The NDMC's newly launched National Drought Atlas (NDA) will be highlighted and given the focus of this presentation. Building off the concept of the original National Electronic Drought Atlas (NEDA) developed by the United States Army Corps of Engineers (led by Hoskings, Wallis and Guttman in the early 1990s), the original NEDA consisted of approximately 1000 stations taken from the Historical Climate Network (HCN). The period of record was limited at that time with most stations only having digital data from the late 1940s to present.
For the NDMC's NDA, more than 12,000 stations with precipitation and/or temperature records from the National Weather Service Cooperative data (COOP) network were analyzed through the Regional Climate Centers' (RCCs) Applied Climate Information System (ACIS). From the initial sample set of 12,000 sites considered, over 3000 stations had at least 40 years of data and over 1700 sites had over 60 years of data meeting our criteria. A unique period of record (POR) was established for each station based on the screening criteria, with each station having a unique starting date. From the final selection of 3059 stations, all have at least 40+ years of data and 827 sites contain over 80+ years of data. In essence, the new NDA tripled the size and doubled the period of record of those sites used in the original NEDA. In addition, a cluster analysis of all the stations was conducted to develop homogenous climate regimes. As a result, 139 unique clusters were developed with the average cluster size being 22 stations.
Building off of feedback from the user community, the SPI, SPEI, PDSI, sc-PDSI, Deciles and other climatology (to also include hydrology) is included in the new drought atlas along with a series of visualization tools and weekly maps for every year back to the early 1900's. It is anticipated that this tool will heighten awareness and enhance decision support activities with regards to drought risk for policy makers, resource managers, media and the public.