Associations between tropical cyclone activity in the Southwest Indian Ocean and El Niño Southern Oscillation

Astier, Nicolas ; Plu, Matthieu ; Claud, Chantal

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The link between El Niño Southern Oscillation (ENSO) and tropical cyclone activity over the Southwest Indian Ocean [(0°-30°S) × (48°-90°E)] is revisited. Based on the records for 1981-2013, we show that cyclonic activity decreases dramatically during strong ENSO events: only a few cases are observed during the January-March period. This pattern is attributed to changes in large-scale thermodynamic parameters. Although El Niño is correlated with an increase in tropospheric moisture and sea-surface temperatures, it is also associated with an equatorward shift of the subtropical jet. When El Niño is sufficiently strong, the latter effect may dominate the former, inhibiting tropical cyclone activity.

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