1185 / 2024-09-20 16:19:24

Linear inverse models as a tool for understanding Indo-Pacific tropical SST variability

Indian Ocean

The impacts of tropical interbasin interaction (TBI) on the characteristics and predictability of sea surface temperature (SST) in the Indo-Pacific region are assessed using a linear inverse modeling (LIM) framework that focuses on SST and sea surface height anomalies in the tropics. The TBI pathways between these regions are successfully isolated in stochastically-forced simulations that modify the off-diagonal elements of the linear operators. The removal of TBI leads to a substantial increase in the amplitude of El Niño-Southern Oscillation (ENSO) and related variability in the Indo-Pacific. Partial decoupling experiments show that Pacific-Indian interaction is the dominant contributor, while Pacific-Atlantic and Atlantic-Indian interactions play a more minor role. A series of retrospective forecast experiments demonstrates that decoupling results in a significant decrease in ENSO prediction skill, particularly for longer lead times. The relative contributions of individual pathways to forecast skill are consistent with the results from the stochastically-forced experiments. Additional forecast experiments with partial initialization over specific basins show qualitatively similar results, though several differences arise due to the distinct representations of each TBI pathway.