Bello et al. (2026) Characterization of meteorological drought using SPI and SPEI indices in Kaduna State, Nigeria

Identification

• Journal: Discover Hazards
• Year: 2026
• Date: 2026-01-13
• Authors: N. J. Bello, Suleiman Musa Balarabe, Muhammad Lawal Abubakar
• DOI: 10.1007/s44475-026-00007-6

Research Groups

• Center for Disaster Risk Management, Ahmadu Bello University, Zaria, Nigeria
• Department of Geography and Sustainability Studies, Kaduna State University, Kaduna, Nigeria
• Climate Research Group, Kaduna State University, Kaduna, Nigeria

Short Summary

This study characterized meteorological drought in Kaduna State, Nigeria, from 1981 to 2024 using SPI and SPEI at multiple timescales. It found that warming temperatures and increased evapotranspiration mask precipitation gains, leading to no significant trend in SPEI-based drought despite a wetting trend in SPI, emphasizing SPEI's superiority for drought monitoring in the region.

Objective

• To characterize meteorological drought in Kaduna State, Nigeria, from 1981 to 2024 by extracting key features such as frequency, duration, severity, and intensity of drought events using the Standardized Precipitation Index (SPI) and Standardized Precipitation Evapotranspiration Index (SPEI) at 3, 6, 9, 12, and 24-month timescales.
• To understand the difference between precipitation-driven SPI and temperature-influenced SPEI indices, particularly regarding the impact of warming temperatures on atmospheric water demand in a tropical region.

Study Configuration

• Spatial Scale: Kaduna State, Nigeria (area of 46,053 square kilometres), specifically using data from the Kaduna Synoptic Weather Station.
• Temporal Scale: 1981 to 2024 (44 years).

Methodology and Data

• Models used:
  • Standardized Precipitation Index (SPI)
  • Standardized Precipitation Evapotranspiration Index (SPEI)
  • Hargreaves method (for Potential Evapotranspiration calculation)
  • Run theory (for drought duration, severity, and intensity)
  • Mann–Kendall trend test
  • Standard Normal Homogeneity Test (SNHT) and Buishand tests (for homogeneity)
  • Pearson Product-Moment Correlation Coefficient (R)
  • Mean difference
  • Kling-Gupta Efficiency (KGE)
  • Mean Absolute Error (MAE)
  • Root Mean Square Error (RMSE)
• Data sources: Monthly climate data (rainfall, minimum and maximum temperature) from the Nigerian Meteorological Agency (NiMet), Kaduna Synoptic Weather Station.

Main Results

• Both SPI and SPEI detected drought events, with their duration and severity increasing over longer timescales.
• SPI-3 detected the most intense drought event with a magnitude of -4.317 in March 2000.
• SPEI-3 detected the most severe drought event with a magnitude of -3.355 in June 2015.
• The longest SPI-24 drought lasted 26 months (September 1983–September 1985) with a severity of -3.351.
• The longest SPEI-24 drought lasted 35 months (September 1983–July 1986).
• SPI showed significant wetting trends at 12-month (p = 0.04) and 24-month (p = 0.002) timescales.
• SPEI exhibited no significant trend at any timescale (p > 0.36), indicating that temperature-induced evapotranspiration offset precipitation gains.
• A strong positive correlation (r > 0.94) was observed between SPI and SPEI, particularly at the 6-month timescale.
• SPI and SPEI diverged at short and long timescales, primarily due to the influence of temperature on evapotranspiration.
• Kling-Gupta Efficiency (KGE) values for SPI vs. SPEI indicated varying agreement: -2.072 (3-month), 0.834 (6-month), -0.204 (9-month), -0.661 (12-month), and -0.226 (24-month), revealing significant biases and variability mismatches at most timescales except 6-month.
• The early to mid-1980s (specifically 1983–1986) were identified as a period of extreme drought stress across all SPI and SPEI scales.

Contributions

• Provided a comprehensive characterization of meteorological drought in Kaduna State, Nigeria, using both SPI and SPEI across multiple timescales, addressing a critical knowledge gap in regional drought analysis.
• Demonstrated the utility of the Kling-Gupta Efficiency (KGE) metric in the Nigerian context for a robust assessment of drought index performance, which was a novel application compared to previous regional studies.
• Offered robust statistical evidence that increasing temperature-driven evaporative demand has neutralized precipitation gains, masking a wetting signal detected by precipitation-only indices. This highlights a significant and under-recognized climate change impact in Savanna and semi-arid regions.
• Emphasized the critical need to prioritize temperature-inclusive indices like SPEI over precipitation-only indices for accurate drought monitoring and effective adaptation planning in a warming climate.

Funding

This research did not receive any funding.

Citation

@article{Bello2026Characterization,
  author = {Bello, N. J. and Balarabe, Suleiman Musa and Abubakar, Muhammad Lawal},
  title = {Characterization of meteorological drought using SPI and SPEI indices in Kaduna State, Nigeria},
  journal = {Discover Hazards},
  year = {2026},
  doi = {10.1007/s44475-026-00007-6},
  url = {https://doi.org/10.1007/s44475-026-00007-6}
}