ENSO modulation of tropical Indian Ocean subseasonal variability. Issue 24 (30th December 2016) - Jung, Eunsil
Abstract: In this study, we use 30 years of retrospective climate model forecasts and observational estimates to show that El Niño/Southern Oscillation (ENSO) affects the amplitude of subseasonal variability of sea surface temperature (SST) in the southwest Indian Ocean, an important Tropical Intraseasonal Oscillation (TISO) onset region. The analysis shows that deeper background mixed‐layer depths and warmer upper ocean conditions during El Niño reduce the amplitude of the subseasonal SST variability over Seychelles‐Chagos Thermocline Ridge (SCTR), which may reduce SST‐wind coupling and the amplitude of TISO variability. The opposite holds for La Niña where the shallower mixed‐layer depth enhances SST variability over SCTR, which may increase SST‐wind coupling and the amplitude of TISO variability. Key Points: Amplitude of subseasonal SST variability over the Seychelles‐Chagos Thermocline Ridge (SCTR) is highly correlated with ENSO During El Niño, SST is warmer and mixed layer is deeper than normal over the SCTR The deeper mixed layers with warmer upper ocean conditions reduce the subseasonal SSTA variability over the SCTR