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Extract AgERA5 data stored in a local hard drive

ag5_extract.Rd

Extract data from AgERA5 data files previously downloaded from the Copernicus Climate Data Store. These functions use package 'terra' to read *.nc files and extract the requested data for a given location and dates. If dates is one value it extracts a single observation for the specified variable and location. If dates is a character vector of length == 2, it will extract a time series of the specified variable and location, where the first dates value is the start date and the second the end date.

Usage

ag5_extract(coords, ..., path)

# S3 method for class 'numeric'
ag5_extract(
  coords,
  dates,
  variable,
  statistic = NULL,
  time = NULL,
  celsius = FALSE,
  parallel = TRUE,
  ...,
  path
)

# S3 method for class 'data.frame'
ag5_extract(
  coords,
  lon = "lon",
  lat = "lat",
  start_date = "start_date",
  end_date = "end_date",
  variable,
  statistic = NULL,
  time = NULL,
  celsius = FALSE,
  ncores = NULL,
  ...,
  path
)

Arguments

coords

numeric vector of length = 2 of the form (lon, lat), or a data.frame with required columns

...

Other parameters

path

character The path for the folder containing the AgERA5 files

dates

character The dates for extracting the specified variable, a vector of length 1 extracts a single date, while a vector of length 2 indicates the start and end dates. or the column name in the case of data.frame

variable

character The AgERA5 variable to extract, see details for available options

statistic

character Only for some variables, see details for valid options

time

Only for variable Relative-Humidity-2m, see details for valid options

celsius

logical Only for variables "Temperature-Air-2m" and "2m_dewpoint_temperature".

parallel

logical Use parallel computation to speed-up data processing

lon

character Column name of longitude values in the case of data.frame

lat

character Column name of latitude values in the case of data.frame

start_date

character Column name of start_date values in the case that coords is a data.frame

end_date

character Column name of end_date values in the case that coords is a data.frame

ncores

Number of cores to use with parallel. If NULL and parallel is ON, half the available cores will be used. If TRUE the values are converted from Kelvin to Celsius. Default is FALSE

Value

numeric vector with length equal to the number of dates between first and second date. The returned vecter is a named vector, with requested dates as names. If only one date is provided the function returns a numeric vector with length = 1. If coords is a data.frame, the function returns a list of numeric vectors, each one corresponding to the rows in the input data.frame

Valid variable values

  • "Cloud-Cover"

  • "Precipitation-Rain-Duration-Fraction"

  • "Snow-Thickness-LWE"

  • "Solar-Radiation-Flux"

  • "Temperature-Air-2m"

  • "Dew-Point_Temperature-2m"

  • "Precipitation-Flux"

  • "Precipitation-Solid-Duration-Fraction"

  • "Snow-Thickness"

  • "Vapour-Pressure"

  • "Wind-Speed-10m"

  • "Relative-Humidity-2m"

Valid statistics for variable "Temperature-Air-2m"

  • "Max-24h"

  • "Mean-24h"

  • "Min-24h"

  • "Max-Day-Time"

  • "Mean-Day-Time"

  • "Mean-Night-Time"

  • "Min-Night-Time"

Variables that require statistic

For the following variables, only 24 hour mean statistic is available, but should be explicitly indicated as "Mean".

  • "Cloud-Cover"

  • "Snow-Thickness-LWE"

  • "Dew-Point_Temperature-2m"

  • "Snow-Thickness"

  • "Vapour-Pressure"

  • "Wind-Speed-10m"

Valid time values for variable "Relative-Humidity-2m"

  • "06h"

  • "09h"

  • "12h"

  • "15h"

  • "18h"

References

Temperature conversion is made accordingly to: Preston-Thomas, H. (1990). The International Temperature Scale of 1990 (ITS-90). Metrologia, 27(1), 3-10. doi:10.1088/0026-1394/27/1/002

Examples

if (FALSE) { # \dontrun{
temp <- ag5_extract(coords = c(lon = 35.72636, lat = -2.197162),
                      dates = "1991-04-22",
                      variable = "Temperature-Air-2m",
                      statistic = "Max-Day-Time",
                      path = "C:/temperature_data/")
} # }