A Daily Evapotranspiration-Based Drought Indicator in Characterizing Spatiotemporal Evolution of Flash Droughts

Droughts cause multiple ecological and social damages. Reliable drought monitoring and forecasting can benefit various sectors by allowing adequate lead times for drought mitigation efforts. Drought indices are key tools to quantify drought severity, but they are currently limited to timescales of monthly or longer. However, shorter-timescale (e.g., daily) drought indices enable more accurate identification of drought characteristics (e.g., onset and cessation time), especially for flash droughts. Here, we propose a daily drought index named daily evapotranspiration deficit index (DEDI) that is constructed based on actual and potential evapotranspiration data. Through comparisons with multiple reference indices and observations, DEDI can well characterize the spatiotemporal evolution of regional drought events that occurred in North China, Southwest China, eastern Northwest China, and Northeast China in the spring and summer of 2019. We have publicly shared the DEDI dataset with a high spatial resolution (0.25°) and a long time series (1979–2022) covering global land areas, available at https://doi.org/10.5281/zenodo.7768534. The dataset has also been validated to have the capability to capture dry and wet variations and to detect ecology- or agriculture-related droughts at a global scale. Overall, the DEDI indicator could be regarded as a practical solution to facilitate flash drought monitoring and early warning.