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Title:

Calculation of the Water Deficit Index (WDI) and the Evaporative Fraction (EF) on Rasters

Version:

1.0.3

Description:

Calculates the Water Deficit Index (WDI) and the Evaporative Fraction (EF) using geospatial data, such as fractional vegetation cover (FVC) and surface-air temperature difference (TS-TA). Terms like "raster", "CRS" are part of standard geospatial terminology.

License:

GPL-3

Encoding:

UTF-8

RoxygenNote:

7.3.2

Imports:

dplyr, stats, terra

Suggests:

testthat (≥ 3.0.0)

Date:

2025-02-19

NeedsCompilation:

Packaged:

2025-02-19 16:38:12 UTC; hamelin

Author:

Gaelle Hamelin

[aut, cre]

Maintainer:

Gaelle Hamelin <gaelle.hamelin@institut-agro.fr>

Repository:

CRAN

Date/Publication:

2025-02-19 17:20:02 UTC

Calculate the Evaporative Fraction (EF)

Description

This function calculates the EF from two rasters: fractional vegetation cover (FVC) and the surface-air temperature difference (TS-TA). It saves the resulting EF raster to the specified output path.

Usage

calculate_EF(
  FVC_path,
  TS_TA_path,
  output_path,
  n_intervals = 20,
  percentile = 0.01
)

Arguments

FVC_path

Character. File path to the FVC raster.Must have the same CRS and extent as the TS-TA raster.

TS_TA_path

Character. File path to the raster of TS-TA (surface-air temperature difference). TS and TA must have the same unit of measurement (Kelvin preferably).

output_path

Character. File path where the EF raster will be saved.

n_intervals

Integer. Number of intervals for splitting FVC values (default: 20).

percentile

Numeric. Percentage used for identifying wet and dry edges (default: 0.01).

Details

The input rasters (FVC and TS-TA) must have the same CRS (Coordinate Reference System) and extent.
If they differ, the function will attempt to reproject and resample the rasters automatically.

Value

A raster object representing the Evaporative Fraction (EF).

Examples

# Paths to example data included in the package
library(terra)

FVC_raster <- rast(system.file("extdata", "FVC_reduced.tif", package = "wdiEF"))
TS_TA_raster <- rast(system.file("extdata", "TS_TA_reduced.tif", package = "wdiEF"))

# Output path (temporary file for example purposes)
output_path <- tempfile(fileext = ".tif")

# Run the function
calculate_EF(
  FVC_path = FVC_raster,
  TS_TA_path = TS_TA_raster,
  output_path = output_path,
  n_intervals = 20,
  percentile = 0.01
)

# Print the output path
print(output_path)

Calculate the Water Deficit Index (WDI)