gridboxmean {cmsafops}

Determine means of selected grid boxes

Description

The function determines means of selected grid boxes from data of a single CM SAF NetCDF input file.

Usage

gridboxmean(
  var,
  lonGrid,
  latGrid,
  infile,
  outfile,
  nc34 = 4,
  overwrite = FALSE,
  verbose = FALSE,
  nc = NULL
)

Arguments

var

Name of NetCDF variable (character).

lonGrid

INTEGER Number of grid boxes in x direction

latGrid

INTEGER Number of grid boxes in y direction

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 means of selected grid boxes is written.

See Also

Other grid boxes statistics: gridboxmax(), gridboxmin(), gridboxrange(), gridboxsd(), gridboxsum(), gridboxvar()

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("2000-03-01"), as.Date("2000-05-31"), "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, 3))

## 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_1 <- nc_create(file.path(tempdir(), "CMSAF_example_file.nc"), vars)

ncvar_put(ncnew_1, var1, data)

ncatt_put(ncnew_1, "lon", "standard_name", "longitude", prec = "text")
ncatt_put(ncnew_1, "lat", "standard_name", "latitude", prec = "text")
nc_close(ncnew_1)

## Determine the means of selected grid boxes of the example CM SAF NetCDF file 
## and write the output to a new file.
gridboxmean(var = "SIS", lonGrid = 4, latGrid = 4, infile = file.path(tempdir(), 
 "CMSAF_example_file.nc"), outfile = file.path(tempdir(), 
 "CMSAF_example_file_gridboxmean.nc"))

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