Metadata

If you have any questions, comments, or feedback on the objective blends, please email the NDMC at: DroughtMonitor@unl.edu

NDMC Short-Term Composite Drought Index
  • Standardized Precipitation Index (SPI) short-term mix comprised of inputs from 1 to 4 months.
  • Standardized Precipitation Evapotranspiration Index (SPEI) short-term mix comprised of inputs from 1 to 4 months.
  • Vegetation short-term mix is comprised of Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI).
  • Standardized Net Moisture Balance Index (SNMBI) short-term mix has values out to 4 months.
  • Soil Moisture short-term mix is comprised of 40 cm to 100 cm values up to 2 weeks.
NDMC Long-Term Composite Drought Index
  • SPI long-term mix comprised of inputs from 12 to 36 months.
  • SPEI long-term mix comprised of inputs from 12 to 36 months.
  • SNMBI long-term mix comprised of values from 12 to 36 months.
  • Soil Moisture long-term mix is comprised of 100 cm to 200 cm values up to 2 months.
Notes
  • The SNMBI is the NDMC’s experimental expansion of the SPEI to account for snow water equivalent (SWE).
  • SPEI used in the new composite drought indices is based on the Penman-Monteith Potential evapotranspiration, PET (alfalfa reference) provided by the University of California, Merced, as opposed to the Thornthwaite PET in the legacy objective blends.
  • To account for climate non-stationarity, the NDMC developed the short-term indices based on a 40-year period of record (POR) with a 30-year reference mean.
  • To account for climate non-stationarity, the NDMC developed the long-term indices based on a 60-yr period of record POR and 30-year mean reference.
Sources
  • Precipitation and temperature data are from the Applied Climate Information System (ACIS) PRISM model (current) and the Northeast Regional Climate Center (NRCC) model (archive).
  • PET/SWE values are from the University of California, Merced GridMET model (current), and the LIVNEH model CDR (archive).
  • Soil moisture is from the North American Land Data Assimilation System (NLDAS) NOAH model (current), and the Global Land Data Assimilation System (GLDAS) NOAH model (archive).
  • NDVI/EVI are from EROS Visible Infrared Imaging Radiometer Suite (EVIIRS) (current), and the Advanced Very High Resolution Radiometer (AVHRR) Climate Data Record (CDR) (archive).