The eddi R package facilitates access to the NOAA Evaporative Demand Drought Index (EDDI) data product.
Install the most recently released version of the eddi package from CRAN:
Or, you can install the development version of eddi with 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:
library(eddi) eddi_data <- get_eddi(date = "2018-11-29", timescale = "1 month") eddi_data #> 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.
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: