Download drought index data

The download_drought() function downloads drought index data from publicly available sources. Three source datasets are supported:

SPEI (Standardized Precipitation-Evapotranspiration Index): Multi-year netCDF files by timescale from https://spei.csic.es.
EDDI (Evaporative Demand Drought Index): Weekly raster files by timescale from ftp://ftp.cdc.noaa.gov/Projects/EDDI/CONUS_archive/data.
USDM (U.S. Drought Monitor): Weekly drought class shapefiles from https://droughtmonitor.unl.edu.

Usage

download_drought(
  source = c("spei", "eddi", "usdm"),
  date = c("2020-01-01", "2020-12-31"),
  timescale = 1L,
  directory_to_save = NULL,
  acknowledgement = FALSE,
  hash = FALSE,
  show_progress = TRUE,
  max_tries = 3L,
  rate_limit = 2,
  unzip = TRUE,
  remove_zip = FALSE,
  ...
)

Arguments

source: character(1). Drought data source. One of "spei", "eddi", or "usdm".
date: character(1 or 2). Single date or start/end dates. Format "YYYY-MM-DD". For SPEI/EDDI the year component selects the annual file(s); for USDM the full date is used to select weekly release(s).
timescale: integer(1). Accumulation timescale in months (SPEI/EDDI only; ignored for USDM). Typical values are 1, 3, 6, 12, 24, 48. Default is 1L.
directory_to_save: character(1). Directory to save downloaded data.
acknowledgement: logical(1). Must be TRUE to proceed.
hash: logical(1). Return rlang::hash_file() hash of downloaded files. Default FALSE.
show_progress: logical(1). Show download progress bar. Default TRUE.
max_tries: integer(1). Maximum retry attempts. Default 3L.
rate_limit: numeric(1). Minimum seconds between HTTP requests. Default 2.
unzip: logical(1). Unzip downloaded zip archives (USDM only). Default TRUE.
remove_zip: logical(1). Remove zip archives after unzipping (USDM only). Default FALSE.
...: Reserved for future use; currently ignored.

Value

invisible(NULL) when hash = FALSE; a character hash string when hash = TRUE.

Note

SPEI and EDDI are raster products; USDM is a polygon product (shapefile). Their process_drought() and calculate_drought() handling differ accordingly.
No authentication is required for any of these sources.

Author

Insang Song

Examples

if (FALSE) { # \dontrun{
download_drought(
  source = "spei",
  date = c("2020-01-01", "2020-12-31"),
  timescale = 1L,
  directory_to_save = "./data/drought",
  acknowledgement = TRUE
)
download_drought(
  source = "usdm",
  date = c("2020-01-07", "2020-03-31"),
  directory_to_save = "./data/drought",
  acknowledgement = TRUE
)
} # }