eddi: R package for the NOAA Evaporative Demand Drought Index

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The eddi R package facilitates access to the NOAA Evaporative Demand Drought Index (EDDI) data product.


You can install the development version of eddi with devtools:

# install.packages("devtools")


The EDDI product exists for multiple timescales, including the 1 to 12 week and 1 to 12 months scales. Shorter time scales can detect short term droughts, e.g., “flash droughts”, and longer time scales are appropriate for detecting long term drought. For more information see https://www.esrl.noaa.gov/psd/eddi/.

This is a basic example which shows you how to get EDDI data for Nov 29, 2018 at the one month timescale:


eddi_data <- get_eddi(date = "2018-11-29", timescale = "1 month")
#> class      : RasterStack 
#> dimensions : 224, 464, 103936, 1  (nrow, ncol, ncell, nlayers)
#> resolution : 0.125, 0.125  (x, y)
#> extent     : -125, -67, 25, 53  (xmin, xmax, ymin, ymax)
#> crs        : +init=epsg:4326 +proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0 
#> names      : EDDI_ETrs_01mn_20181129

This will always return a RasterStack object with each layer in the stack corresponding to a date, that can be visualized using raster::plot. Here, large positive values indicate exceptionally dry conditions, and large negative values indicate exceptionally wet conditions, with values of 0 indicating median EDDI values.

color_pal <- colorRampPalette(c("blue", "lightblue", "white", "pink", "red"))
raster::plot(eddi_data, col = color_pal(255), main = "EDDI data for 2018-11-29")

EDDI Resources

A user guide for EDDI can be found here: https://www.esrl.noaa.gov/psd/eddi/pdf/EDDI_UserGuide_v1.0.pdf

For the science behind EDDI, see these two papers: