CMIP5 Projections of Two Types of El Niño and Their Related Tropical Precipitation in the 21st Century

Kang Xu, South China Sea Institute of Oceanology, Chinese Academy of Sciences, State Key Laboratory of Tropical Oceanography, Guangzhou, China, Chi-Yung Tam, The Chinese University of Hong Kong, Earth System Science (ESSC), Hong Kong, Hong Kong, Congwen Zhu, Chinese Academy of Meteorological Sciences, Institute of Climate Systems, Beijing, China and Weiqiang Wang, South China Sea Institute of Oceanology, Chinese Academy of Sciences, State Key Laboratory of Tropical Oceanography, Guangzhou 510301, China
Abstract:
Future projections of the Eastern-Pacific (EP) and Central-Pacific (CP) types of El Niño-Southern Oscillation (ENSO) in the 21st century, as well as their associated tropical precipitation variability, are investigated on the basis of the historical runs and the representative concentration pathway 8.5 (RCP8.5) simulations of 31 coupled models involved in the Coupled Model Intercomparison Project phase 5 (CMIP5). EP and CP El Niño events, as well as their related tropical circulation anomalies, are identified based on the empirical orthogonal function (EOF) analysis of the tropical Pacific sea surface temperature (SST). Results from the CMIP5 historical runs indicate that the CMIP5 models are more capable of simulating the EP El Niño (100%) than that of the CP El Niño (17 out of 31). As revealed by the best climate models for simulating both these two types of El Niño, the EP El Niño intensity become significantly weaker while the CP El Niño do not account for the more robust changes in the future climate, and there also exists no consensus on how the relative frequency of CP to EP El Niño may change under global warming. However, robust projected changes on the EP and CP El Niño-driven tropical precipitation variability are primarily determined by the El Niño types, following wet-get-wetter patterns. Results also demonstrate that the projected precipitation changes related to two types of El Niño exhibit strong connections to tropical circulation anomalies. Under warmer background climate, the remarkable projected changes of the tropical precipitation for EP El Niño events are primarily depended on the enhanced basic-state precipitation over the equatorial Pacific via the weakening climatology Walker circulation, leading to a significant increase (decrease) in the precipitation over the tropical eastern and central (central-to-western) Pacific, whereas those associated with CP El Niño may be strongly attributed to the strengthening local Hadley cell, resulting in more suppressed (enhanced) precipitation over the equatorial (subtropical) eastern Pacific.
Back to: El Niño–Southern Oscillation (ENSO) Diversity in a Changing Climate III Posters