A change in the relation between the Subtropical Indian Ocean Dipole and the South Atlantic Ocean Dipole indices in the past four decades

• Main Authors: Yu, Lejiang, Zhong, Shiyuan, Vihma, Timo, Sui, Cuijuan, Sun, Bo
• Format: Text
• Language: English
• Published: 2022
• Subjects: Indian; South Atlantic Ocean
• Online Access: https://doi.org/10.5194/acp-2022-562; https://acp.copernicus.org/preprints/acp-2022-562/

We utilized the global atmospheric reanalysis (ERA5) and reconstructed sea surface temperature (SST) data from 1979 through 2020 to examine the stability of the relationship between the SST oscillations in the southern Indian and the Atlantic Oceans described by the Subtropical Indian Ocean Dipole (SIOD) and the South Atlantic Ocean Dipole (SAOD) indices. We note a significant positive correlation between the two indices prior to the year 2000 but practically no correlation afterwards. We show that in the two decades prior to 2000, a positive phase of SAOD is associated with more convective activities over the subtropical southern Atlantic Ocean and eastern Brazil, which trigger a stronger upper-atmosphere wavetrain, and further produces stronger southern subtropical highs and surface anti-cyclonic circulations and therefore a stronger correlation between the two indices. The situation is reversed after 2000. Our results are potentially applicable for predictions of precipitation in southern Africa and South America.