Olawoyin (2026) Long‐Term Evolution of Rainfall Extremes and Land–Atmosphere Interactions in the Volta River Basin Using Multi‐Source Satellite Observations

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Identification

• Journal: International Journal of Climatology
• Year: 2026
• Date: 2026-09-20
• Authors: Rachel Olawoyin
• DOI: 10.1002/joc.70604

Research Groups

Information not available in the provided text.

Short Summary

This study assesses rainfall extremes and land-atmosphere interactions in the Volta River Basin from 2000 to 2024, revealing pronounced spatial hydro-climatic contrasts but limited evidence for basin-wide temporal intensification of extremes.

Objective

• To assess rainfall extremes and coupled land-surface responses across the Volta River Basin, West Africa.

Study Configuration

• Spatial Scale: Volta River Basin, West Africa.
• Temporal Scale: 2000–2024 (25 annual observations).

Methodology and Data

• Models used:
  • ETCCDI-style indices: Consecutive dry days (CDD), consecutive wet days (CWD), Rx1day (maximum 1-day precipitation), Rx5day (maximum 5-day precipitation), R95p (precipitation from very wet days).
  • Hamed-Rao Modified Mann-Kendall test with Sen's slope for trend inference.
  • Benjamini-Hochberg false-discovery-rate adjustment.
• Data sources:
  • CHIRPS precipitation (daily)
  • MODIS-derived Normalised Difference Vegetation Index (NDVI)
  • MODIS-derived evapotranspiration (ET)
  • MODIS-derived land surface temperature (LST)
  • MODIS-derived Crop Water Stress Index (CWSI)
  • GPM IMERG (for monthly precipitation validation, 2015–2024)
  • ERA5-Land (for monthly precipitation validation, 2015–2024)

Main Results

• Annual rainfall showed no significant monotonic trend (Sen's slope = 4.11 mm per year, modified p = 0.168).
• Rainfall extreme indices (R95p, Rx1day, Rx5day) increased at a nominal p < 0.05, but none remained statistically significant after false-discovery-rate correction.
• CDD, CWD, NDVI, ET, LST, and CWSI showed no statistically significant long-term trend under the autocorrelation-adjusted test.
• Full-series correlations between variables were substantially weaker than estimates based on six snapshot years.
• Monthly validation for 2015–2024 showed close agreement between CHIRPS and GPM IMERG (R = 0.993, R² = 0.986, RMSE = 9.35 mm, bias = -0.96 mm; n = 120) and strong agreement with ERA5-Land (R = 0.958, R² = 0.917).
• The study demonstrates pronounced spatial hydro-climatic contrasts across the basin.
• Evidence for basin-wide temporal intensification of hydro-climatic variables is more limited than suggested by analyses based on sparse years.

Contributions

• Provides a comprehensive assessment of hydro-climatic variability and land-atmosphere interactions over the Volta River Basin using a 25-year dataset.
• Utilizes robust statistical methods, including autocorrelation adjustment and false-discovery-rate correction, to provide more reliable trend inferences compared to previous sparse-year analyses.
• Highlights the importance of considering spatial heterogeneity and the limitations of inferring basin-wide temporal intensification from limited data.
• Validates CHIRPS precipitation data against GPM IMERG and ERA5-Land for the region, confirming its suitability for such studies.

Funding

Information not available in the provided text.

Citation

@article{Olawoyin2026LongTerm,
  author = {Olawoyin, Rachel},
  title = {Long‐Term Evolution of Rainfall Extremes and Land–Atmosphere Interactions in the Volta River Basin Using Multi‐Source Satellite Observations},
  journal = {International Journal of Climatology},
  year = {2026},
  doi = {10.1002/joc.70604},
  url = {https://doi.org/10.1002/joc.70604}
}