SeaVal (version 1.1.1)

download_chirps_monthly: Download monthly CHIRPS-data

Description

Download CHIRPS monthly data for the GHA-region and save it as netcdfs. The data is downloaded either from the IRI data library or from ICPAC (depending on version), because these data library allows to subset before downloading, unlike the original source at UCSB. As of Feb 2022, the entire CHIRPS-monthly data for the GHA-region is roughly 800MB on disk. The original spatial resolution of CHIRPS is 0.05 degree lon/lat. However, for many applications a coarser resolution is perfectly fine. The function therefore offers the option to also create and save a coarser, upscaled version of the CHIRPS data that allows much faster data processing. Alternatively you can also ONLY save the upscaled version to save disk space (roughly 8MB on disk).

Usage

download_chirps_monthly(
  resolution = "both",
  update = TRUE,
  version = "UCSB",
  years = NULL,
  months = NULL,
  extent = GHA_extent(),
  timeout_limit = 300,
  upscale_grid = data.table(expand.grid(lon = seq(extent[1], extent[2], 0.5), lat =
    seq(extent[3], extent[4], 0.5)))
)

Value

Nothing.

Arguments

resolution

Shall the data be upscaled? Takes one of three arguments:

• 'both' (the default) downloads and saves the data on full resolution and additionally derives an upscaled version. Both will be available later.

• 'high' downloads and saves on original resolution, but does not upscale.

• 'low' (for saving disk space) downloads the original resolution, upscales immediately and only saves the upscaled version.

update

Logical, if TRUE, previously created files are skipped.

version

Should be 'UCSB' (for University of California Santa Barbara, the original source of CHIRPS) or 'ICPAC' (for downloading the ICPAC version CHIRPS blended)

years, months

Which years and months do you want to load? NULL loads everything there is.

extent

vector of length four (xmin,xmax,ymin,ymax), restricting the spatial area.

timeout_limit

how many seconds (per file, i.e. per yearmonth) before the download is aborted?

upscale_grid

The coarse grid to which the data is upscaled (only used when resolution is either 'both' or 'high'). Only change this if you know what you are doing.

Examples

if(interactive()){
download_chirps_monthly(years = 2020, months = 1)
}