Brian Fuchs, National Drought Mitigation Center, University of Nebraska-Lincoln, Lincoln, NE
Mark Svoboda, National Drought Mitigation Center
Deborah Bathke, National Drought Mitigation Center
Curtis Riganti, National Drought Mitigation Center
The United States Drought Monitor (USDM) (Svoboda et al., 2002) has become the go-to resource for the weekly objective assessment of drought in the United States and continues to be used more and more by stakeholders and federal agencies for a variety of decision-making activities. When the USDM was developed in 1999, the largest limiting factor was the regular availability of data that covered the United States in a near-real time capacity. Only a handful of drought-related indices and indicators were available each week, and most were being disseminated at a very coarse climate division scale. One of the many strengths of the USDM is that the process of making the weekly map has been flexible, allowing it to evolve over time and incorporate new data as they have become available. For the researchers who are developing these new types of data, the USDM in turn enables them to see the data being used in a very useful and scientific manner.
From the early beginnings of using coarse climate-division-based data, the USDM currently is incorporating a number of gridded data that are available at a very high resolution. New tools such as the Evaporative Stress Index (ESI), the Evaporative Demand Drought Index (EDDI), and the Vegetation Drought Response Index (VegDRI), as well as numerous satellite-based products and gridded data products, have allowed the USDM process to evolve to produce the map at a finer resolution than when it started. By adding several dozen sources of subjective data to feed into the “convergence of evidence” approach that is the basis of the strength of the USDM, the USDM process is flexible enough to incorporate any number of inputs into assessments.
Not only has the number of indices and indicators increased since the late 1990s, but the way in which the USDM authors incorporate these data has also evolved. More and more data providers are serving their data in GIS-compatible format. This allows the data to be shared freely, and it also allows for them to be injected into the USDM map development process as various layers of data. Through GIS, the USDM authors are now able to draw the drought intensity contours following the actual data contours in GIS of the dozens of subjective data being utilized. This has increased the accuracy of the map and has also allowed the map to truly follow the data available.
As drought monitoring continues to evolve and new tools become available, the USDM will continue to implement these data and other technological advances to keep pushing the threshold. Drought monitoring has come a long way from using just the Palmer Drought Index in the 1960s and the USDM will be at the forefront of these efforts.