Antarctic Oscillation: Its Influence on the Interannual Variability of Precipitation in the Indian Monsoon Region

Abstract

This study investigated the influence of the Antarctic Oscillation (AAO) on the interannual variability of precipitation in the Indian monsoon region, aiming to address discrepancies in the existing literature. The degree of correlation between the AAO and moisture transport from the main oceanic sources supplying moisture to India, as well as precipitation over the region, was assessed using Pearson and partial correlation coefficients. The latter was employed to account for the potential confounding influence of the El Niño-Southern Oscillation (ENSO), the dominant mode of climatic variability. Five datasets were used: moisture sinks derived from the FLEXPART model driven by ERA-Interim data (1980-2012), and precipitation data (1984-2016) from two surface rain gauge datasets (IITM-IMR and IMD4), ERA5 reanalysis, and PERSIANN-CDR. In addition, spatial patterns of climate teleconnections associated with the AAO were analyzed using a composite approach. Seasonal time series were constructed under two analytical frameworks: the first (scenario A1) was based on patterns linked to seasonal variations in solar radiation between hemispheres due to Earth’s orbital movement around the Sun, while the second (scenario A2) focused on patterns associated with the strengthening and weakening of the Antarctic polar vortex, considering the specific climatic characteristics of India. Among the key findings, scenario A2 yielded improved results compared to scenario A1. The strongest correlation emerged over the Peninsular region, where the AAO showed a significant in-phase relationship with precipitation during October, November, and December (OND), and an out-of-phase relationship with precipitation during January-February (JF), relative to the OND period. Another notable result was found for the Northwestern region, where a positive relationship was identified between the AAO during the June-September (JJAS) period and precipitation during the subsequent OND season. These findings align with the “coupled ocean-atmosphere bridge” mechanism, which involves anomalies in the high-pressure system over the Indian Ocean and its interaction with key components of the Indian monsoon system.