The Saharan Oscillation Index (1950-2024): Statistical Characterization, Persistence, and Spectral Variability
Abstract
This study presents a comprehensive statistical and spectral characterization of the Saharan Oscillation Index (SaOI), an atmospheric circulation metric describing the standardized sea-level pressure difference between the Azores High and the Saharan depression over the 1950–2024 period. Using monthly SaOI values derived from ERA5 reanalysis, we assessed distributional properties, temporal persistence, spectral variability, time-frequency structure, and long-term trends using complementary time-series methods. The SaOI exhibits a near-Gaussian central distribution (µ = 0.1954, σ = 0.1137). Although the original monthly series shows moderate lag-1 autocorrelation (r ≈ 0.50), lag-1 autocorrelation is substantially reduced after removal of the climatological seasonal cycle (r₁ = 0.128), indicating weak residual month-to-month dependence. Fourier and wavelet analyses identify the annual cycle as the dominant component of variability, with a weaker semi-annual component, whereas no distinct persistent narrow-band interannual oscillation is evident. A weak positive long-term trend is detected (Sen’s slope = 0.0004 units yr⁻¹), but it is not statistically significant after accounting for serial dependence (p ≈ 0.17). These results establish a reproducible statistical baseline for interpreting SaOI variability and provide a foundation for subsequent investigations of its teleconnections and regional climate impacts.
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BibTeX
@misc{tebbaai2026saharan,
title = {{The Saharan Oscillation Index (1950-2024): Statistical Characterization, Persistence, and Spectral Variability}},
author = {Younes TEBBAAI and Kenza KHOMSI and Mohamed KHALIS},
howpublished = {Research Square},
year = {2026},
month = oct,
doi = {10.21203/rs.3.rs-10768050/v1},
url = {https://doi.org/10.21203/rs.3.rs-10768050/v1},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - The Saharan Oscillation Index (1950-2024): Statistical Characterization, Persistence, and Spectral Variability
AU - Younes TEBBAAI
AU - Kenza KHOMSI
AU - Mohamed KHALIS
PY - 2026
DA - 2026/10/28
PB - Research Square
DO - 10.21203/rs.3.rs-10768050/v1
UR - https://doi.org/10.21203/rs.3.rs-10768050/v1
AB - This study presents a comprehensive statistical and spectral characterization of the Saharan Oscillation Index (SaOI), an atmospheric circulation metric describing the standardized sea-level pressure difference between the Azores High and the Saharan depression over the 1950–2024 period. Using monthly SaOI values derived from ERA5 reanalysis, we assessed distributional properties, temporal persistence, spectral variability, time-frequency structure, and long-term trends using complementary time-series methods. The SaOI exhibits a near-Gaussian central distribution (µ = 0.1954, σ = 0.1137). Although the original monthly series shows moderate lag-1 autocorrelation (r ≈ 0.50), lag-1 autocorrelation is substantially reduced after removal of the climatological seasonal cycle (r₁ = 0.128), indicating weak residual month-to-month dependence. Fourier and wavelet analyses identify the annual cycle as the dominant component of variability, with a weaker semi-annual component, whereas no distinct persistent narrow-band interannual oscillation is evident. A weak positive long-term trend is detected (Sen’s slope = 0.0004 units yr⁻¹), but it is not statistically significant after accounting for serial dependence (p ≈ 0.17). These results establish a reproducible statistical baseline for interpreting SaOI variability and provide a foundation for subsequent investigations of its teleconnections and regional climate impacts.
SN - 2693-5015
ER -