude", prec = "text")
ncatt_put(ncnew, "lat", "standard_name", "latitude", prec = "text")
nc_close(ncnew)

## Determine the seasonal standard deviations of the example CM SAF NetCDF file and
## write the output to a new file.
seassd(var = "SIS", infile = file.path(tempdir(),"CMSAF_example_file.nc"), 
 outfile = file.path(tempdir(),"CMSAF_example_file_seassd.nc"))

unlink(c(file.path(tempdir(),"CMSAF_example_file.nc"), 
 file.path(tempdir(),"CMSAF_example_file_seassd.nc")))

cmsafops documentation built on Sept. 18, 2023, 5:16 p.m.