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Type:

Package

Title:

Calculation of SSEBI and Evaporative Fraction from Raster Data

Version:

1.0.1

Date:

2025-10-21

Description:

Calculates a modified Simplified Surface Energy Balance Index (SSEBI) and the Evaporative Fraction (EF) using geospatial raster data such as albedo and surface-air temperature difference (TS–TA). The SSEBI is computed from albedo and TS–TA to estimate surface moisture and evaporative dynamics, providing a robust assessment of surface dryness while accounting for atmospheric variations. Based on Roerink, Su, and Menenti (2000) <doi:10.1016/S1464-1909(99)00128-8>.

License:

GPL-3

Encoding:

UTF-8

RoxygenNote:

7.3.2

Imports:

dplyr, stats, terra

Suggests:

testthat (≥ 3.0.0)

NeedsCompilation:

Packaged:

2025-10-28 17:51:10 UTC; hamelin

Author:

Gaelle Hamelin

[aut, cre]

Maintainer:

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

Repository:

CRAN

Date/Publication:

2025-11-03 08:20:02 UTC

Calculate the Evaporative Fraction (EF)

Description

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

Usage

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

Arguments

albedo_path

Character. File path to the albedo 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 albedo values (default: 20).

percentile

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

Details

The input rasters (albedo 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)

albedo_raster <- rast(system.file("extdata", "albedo_reduced.tif", package = "ssebiEF"))
TS_TA_raster <- rast(system.file("extdata", "TS_TA_reduced.tif", package = "ssebiEF"))

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

# Run the function
calculate_EF(
  albedo_path = albedo_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 Simplified Surface Energy Balance Index (SSEBI)