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Download a pre-built wind rose

Source: R/download_wind_rose.R
download_wind_rose.Rd

Downloads a pre-built global wind rose for any combination of years and calendar months, optionally cropped to a region, so that common analyses need no wind data downloads or rose building. Roses are built from hourly 10 m CFSR wind for 1979-2010 with trans = 1; see wind_rose_catalog() for what is available. For other data sets, heights, periods, or trans functions, download wind data with download_wind_data() and build a rose with wind_rose().

Usage

download_wind_rose(
  year = NULL,
  month = NULL,
  ext = NULL,
  source = "cfsr",
  level = "10m",
  cache = is.null(ext),
  quiet = FALSE
)

Arguments

year

Integer vector of years to include. NULL (the default) includes all years.

month

Integer vector of calendar months (1-12) to include in each year. NULL (the default) includes all months. For example, year = 1990:1999, month = 6:8 gives a rose for the summers of the 1990s.

ext

Optional region to crop to: a SpatExtent, an object terra::ext() accepts (e.g. a SpatRaster or SpatVector), or a numeric vector c(xmin, xmax, ymin, ymax), in degrees, with longitudes from -180 to 180. The result includes every cell overlapping ext. Regions crossing the antimeridian are not supported; for those, use the global rose.

source, level

Wind data set and height. Currently only "cfsr" and "10m".

cache

Logical. If TRUE, whole files are downloaded and kept in a cache on disk (see wind_rose_cache()), so later requests for them need no download; each file is about 15 MB. If FALSE, nothing is kept: when ext is given, only the cells within it are read over the internet, which is much faster than downloading whole files for small regions; otherwise files are downloaded to a temporary directory. Defaults to TRUE when ext is NULL and FALSE otherwise.

quiet

Logical. If TRUE, progress messages are suppressed.

Value

A wind_rose, with n_steps and trans recorded so it can be combined with other roses. Values are wind conductance in 1 / hours.

Details

Pre-built roses are stored for single months, calendar years, calendar months across all years, and the full period. A request is met with the fewest of these, combined with combine_roses(), which weights them by their numbers of hours; the result equals the rose built from all of the requested hours at once.

See also

wind_rose_catalog() for the available files; wind_rose_cache() to manage the cache.

Examples

# \donttest{
# long-term rose for the western US, read remotely
rose <- download_wind_rose(ext = c(-125, -100, 30, 50))
#> reading 1 wind rose file remotely

# summers of 1990-1992
summer <- download_wind_rose(year = 1990:1992, month = 6:8, ext = c(-125, -100, 30, 50))
#> reading 9 wind rose files remotely
# }