The Drought Risk Atlas wanted to take concepts and ideas that were put into the original Drought Atlas in the early 1990’s by Hoskings, Wallis and Guttman and take them in a new direction.  The original Drought Atlas had roughly 1,000 stations and the period of record for most was from the 1940s on.  The data analyzed for this project consisted of the Historical Climate Network (HCN) data, and estimates were used in places.  A monthly time step was used to calculate the Palmer Drought Severity Index (PDSI). 

In the concept for the new Drought Risk Atlas, we wanted to scan the digitized data for the most complete, long term weather stations in the country.  We also wanted to capitalize on calculating several drought indices using a weekly time step, for multiple periods.

Station Criteria

Learn how the stations used in the atlas were chosen.

Cluster Analysis

An explanation of how the stations were grouped into clusters.

L Moments

An overview of the parameters used to calculate the L moments for the atlas.


An explanation of the indices derived from the data used in the atlas.


A description of how the trends were calculated.