Climate Teleconnections Between El Niño-Southern Oscillation and Regional Drought Patterns
DOI:
https://doi.org/10.5281/zenodo.22818579Keywords:
ENSO, El Niño, La Niña, teleconnection, drought, Standardized Precipitation Index, SPEI, Oceanic Niño Index, southern Africa, Horn of Africa, Australia, US SouthwestAbstract
El Niño-Southern Oscillation (ENSO) is the dominant source of interannual climate variability worldwide, but the
strength, sign, and seasonal timing of its influence on drought differ markedly by region, limiting the direct transfer of
forecast skill from one teleconnected area to another. We quantified ENSO-drought teleconnections across four
regions with documented sensitivity to ENSO phase, southern Africa, eastern Australia, the US Southwest, and the
Horn of Africa, using the Oceanic Niño Index (ONI) and gridded precipitation and temperature records spanning
1951-2023 to compute six-month Standardized Precipitation Index (SPI-6) and Standardized Precipitation
Evapotranspiration Index (SPEI-6) values at 0.5-degree resolution, correlating regionally averaged drought indices
against concurrent and lagged ONI at monthly lags of 0 to 6 months. Southern Africa showed the strongest and
most consistent teleconnection, with SPEI-6 during the austral summer wet season correlated with concurrent ONI
at r=-0.61 (p<0.001), indicating El Niño years are reliably drier. The Horn of Africa short-rains season showed a
comparably strong but opposite-signed relationship (r=+0.54), consistent with El Niño-driven wetting historically
offset by more frequent long-rains failure. Eastern Australia and the US Southwest showed weaker but significant
relationships (r=-0.43 and r=-0.38), with the US Southwest teleconnection strongest during boreal winter and
appreciably weaker outside that season. Composite analysis of the seven strongest El Niño and seven strongest La
Niña years since 1951 confirmed these patterns and showed that drought severity, not just occurrence, scaled with
ONI magnitude in three of the four regions, southern Africa, the Horn of Africa, and eastern Australia, but not
significantly in the US Southwest. These results support region-specific rather than globally uniform ENSO-based
seasonal drought early-warning thresholds.
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