| Summary: | We utilized the global atmospheric reanalysisERA5 and reconstructed sea surface temperature(SST) data from1979 through2020 to examine the stability of the relationship between the SST oscillations in the southern Indian Ocean and the Atlantic Ocean, as described by the Subtropical Indian Ocean Dipole(SIOD) and South Atlantic Ocean Dipole(SAOD) indices, respectively. We note a significant positive correlation between the two indices prior to the year2000 but practically no correlation afterwards. We show that in the two decades prior to2000, a positive phase of the SAOD is associated with more convective activities over the subtropical southern Atlantic Ocean and eastern Brazil, which trigger a stronger upper-atmosphere wavetrain. This produces stronger southern subtropical highs and surface anti-cyclonic circulations and therefore a stronger correlation between the two indices. The situation is reversed after2000. Our results are potentially applicable to predictions of precipitation in southern Africa and South America.
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