On the time evolution of ENSO and its teleconnections in an ensemble view – a new perspective

Abstract

Abstract. The changes in the El Niño–Southern Oscillation (ENSO) phenomenon and its precipitation-related teleconnections over the Globe under climate change are investigated in the Community Earth System Model's Large Ensemble from 1950 to 2100. For the investigation, a recently developed ensemble-based method, the snapshot empirical orthogonal function (SEOF) analysis is used. The instantaneous ENSO pattern is defined as the leading mode of the SEOF analysis carried out at a given time instant over the ensemble. The corresponding principal components (PC1s) characterize the ENSO phases. We find that the largest amplitude changes in the variability of the sea surface temperature fields occur in the June–July–August–September (JJAS) season, in the Niño3–Niño3.4 region and in the eastern part of the Pacific Ocean, however, the increase is also considerable along the Equator in December–January–February (DJF). The Niño3 amplitude shows also an increase of about 20 % and 10 % in JJAS and DJF, respectively. The strength of the precipitation-related teleconnections of the ENSO is found to be non-stationary, as well. For example, the anti-correlation with precipitation in Australia in JJAS and the positive correlation in Central and North Africa in DJF are predicted to be more pronounced by the end of the 21th century. Half-year-lagged correlations, aiming to predict precipitation conditions from ENSO phases, are also studied. The Australian, Indonesian precipitation and that of the eastern part of Africa in both JJAS and DJF seem to be well predictable based on ENSO phase, while the South Indian precipitation is in relation with the half-year previous ENSO phase only in DJF. The strength of these connections increases, especially from the African region to the Arabian Peninsula.

The Theory of Parallel Climate Realizations

“…Finally, we mention that the SEOF method can also be used as a refined characterization of ENSO. Preliminary results [110] suggest that the influence of the ENSO on the Indian Monsoon increases in the 21st century: the anticorrelation becomes stronger, resulting in wetter summers in India in El Niño years. The Arctic and the tropics exhibit considerable connections with each other, therefore, studying ENSO and AO as a coupled system could be an interesting direction of future research.…”