Raji et al. (2026) Coupled land–atmosphere processes exacerbate recent compound drought and heatwaves over Africa

Identification

• Journal: The Science of The Total Environment
• Year: 2026
• Authors: Ibraheem Raji, Akintomide A. Akinsanola, Thierry N. Taguela
• DOI: 10.1016/j.scitotenv.2026.181452

Research Groups

• Department of Earth and Environmental Sciences, University of Illinois Chicago, Chicago, IL, USA.

Short Summary

This study identifies a significant intensification of compound drought and heatwave (CDHW) events in equatorial Africa since 2004, driven by a shift toward moisture-limited land–atmosphere coupling and weakened atmospheric vertical motion. The research highlights how self-reinforcing feedback loops between soil moisture depletion and surface warming exacerbate climate extremes in the region.

Objective

• To evaluate recent spatiotemporal trends in CDHW occurrences across Africa and diagnose the underlying physical drivers, including land–atmosphere feedbacks and large-scale climate teleconnections.

Study Configuration

• Spatial Scale: Continental Africa, with a high-resolution focus on an equatorial hotspot (12°S–15°N, 10°E–48°E) covering countries such as the Democratic Republic of the Congo, Ethiopia, and Kenya.
• Temporal Scale: 1980–2024, subdivided into Period 1 (P1: 1980–2003) and Period 2 (P2: 2005–2024) based on a detected change point in 2004.

Methodology and Data

• Models used: ERA5 reanalysis (0.25° resolution) and NCEP-2 reanalysis (2.5° resolution).
• Data sources: Satellite-derived and reanalysis fields for temperature, soil moisture, radiation, and winds; CRU TS v4.09 gridded observations for validation; NOAA climate indices (AMO, IOD, PDO, ENSO).
• Analytical Framework:
  • CDHW identification using the 3-month Standardized Precipitation Evapotranspiration Index (SPEI-3 < -1) and the 95th percentile of daily maximum temperature ($T_{max}$).
  • Surface Energy Budget (SEB) and Moisture Budget decomposition.
  • Soil moisture–temperature coupling strength ($\pi$) and Evaporative Fraction (EF) analysis.
  • Stepwise multiple regression to quantify teleconnection influences.

Main Results

• CDHW Intensification: Equatorial Africa is a major hotspot where CDHW frequency increased by 0.9 events per decade, duration by 1.2 days per decade, and magnitude by 0.4 °C per decade.
• Regime Shift: A statistically significant change point occurred in 2004; the post-2004 period (P2) saw a rapid intensification rate of 1.1 events per decade compared to 0.4 in P1.
• Land–Atmosphere Drivers: The intensification is driven by a shift from energy-limited to moisture-limited regimes. Drier soils (reduced by ~0.6 mm/day in precipitation) limit evaporative cooling, increasing sensible heat flux and surface temperatures.
• Energy and Moisture Budgets: Recent warming is primarily due to increased net downward radiation ($+0.5$ °C contribution), specifically clear-sky longwave radiation. Drying is linked to a weakened vertical dynamic term caused by reduced diabatic heating, which suppresses deep convection.
• Climate Teleconnections: The Atlantic Multidecadal Oscillation (AMO) and Indian Ocean Dipole (IOD) are the dominant large-scale drivers, jointly explaining 58.7% of the variance in CDHW frequency during the recent period.

Contributions

• Provides a comprehensive physical diagnosis of the mechanisms (energy and moisture budgets) driving compound extremes specifically in the African context.
• Identifies a critical temporal shift (2004) in African climate extremes, moving toward a more coupled and aridity-prone land–atmosphere state.
• Quantifies the increasing role of the drought–heatwave interaction effect relative to individual extremes in driving compound events.

Funding

• Not explicitly mentioned in the provided text (Acknowledgments cite the National Center for Atmospheric Research (NCAR) and the European Centre for Medium-Range Weather Forecasts (ECMWF) for data access).

Citation

@article{Raji2026Coupled,
  author = {Raji, Ibraheem and Akinsanola, Akintomide A. and Taguela, Thierry N.},
  title = {Coupled land–atmosphere processes exacerbate recent compound drought and heatwaves over Africa},
  journal = {The Science of The Total Environment},
  year = {2026},
  doi = {10.1016/j.scitotenv.2026.181452},
  url = {https://doi.org/10.1016/j.scitotenv.2026.181452}
}

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