U.S. Drought Monitor

Drought Severity and Coverage Index

The Drought Severity and Coverage Index is an experimental method for converting drought levels from the U.S. Drought Monitor map to a single value for an area. DSCI values are part of the U.S. Drought Monitor data tables. If you want to compute it yourself, using cumulative Drought Monitor data, add the values for D0 through D4 to get the Drought Severity and Coverage Index. Possible values of the DSCI are from 0 to 500. Zero means that none of the area is abnormally dry or in drought, and 500 means that all of the area is in D4, exceptional drought. Or, to see more math, use categorical (not cumulative) Drought Monitor data, and compute a weighted sum:

1(D0) + 2(D1) + 3(D2) + 4(D3) + 5(D4) = DSCI


1(33.75) + 2(14.50) + 3(29.26) + 4(21.69) + 5(.39) = 33.75 + 29 + 87.78 + 86.76 + 1.95 = 239

The utility of the DSCI has not yet been widely tested but it provides a convenient way to convert USDM data from categorical to continuous, and to aggregate from spatially specific to geopolitical boundaries.

Aggregation over time

People also ask about how to aggregate the U.S. Drought Monitor over time. With the caveat that reducing a series of spatial depictions to a single numeric value inevitably leads to quite a bit of information loss, we recommend summing the DSCI over n weeks to get the Accumulated DSCI (ADSCI).

Example for five weeks

239 + 238 + 293 + 295 + 293 = 1358


The idea for the Drought Severity and Coverage Index is courtesy of Adnan Akyuz, North Dakota State University. Suggested citation:

Akyuz, F. A. 2017. Drought Severity and Coverage Index. United States Drought Monitor. https://droughtmonitor.unl.edu/About/AbouttheData/DSCI.aspx