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<p>The Saharan Oscillation Index (SaOI) quantifies the pressure gradient between the Azores High and the Saharan low centered near Niamey, capturing atmospheric variability that influences climate across the Euro-Atlantic-African region. Despite its importance for regional hydroclimate, dust transport, and air quality, its phase behavior and teleconnections with global climate modes remain insufficiently characterized. Here, we analyze 75 years (1950–2024) of SaOI variability using standardized phase classification and seasonal lag-correlation analysis with thirteen large-scale climate indicators (LSCIs). The SaOI exhibits three distinct periods: a balanced phase distribution (1950–1965), sustained variability (1965–1990), and a pronounced shift toward positive-neutral dominance after 1990, with a marked decline in negative phase frequency after 2010. The SaOI shows moderate but statistically significant correlations with the North Atlantic Oscillation Index (NAOI; <i>r</i> = 0.42, 95% CI [0.21, 0.59]), Arctic Oscillation Index (AOI; <i>r</i> = 0.42, 95% CI [0.21, 0.59]), and Oceanic Niño Index (ONI; <i>r</i> = -0.44, 95% CI [-0.61, -0.24]). These relationships explain approximately 18–19% of the interannual variance, indicating meaningful but not strong coupling within a multifactorial climate system. Seasonal analysis further reveals lagged teleconnections extending from late winter through summer, highlighting the combined influence of extratropical and tropical processes on Saharan circulation. Positive SaOI phases are associated with enhanced pressure gradients that strengthen trade winds, suppress precipitation, and increase dust activity, whereas negative phases promote moisture advection and convective activity. The apparent regime shift after 1990 suggests potential non-stationarity, possibly driven by anthropogenic forcing and/or natural multidecadal variability, although formal change-point verification using non-parametric methods is beyond the scope of this study. These findings establish the SaOI as a useful diagnostic tool for subseasonal-to-seasonal prediction, with direct applications in drought early warning, dust storm forecasting, and heat-risk preparedness across the Sahel, Maghreb, and Mediterranean regions.</p>

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The Saharan oscillation index (1950–2024): phase structure, regime shifts, and global teleconnections

  • 期刊论文

  • 发表日期：

    2026年5月15日

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  • Younes Tebbaai,
  • Kenza Khomsi,
  • Mohamed Khalis

摘要

The Saharan Oscillation Index (SaOI) quantifies the pressure gradient between the Azores High and the Saharan low centered near Niamey, capturing atmospheric variability that influences climate across the Euro-Atlantic-African region. Despite its importance for regional hydroclimate, dust transport, and air quality, its phase behavior and teleconnections with global climate modes remain insufficiently characterized. Here, we analyze 75 years (1950–2024) of SaOI variability using standardized phase classification and seasonal lag-correlation analysis with thirteen large-scale climate indicators (LSCIs). The SaOI exhibits three distinct periods: a balanced phase distribution (1950–1965), sustained variability (1965–1990), and a pronounced shift toward positive-neutral dominance after 1990, with a marked decline in negative phase frequency after 2010. The SaOI shows moderate but statistically significant correlations with the North Atlantic Oscillation Index (NAOI; r = 0.42, 95% CI [0.21, 0.59]), Arctic Oscillation Index (AOI; r = 0.42, 95% CI [0.21, 0.59]), and Oceanic Niño Index (ONI; r = -0.44, 95% CI [-0.61, -0.24]). These relationships explain approximately 18–19% of the interannual variance, indicating meaningful but not strong coupling within a multifactorial climate system. Seasonal analysis further reveals lagged teleconnections extending from late winter through summer, highlighting the combined influence of extratropical and tropical processes on Saharan circulation. Positive SaOI phases are associated with enhanced pressure gradients that strengthen trade winds, suppress precipitation, and increase dust activity, whereas negative phases promote moisture advection and convective activity. The apparent regime shift after 1990 suggests potential non-stationarity, possibly driven by anthropogenic forcing and/or natural multidecadal variability, although formal change-point verification using non-parametric methods is beyond the scope of this study. These findings establish the SaOI as a useful diagnostic tool for subseasonal-to-seasonal prediction, with direct applications in drought early warning, dust storm forecasting, and heat-risk preparedness across the Sahel, Maghreb, and Mediterranean regions.