Ogunrinde et al. (2026) Evaporative demand drought index for monitoring and analyzing drought conditions in arid regions of Asia and Africa

Identification

• Journal: Weather and Climate Extremes
• Year: 2026
• Date: 2026-02-18
• Authors: Akinwale T. Ogunrinde, Paul Adigun, Xian Xue, Dairaku Koji, Ermias Sisay Brhane
• DOI: 10.1016/j.wace.2026.100873

Research Groups

• Key Laboratory of Ecological Safety and Sustainable Development in Arid Lands, Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, Lanzhou, Gansu, China
• Department of Engineering Mechanics and Energy, University of Tsukuba, Tsukuba, Japan

Short Summary

This study introduces and evaluates the Evaporative Demand Drought Index (EDDI) as a complementary tool for monitoring flash droughts and evapotranspiration-driven moisture stress in arid regions of Asia and Africa, demonstrating its ability to detect drought onset weeks earlier than precipitation-based indices.

Objective

• To introduce and evaluate the Evaporative Demand Drought Index (EDDI) as a complementary tool for monitoring flash droughts and evapotranspiration-driven moisture stress in arid regions of Asia and Africa, comparing its performance with precipitation-based indices (SPI, SPEI) across multiple timescales.

Study Configuration

• Spatial Scale: Arid regions of Asia and Africa, including Sahara (SAH), Mediterranean (MED), Arabian Peninsula (ARP), West Central Asia (WCA), Eastern Europe (EEU), West Siberia (WSB), East Siberia (ESB), East Central Asia (ECA), and Tibetan Plateau (TIB), spanning approximately 10° to 50°N latitude and 15° to 125°E longitude.
• Temporal Scale: 1983 to 2023, with drought indices calculated across timescales from sub-weekly to 12 months.

Methodology and Data

• Models used:
  • Evaporative Demand Drought Index (EDDI) based on Penman-Monteith formulation (ASCE standardized equation) for reference evapotranspiration (ETo).
  • Standardized Precipitation Index (SPI) based on precipitation data fitted to a gamma distribution.
  • Standardized Precipitation-Evapotranspiration Index (SPEI) based on climatic water balance (precipitation minus ETo) fitted to a log-logistic distribution.
  • Modified Mann-Kendall test for trend analysis.
  • Sen's slope estimator for trend magnitude.
  • Spearman's rank correlation coefficient for inter-index relationships.
  • Run theory for drought characterization (duration, severity, intensity, peak, frequency).
• Data sources: ERA5-Land reanalysis datasets at 0.1° × 0.1° resolution for precipitation, surface mean air temperature, dewpoint temperature, surface net solar radiation, and wind speed.

Main Results

• EDDI exhibited strong inverse correlations with SPI and SPEI, ranging from −0.41 to −0.91, with the strongest association (−0.91) observed between EDDI and SPEI at the 1-month scale in the Sahara region.
• EDDI revealed more pronounced drying trends across arid domains compared to SPI or SPEI, attributed to significant increases in temperature (0.02–0.05 °C per year) and reference evapotranspiration (ETo) (2.0–5.16 mm per year).
• Drought frequency intensified in most regions after 2000, with the exception of the Tibetan Plateau.
• During the 2010 drought event, EDDI detected drought onset weeks earlier than SPI in regions like the Arabian Peninsula and Sahara, demonstrating its sensitivity to rapid increases in evaporative demand.
• EDDI identified higher frequencies of moderate-to-extreme drought categories (C2–C4) in Eastern Europe compared to SPI, consistent with its response to evaporative anomalies.

Contributions

• Provides a comprehensive, spatially detailed comparison of EDDI performance relative to SPI and SPEI across multiple timescales (1 to 12 months) in extensive and underrepresented arid regions of Asia and Africa.
• Enhances available methods for drought monitoring and early warning by demonstrating EDDI's effectiveness in identifying rapid-onset droughts and its lead time over precipitation-based indices.
• Reinforces the value of EDDI as a complementary and independent index, particularly in environments where atmospheric evaporative demand is a primary driver of drought severity.
• Supports the integration of EDDI into operational drought early warning systems for arid regions to improve monitoring capabilities and inform decision-making for drought risk management under climate change.

Funding

• Northwest Institute of Ecological Environment and Resources, Chinese Academy of Science (grant number: E429020101)

Citation

@article{Ogunrinde2026Evaporative,
  author = {Ogunrinde, Akinwale T. and Adigun, Paul and Xue, Xian and Koji, Dairaku and Brhane, Ermias Sisay},
  title = {Evaporative demand drought index for monitoring and analyzing drought conditions in arid regions of Asia and Africa},
  journal = {Weather and Climate Extremes},
  year = {2026},
  doi = {10.1016/j.wace.2026.100873},
  url = {https://doi.org/10.1016/j.wace.2026.100873}
}