The tropical Pacific climate state response to both the 21st-century greenhouse gas forcing and orbital forcing on a glacial–interglacial timescale tends to resemble either an El Niño- or La Niña-like pattern. This study reveals that so long as an El Niño- or La Niña-like change in the tropical climate state occurs, changes in two important negative feedback components of the El Niño-Southern Oscillation (ENSO) system, dynamical damping by mean thermal advection (MA) and thermo-dynamical damping (TD), largely offset each other. For example, under the El Niño-like condition, weaker trade winds due to a relaxed zonal sea surface temperature (SST) gradient reduce the mean zonal and meridional currents in the equatorial Pacific oceanic mixed layer, causing a reduction in MA, while wider expansion and enhanced activity of climatological convective clouds due to a warmer ocean surface intensifies negative SST-cloud-shortwave feedback. As a result, a change in ENSO activity in changing climate is mainly ruled out not by the change in negative feedback effect, but by the change in positive feedback effect.
Bibliographical noteFunding Information:
information National Research Foundation of Korea, Grant/Award Number: NRF-2017K1A3A7A03087790, NRF-2018R1A5A1024958This research was supported by the Basic Science Research Programme through the National Research Foundation of Korea (NRF-2017K1A3A7A03087790, NRF-2018R1A5A1024958). We acknowledge the World Climate Research Programme's Working Group on Coupled Modelling, which is responsible for CMIP, and we thank the climate modelling groups (listed in Table of this paper) for producing and making available their model output. For CMIP, the U.S. Department of Energy?s Programme for Climate Model Diagnosis and Intercomparison provides coordinating support and leads the development of the software infrastructure in partnership with the Global Organization for Earth System Science Portals.
© 2019 Royal Meteorological Society
All Science Journal Classification (ASJC) codes
- Atmospheric Science