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