Skip to contents

Download and process evapotranspiration data

Source: R/l4h_sebal_modis.R
l4h_sebal_modis.Rd

This function accesses the geeSEBAL-MODIS collection published by the ET-Brasil project, extracts the etp band (daily evapotranspiration in mm/day), and allows temporal aggregation by 8-day images or monthly or yearly composites period. Optionally, results can be returned as sf/tibble objects in R.

[Stable]

Usage

l4h_sebal_modis(
  from,
  to,
  by = "8 days",
  region,
  fun = "mean",
  sf = TRUE,
  force = FALSE,
  quiet = FALSE,
  ...
)

Arguments

from

Start date in "YYYY-MM-DD" format.

to

End date in "YYYY-MM-DD" format.

by

Temporal aggregation frequency. Options: "8 days" (original 8-day composites), "month" (monthly average or sum), or "annual" (annual avergae or sumperiod).

region

A spatial object defining the region of interest. Accepts sf, SpatVector, or ee$FeatureCollection objects.

fun

Aggregation function when by = "month" or "total". Valid values are "mean" or "sum".

sf

Logical. Return result as an sf object? Default is TRUE.

force

Logical. If TRUE, forces download even if a local file already exists.

quiet

Logical. If TRUE, suppress the progress bar (default FALSE).

...

arguments of ee_extract of rgee packages.

Value

A sf or tibble object with etp values.

References

  • Comini,B., Ruhoff,A., Laipelt,L., Fleischmann,A., Huntington,J., Morton,C., Melton,F., Erickson,T., Roberti,D., Souza,V., Biudes,M., Machado,N., Santos,C. & Cosio,E. (2023). geeSEBAL‑MODIS: Continental‑scale evapotranspiration based on the surface energy balance for South America. Preprint. DOI: 10.13140/RG.2.2.17579.11041

  • geeSEBAL‑MODIS v0‑02 dataset. Licensed under the Creative Commons Attribution 4.0 International (CC‑BY‑4.0) license.

Examples

if (FALSE) { # \dontrun{

library(land4health)
ee_Initialize()

# Define a bounding box region in Ucayali, Peru
region <- st_as_sf(st_sfc(
  st_polygon(list(matrix(c(
    -74.1, -4.4,
    -74.1, -3.7,
    -73.2, -3.7,
    -73.2, -4.4,
    -74.1, -4.4
  ), ncol = 2, byrow = TRUE))),
  crs = 4326
))

# 1. Eight-day composites (8 days)
# 2020-01-01 → 2020-12-31, reducer = "mean"
sebal_8d <- l4h_sebal_modis(
  from   = "2020-01-01",
  to     = "2020-12-31",
  region = region
)

# 2. Monthly means
# Same period, but aggregated to calendar months
sebal_month <- l4h_sebal_modis(
  from   = "2020-01-01",
  to     = "2020-12-31",
  by     = "month",
  region = region
)

# 3. Annual evapotranspiration
# 2015 → 2023, one value per year
sebal_annual <- l4h_sebal_modis(
  from   = 2015,
  to     = 2023,
  by     = "annual",
  fun    = "sum",
  region = region,
  sf     = FALSE
)

} # }