An Open-Data Point-Location Drought Benchmark for Australia: SPI–SPEI Variability, Persistence, and Warming-Amplification Analysis Using SILO Data

Veysel Süleyman Yavuz

Abstract

Australia’s drought risk is shaped by both precipitation deficits and atmospheric water demand, but long-term comparisons are sensitive to drought-index formulation, PET choice, and hotspot-weighting assumptions. This study develops an open-data point-location drought benchmark for Australia using daily SILO DataDrill records from nine selected locations for 1900–2025. Monthly hydroclimatic variables were derived from rainfall, temperature, SILO FAO56 short-crop reference PET, and Morton PET for sensitivity analysis. SPI-12 was calculated from 12-month precipitation accumulation using gamma distribution fitting, while SPEI-12 was calculated from 12-month climatic water balance using generalized logistic distribution fitting. Drought-event metrics, persistence indicators, Hamed–Rao modified Mann–Kendall and Sen’s slope tests, SPI–SPEI divergence metrics, and a sensitivity-tested composite hotspot score were used to compare drought behaviour among locations. Results showed strong cross-location differences in drought frequency, duration, severity, persistence, and warming-amplified drought stress. FAO56 PET improved the physical consistency of water-balance drought assessment relative to temperature-only PET formulations. SPI–SPEI divergence was most pronounced at Alice Springs, whereas Perth and Adelaide showed the most robust high hotspot ranks due to combined severity, persistence, and recent drought-month concentration. Random-weight sensitivity analysis confirmed Perth and Adelaide as the most stable top-ranked locations. The study provides a transparent benchmark for point-location drought comparison and a foundation for future gridded drought-risk assessment in Australia.

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