R: Download and Cache an amsr File

download.amsr {oce} | R Documentation

## Download and Cache an amsr File

### Description

If the file is already present in `destdir`, then it is not downloaded again. The default `destdir` is the present directory, but it probably makes more sense to use something like `"~/data/amsr"` to make it easy for scripts in other directories to use the cached data. The file is downloaded with `download.file()`.

### Usage

    download.amsr(
      year,
      month,
      day,
      destdir = ".",
      server = "http://data.remss.com/amsr2/bmaps_v08"
    )

### Arguments

`year, month, day` | Numerical values of the year, month, and day of the desired dataset. Note that one file is archived per day, so these three values uniquely identify a dataset. If `day` and `month` are not provided but `day` is, then the time is provided in a relative sense, based on the present date, with `day` indicating the number of days in the past. Owing to issues with timezones and the time when the data are uploaded to the server, `day=3` may yield the most recent available data. For this reason, there is a third option, which is to leave `day` unspecified, which works as though `day=3` had been given.
`destdir` | A string naming the directory in which to cache the downloaded file. The default is to store in the present directory, but many users find it more helpful to use something like `"~/data/amsr"` for this, to collect all downloaded amsr files in one place.
`server` | A string naming the server from which data are to be acquired. See “History”.

### Value

A character value indicating the filename of the result; if there is a problem of any kind, the result will be the empty string.

### History

Until 25 March 2017, the default server was `"ftp.ssmi.com/amsr2/bmaps_v07.2"`, but this was changed when the author discovered that this FTP site had been changed to require users to create accounts to register for downloads. The default was changed to `"http://data.remss.com/amsr2/bmaps_v07.2"` on the named date. This site was found by a web search, but it seems to provide proper data. It is assumed that users will do some checking on the best source.

On 23 January 2018, it was noticed that the server-url naming convention had changed, e.g. `http://data.remss.com/amsr2/bmaps_v07.2/y2017/m01/f34_20170114v7.2.gz` becoming `http://data.remss.com/amsr2/bmaps_v08/y2017/m01/f34_20170114v8.gz`

### References

`http://images.remss.com/amsr/amsr2_data_daily.html` provides daily images going back to 2012. Three-day, monthly, and monthly composites are also provided on that site.

### See Also

Other functions that download files: `download.coastline()`, `download.met()`, `download.topo()`

Other things related to amsr data: `[[,amsr-method`, `[[<-,amsr-method`, `amsr-class`, `composite,amsr-method`, `plot,amsr-method`, `read.amsr()`, `subset,amsr-method`, `summary,amsr-method`

### Examples

    ## Not run:
    ## The download takes several seconds.
    f <- download.amsr(2017, 1, 14) # Jan 14, 2017
    d <- read.amsr(f)
    plot(d)
    mtext(d[["filename"]], side=3, line=0, adj=0)

    ## End(Not run)

[Package oce version 1.2-0 Index]