National Drought Mitigation Center Composite Drought Indicators

The National Drought Mitigation Center has developed Composite Drought Indicators that have been released experimentally. These long-term and short-term indicators were developed from an earlier effort developed in 2002 using climate division based data to provide a weekly assessment of short- and long-term drought using consistent inputs and weights. The NDMC worked to transfer these data to finer resolution gridded data in 2021 in an effort to mimic the original scope of the short- and long-term products. 

In 2022, the NDMC began using machine learning techniques utilizing a library of digital datasets to improve upon and enhance the weekly short- and long-term composite drought indicators. The experimental products were released in October 2023 to the public, and research is ongoing to refine and enhance these tools and to incorporate seasonality and regionality into the products. As part of the process, various approaches to account for non-stationarity were explored. 

In the end, the short-term indices were based on a 40-year period of record with a 30-year reference mean, and the long-term indices were based on a 60-year period of record and 30-year mean reference. 

These products have been released experimentally to the drought monitoring community and the NDMC is incorporating feedback and validation information through an ongoing process and stakeholders can provide this information to DroughtMonitor@unl.edu.