Relative Contributions of Mean-State Shifts and ENSO-Driven Variability to Precipitation Changes in a Warming Climate

• Published in: Journal of climate 2015-12, Vol.28 (24), p.9997-10013
• Main Authors: Bonfils, Céline J. W., Santer, Benjamin D., Phillips, Thomas J., Marvel, Kate, Leung, L. Ruby, Doutriaux, Charles, Capotondi, Antonietta
• Format: Article
• Language: English
• Subjects: Anomalies; Climate change; Climate models; Datasets; El Nino; El Nino phenomena; El Nino-Southern Oscillation event; El Niño-Southern Oscillation; ENSO; Extreme weather; General circulation models; GHG; Global climate models; Global warming; greenhouse-gas; Hydroclimate; Laboratories; Meteorology; Meteorology And Climatology; Modeling; Precipitation; Precipitation variability; R&D; Rainfall; Rainfall anomalies; Rainfall forecasting; Research & development; Sea surface; sea-surface temperature; Simulation; Southern Oscillation; Spatial models; SST; teleconnection; Teleconnection patterns; Teleconnections; Temporal variability; Temporal variations; Time series; Tropical regions; Variability
• ISSN: 0894-8755; 1520-0442
• DOI: 10.1175/JCLI-D-15-0341.1

El Niño–Southern Oscillation (ENSO) is an important driver of regional hydroclimate variability through far-reaching teleconnections. This study uses simulations performed with coupled general circulation models (CGCMs) to investigate how regional precipitation in the twenty-first century may be affected by changes in both ENSO-driven precipitation variability and slowly evolving mean rainfall. First, a dominant, time-invariant pattern of canonical ENSO variability (cENSO) is identified in observed SST data. Next, the fidelity with which 33 state-of-the-art CGCMs represent the spatial structure and temporal variability of this pattern (as well as its associated precipitation responses) is evaluated in simulations of twentieth-century climate change. Possible changes in both the temporal variability of this pattern and its associated precipitation teleconnections are investigated in twenty-first-century climate projections. Models with better representation of the observed structure of the cENSO pattern produce winter rainfall teleconnection patterns that are in better accord with twentieth-century observations and more stationary during the twenty-first century. Finally, the model-predicted twenty-first-century rainfall response to cENSO is decomposed into the sum of three terms: 1) the twenty-first-century change in the mean state of precipitation, 2) the historical precipitation response to the cENSO pattern, and 3) a future enhancement in the rainfall response to cENSO, which amplifies rainfall extremes. By examining the three terms jointly, this conceptual framework allows the identification of regions likely to experience future rainfall anomalies that are without precedent in the current climate.