extract_smos {smosr}

Extract BEC-SMOS soil moisture estimates for specific geographical locations

Description

This function facilitates reading of the original BEC-SMOS soil moisture data files and extracting relevant information for specific geographical locations by using Lat/Lon coordinates in decimal degrees.

Usage

extract_smos(
  data,
  lat,
  lon,
  save = FALSE,
  dir = NULL,
  filename = "smosr_output.csv"
)

Arguments

data

a character vector as produced by list_smos() containing links to the data files on the local computer.

lat

a numeric vector containing latitudes of geographical locations to extract the data from (in ‘latlon’ projection).

lon

a numeric vector containing longitudes of geographical locations to extract the data from (in ‘latlon’ projection).

save

a logical vector indicating whether the output should be saved as a CSV file. Default is FALSE.

dir

a character string specifying a path to a local directory in which to save the CSV file with the output. Default value is NULL meaning that the file is stored in a temporary directory of the current R session.

filename

a character string naming the CSV file for saving the output. If save = TRUE and no filename is specified by the user, the data is saved in a file with a generic name ‘smosr_output.csv’.

Details

This function reads the original BEC-SMOS soil moisture data files in NetCDF format, converts data from EASE-2 grid cells to geographic coordinates, and extracts relevant information for Lat/Lon locations specified by the user.

The data retrieved from each data file includes:

- the coordinates of spatial points (Lon and Lat) from which the data were extracted;

- frequency and SMOS orbit of each file over which the function iterated;

- date and time when the data was obtained;

- soil moisture estimate (SM);

- quality assurance (QA) flag corresponding to each SM estimate.

The output of this function could be saved as a CSV file.

Value

a data.matrix with the relevant information as described in Details.

References

Pablos M, Gonzalez-Haro C, Portal G, Piles M, Vall-llossera M, Portabella M (2022). SMOS L4 Surface Soil Moisture downscaled maps at 1 km EASE-2 (reprocessed mode) (V.6.0) [Dataset].

Examples

## Not run: 
# to iterate over a list of BEC-SMOS data files produced by list_smos() and
# extract soil moisture estimates for the specified geographical locations
smos_files <- list_smos()
lat <- c(40.42, 41.90, 48.86, 52.50, 59.91)
lon <- c(-3.70, 12.50, 2.35, 13.40, 10.75)
sm_estimates <- extract_smos(data = smos_files, lat = lat, lon = lon)

## End(Not run)