Get Evaporative Demand Drought Index Raster Data

Finds and downloads raw Evaporative Demand Drought Index (EDDI) data, then reads the data into 'R' using the 'raster' package. The EDDI product detects drought at multiple time scales, from weekly "flash droughts" to long-term droughts. More information about the EDDI data product can be found at < https://www.esrl.noaa.gov/psd/eddi/>.

eddi: R package for the NOAA Evaporative Demand Drought Index

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

Installation

You can install the development version of eddi with devtools:

# install.packages("devtools")
devtools::install_github("earthlab/eddi")

Example

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.

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:

M. Hobbins, A. Wood, D. McEvoy, J. Huntington, C. Morton, M. Anderson, and C. Hain (June 2016): The Evaporative Demand Drought Index: Part I – Linking Drought Evolution to Variations in Evaporative Demand. J. Hydrometeor., 17(6), 1745-1761.
D. J. McEvoy, J. L. Huntington, M. T. Hobbins, A. Wood, C. Morton, M. Anderson, and C. Hain (June 2016): The Evaporative Demand Drought Index: Part II – CONUS-wide Assessment Against Common Drought Indicators. J. Hydrometeor., 17(6), 1763-1779.