EDDI is a drought indicator that uses atmospheric evaporative demand (E0) anomalies across a time-window of interest relative to its climatology to indicate the spatial extent and severity of drought. This page provides access to near-real-time (with a five-day latency, i.e., the most recent information is five days old) EDDI plots with time windows integrating E0 anomalies from 1 to 12 weeks and 1 to 12 months from the most current date. E0 is calculated using the Penman Monteith FAO56 reference evapotranspiration formulation driven by temperature, humidity, wind speed, and incoming solar radiation from the North American Land Data Assimilation System (NLDAS-2) dataset. For a particular time-window, EDDI is estimated by standardizing the E0 anomalies relative to the whole period of the record (1979-present), using a non-parametric method (see Hobbins et al., 2016). For plotting purposes, EDDI values are binned into different percentile categories analogous to the US Drought Monitor plots. However, in case of EDDI plots, both drought and anomalously wet categories are shown. EDDI data are available at a ~12-km resolution across CONUS since January 1, 1980, and are updated daily.
EDDI has the potential to offer early warning of agricultural drought, hydrologic drought, and fire-weather risk by providing real-time information on the emergence or persistence of anomalous evaporative demand in a region. A particular strength of EDDI is in capturing the precursor signals of water stress at weekly to monthly timescales, which makes EDDI a strong tool for drought preparedness at those timescales.
