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Remarkable interannual variability in the thermocline depth in the southern tropical Indian Ocean (STIO) is analyzed using reanalysis data during 1980–2017. Previous studies have shown that the El Niño‐Southern Oscillation (ENSO) has a significant relationship with thermocline depth anomalies in this region. We find that both the eastern‐Pacific (EP) and central‐Pacific (CP) ENSO have important impacts on the STIO thermocline variation. The positive and negative phases of thermocline anomalies in the STIO are induced by asymmetric forcings from the two phases of ENSO. EP‐El Niño and CP‐La Niña events tend to induce larger thermocline depth anomalies in the STIO. Equatorial westerly and STIO anticyclonic winds during EP‐El Niño events can induce downwelling Rossby waves that extend far toward the western Indian Ocean, which dominates the westward propagation of thermocline anomalies, while upwelling Rossby waves during CP‐La Niña events cannot extend that far west. Plain Language Summary: Despite more researches mentioned about the global warming slowdown, the extreme events like the El Niño‐South Oscillation (ENSO) happen more frequently in the real world. Previous studies proved that the ocean thermocline depth in the southern tropical Indian Ocean (STIO) is influenced by different ENSO events (El Niño and La Niña), and the ENSO events have been divided as the eastern‐Pacific (EP) and central‐Pacific (CP) El Niño/La Niña based on different locations of the maximum sea surface temperature anomalies centers during the past decades. In this study, we present the relationships between the STIO thermocline depth and EP/CP El Niño/La Niña in this complex circumstance. We find that forcings from El Niño and La Niña are asymmetric, and the EP‐El Niño and CP‐La Niña events tend to induce larger thermocline variations. Considering these two different ENSO events, as mentioned above, happen more frequently, the variation of the STIO thermocline might be much greater in the future. Key Points: Both EP and CP ENSO events have important impacts on the thermocline variability in the STIOForcings from El Niño and La Niña events are asymmetric with the EP‐El Niño (CP‐La Niña) inducing a greater deepening (shoaling) thermoclineEP‐El Niño events induce Rossby waves extending far toward the western Indian Ocean, which induced by CP‐La Niña cannot extend far west [ABSTRACT FROM AUTHOR]

The article focuses on a research on Indian Ocean for monsoon prediction by Research Moored Array for African- Asian-Australian Monsoon Analysis and Prediction (RAMA). A new moored buoy array in the historically data-sparce Indian Ocean provides measurements to advance monsoon research and forecasting. Seasonal heating and cooling of the land in the Indian Ocean sets the stage for dramatic monsoon wind reversals and intense Seasonal rains over the Indian subcontinent, Southeast Asia, East Africa and Australia. The array complements other elements of the recently designed Indian Ocean Observing System (IndOOS) which represents an Indian Ocean contribution to RAMA.