Banda et al. (2026) A Multi-Metric and Multi-Driver Analysis of Long-Term Aridity Change over Africa (1951-2020)

Identification

• Journal: Journal of Geoscience and Environment Protection
• Year: 2026
• Date: 2026-01-01
• Authors: Noel Banda, Tanimu Abubakar Sadiq, Tianyu Wang, Nyasulu Matthews
• DOI: 10.4236/gep.2026.142009

Research Groups

• School of Atmospheric Science, Nanjing University of Information Science and Technology (NUIST), Nanjing, China
• Department of Climate Change and Meteorological Services (DCCMS), Blantyre, Malawi
• Nigerian Meteorological Agency (NiMet), Nnamdi Azikiwe International Airport, Abuja, Nigeria
• State Key Laboratory of Climate System Prediction and Risk Management/Key Laboratory of Meteorological Disaster, Ministry of Education/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters/Institute for Climate and Application Research/Jiangsu Key Laboratory of Intelligent Weather Forecasting and Applications Based on Big Data, Nanjing University of Information Science and Technology, Nanjing, China
• School of Ecology and Applied Meteorology, Nanjing University of Information Science and Technology (NUIST), Nanjing, China

Short Summary

This study analyzed long-term aridity changes across Africa from 1951-2020, revealing widespread drying trends primarily driven by increasing potential evapotranspiration (PET) due to warming temperatures, with precipitation playing a secondary role.

Objective

• To assess the climatic components of growing aridification in Africa using a multi-metric framework (Aridity Index, precipitation, and potential evapotranspiration) from 1951-2020.
• To quantify the magnitude and spatial extent of dryness changes and attribute these changes to potential evapotranspiration and its components.
• To assess whether aridity patterns are shifting and expanding across Africa.

Study Configuration

• Spatial Scale: African continent, subdivided into North Africa, West Africa, East Africa, and Southern Africa. Data processed on a 0.1° × 0.1° grid.
• Temporal Scale: 1951-2020 (70 years), analyzed annually and seasonally (DJF, MAM, JJA, SON). Aridity category shifts analyzed between 1951-1984 and 1985-2020.

Methodology and Data

• Models used:
  • Aridity Index (AI = P/PET) based on the United Nations Environment Programme (UNEP) classification scheme.
  • FAO Penman-Monteith method for Potential Evapotranspiration (PET) calculation.
  • Ordinary Least Squares (OLS) for linear trend analysis, with statistical significance assessed at p < 0.05.
  • Decomposition of PET changes into contributions from temperature, available energy, relative humidity, and wind speed.
  • Decomposition of AI changes into contributions from precipitation and PET.
• Data sources:
  • Precipitation: Global Precipitation Climatology Centre (GPCC) full data Monthly Version 2023 (0.25° × 0.25° resolution).
  • Potential Evapotranspiration (PET) components (surface net radiation, relative humidity, wind speed): ERA5-Land reanalysis dataset (0.1° × 0.1° resolution).
  • Precipitation data regridded to match ERA5-Land resolution (0.1° × 0.1°) using linear interpolation.

Main Results

• Widespread drying trends were observed across 88.9% of Africa, with 43% showing statistically significant drying (p < 0.05).
• The mean decline in the Aridity Index (AI) over the continent was -0.0012 per year, corresponding to an 8.4% reduction over the 70-year period.
• Increasing potential evapotranspiration (PET) emerged as the dominant driver of drying, with significant trends covering 85.7% of the continent, compared to precipitation-driven drying which covered roughly 20.3%.
• Decomposition of PET indicated that warming temperatures were the main driver of rising atmospheric moisture demand, explaining 82.1%-98.4% of the PET increase.
• Accelerated dryland expansion was evident since 1985, particularly over southern, eastern, and western Africa, with shifts from humid/dry sub-humid to semi-arid, and semi-arid to arid conditions.
• Regional variations in drying mechanisms were identified:
  • West and East Africa: Aridification primarily influenced by rising PET due to warming and declining relative humidity.
  • Southern Africa: Aridification largely controlled by precipitation deficits.
  • North Africa: Annual drying driven by precipitation deficits, but PET (due to warming and declining humidity) dominated during the SON season.
• East Africa exhibited a complex pattern, with seasonal moistening during SON despite an overall drying trend.

Contributions

• Provides a comprehensive multi-metric and multi-driver analysis of long-term aridity change across Africa, quantifying the extent and attributing the drivers of dryness.
• Highlights the critical role of warming-induced increases in potential evapotranspiration as the primary driver of aridification across most of Africa, often overshadowing precipitation changes.
• Identifies significant regional discrepancies in the dominant drivers of aridification, emphasizing the need for tailored adaptation strategies.
• Demonstrates persistent shifts in aridity categories across various regions, indicating long-term climate change rather than short-term variability.

Funding

• Malawi Government, through the Department of Climate Change and Meteorological Services (DCCMS)
• Nanjing University of Information Science & Technology
• Ministry of Commerce of the People’s Republic of China (MOFCOM) scholarship

Citation

@article{Banda2026MultiMetric,
  author = {Banda, Noel and Sadiq, Tanimu Abubakar and Wang, Tianyu and Matthews, Nyasulu},
  title = {A Multi-Metric and Multi-Driver Analysis of Long-Term Aridity Change over Africa (1951-2020)},
  journal = {Journal of Geoscience and Environment Protection},
  year = {2026},
  doi = {10.4236/gep.2026.142009},
  url = {https://doi.org/10.4236/gep.2026.142009}
}