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This functions allows to calculate precipitation statistics based on the CHIRPS rainfall estimates. Corresponding to the time-frame of the analysis of the portfolio, monthly precipitation statistics are calculated. These include the total rainfall amount, rainfall anomaly against the 1981-2010 climate normal, and the Standardized Precipitation Index (SPI) which is available for scales between 1 and 48 months. Th function needs the SPEI package to be installed. The required resources for this indicator are:

Format

A tibble with a column for years, months, absolute rainfall (in mm), rainfall anomaly (in mm) and one or more columns per selected time-scale for SPI (dimensionless).

Details

The following arguments can be set:

scales_spi

An integer vector indicating the scales for which to calculate the SPI.

spi_previous_year

An integer specifying how many previous years to include in order to fit the SPI. Defaults to 8 years.

engine

The preferred processing functions from either one of "zonal", "extract" or "exactextract" as character.

Examples

# \dontshow{
mapme.biodiversity:::.copy_resource_dir(file.path(tempdir(), "mapme-data"))
# }
# \dontrun{
library(sf)
library(mapme.biodiversity)

outdir <- file.path(tempdir(), "mapme-data")
dir.create(outdir, showWarnings = FALSE)

aoi <- system.file("extdata", "sierra_de_neiba_478140_2.gpkg",
  package = "mapme.biodiversity"
) %>%
  read_sf() %>%
  init_portfolio(
    years = 2010,
    outdir = outdir,
    tmpdir = tempdir(),
    verbose = FALSE
  ) %>%
  get_resources("chirps") %>%
  calc_indicators("precipitation_chirps",
    engine = "exactextract",
    scales_spi = 3,
    spi_prev_years = 8
  ) %>%
  tidyr::unnest(precipitation_chirps)
#> Error in map2(.x, vec_index(.x), .f, ...):  In index: 1.
#>  With name: chirps.
#> Caused by error in `reader()`:
#> ! Did not find equal number of tiles per timestep.

aoi
#> Error in eval(expr, envir, enclos): object 'aoi' not found
# }