Calculate Aridity Index

日本語版はこちら (Japanese version)

This chapter calculates the Aridity Index (AI), a dryness indicator defined as the ratio of precipitation to potential evapotranspiration (World Atlas of Desertification 1992).

\[AI = \frac{P}{PET}\]

where \(P\) is precipitation and \(PET\) is potential evapotranspiration.

Load libraries

Load data

data_dir <- Sys.getenv("PROJECT_DATA_DIR")
sf_climate <- readRDS(file.path(
  data_dir,
  "climate_mesh_data_joined/climate_mesh_data_with_pet.rds"
))

Calculate Aridity Index

sf_climate$aridity_index <- sf_climate$precipitation_year / sf_climate$PET_year

Save data

saveRDS(
  sf_climate,
  file.path(
    data_dir,
    "climate_mesh_data_joined/climate_mesh_data_with_aridity_index.rds"
  )
)
df_climate <- st_drop_geometry(sf_climate)
write.csv(
  df_climate,
  file.path(
    data_dir,
    "climate_mesh_data_joined/climate_mesh_data_with_aridity_index.csv"
  ),
  row.names = FALSE
)

References

World Atlas of Desertification. 1992. UNEP.