The Combined Influence of ENSO and IOD over South America climate during Austral Spring

LUCIANO ANDRIAN; MARISOL OSMAN; CAROLINA VERA

Conferencia; 13th International Conference on Southern Hemisphere Meteorology and Oceanography; 2022

In austral spring, El Niño events are associated with positive temperature anomalies in central and northern South America (SA), and with positive precipitation anomalies in southeastern SA and negative in the northern SA. Opposite conditions tend to prevail during La Niña. While these impacts are expected during different El Niño-Southern Oscillation (ENSO) events, they do not necessarily occur during every episode. In addition, these impacts can also be altered by competing influences from other sources of climate variability, like the Indian Ocean Dipole (IOD). The IOD, which maximizes in the austral spring, also influences SA and is characterized by positive precipitation anomalies in the La Plata Basin and negative in central Brazil during its positive phase. In the extratropical SA region, ENSO and IOD exert their influence through very similar Rossby wave trains (referred to as the Pacific-South American (PSA) pattern in the case of ENSO), and the extent by which ENSO impacts in SA can be affected due to the joint occurrence of the IOD has received very little attention.To address this issue, we study the combined influence of ENSO and IOD on the climate of SA. We focus on austral spring during which both the ENSO and IOD impacts are largest. Climate data for the last 100 years are used to gain robustness in the analysis and we use composites and conditional composites to assess the role of both climate drivers. The results of this study will underpin the climate monitoring capabilities of the Argentina National Weather Service and the Regional Climate Center for Southern South America.