ag5_extract function

Extract AgERA5 data stored in a local hard drive

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.

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

Returns

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"
• "liquid_precipitation_duration_fraction"
• "snow_thickness_lwe"
• "Solar-Radiation-Flux"
• "Temperature-Air-2m"
• "2m_dewpoint_temperature"
• "Precipitation-Flux"
• "solid_precipitation_duration_fraction"
• "snow_thickness"
• "vapour_pressure"
• "10m_wind_speed"
• "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.

• cloud_cover
• snow_thickness_lwe
• 2m_dewpoint_temperature
• snow_thickness
• vapour_pressure
• 10m_wind_speed

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

• 06h
• 09h
• 12h
• 15h
• 18h

Examples

## Not run:

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/")
## End(Not run)

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