Diversity of ENSO Events Unified by Convective Threshold Sea Surface Temperature: A Nonlinear ENSO Index

Author(s): Williams, IN; Patricola, CM | Abstract: ©2018. American Geophysical Union. All Rights Reserved. We show that the well-known failure of any single index to capture the diversity and extremes of El Nino-Southern Oscillation (ENSO) results from the inability of existing indices to uniquely characterize the average longitude of deep convection in the Walker Circulation. We present a simple sea surface temperature (SST)-based index of this longitude that compactly characterizes the different spatial patterns, or flavors of observed and projected ENSO events. It recovers the familiar global responses of temperature, precipitation, and tropical cyclones to ENSO and identifies historical extreme El Nino events. Despite its simplicity, the new longitude index describes the nonlinear relationship between the first two principal components of SST, and unlike previous indices, accounts for background SST changes associated with the seasonal cycle and climate change. The index reveals that extreme El Nino, El Nino Modoki, and La Nina events are projected to become more frequent in the future at the expense of neutral ENSO conditions.

[1]  R. Saravanan,et al.  Degree of simulated suppression of Atlantic tropical cyclones modulated by flavour of El Niño , 2016 .

[2]  A. Barnston,et al.  Observing and Predicting the 2015/16 El Niño , 2017 .

[3]  A. E. Gill.  Some simple solutions for heat‐induced tropical circulation , 1980 .

[4]  E. Guilyardi,et al.  ENSO representation in climate models: from CMIP3 to CMIP5 , 2013, Climate Dynamics.

[5]  Sarah M. Kang,et al.  Global energetics and local physics as drivers of past, present and future monsoons , 2018, Nature Geoscience.

[6]  A. Timmermann,et al.  Increasing frequency of extreme El Niño events due to greenhouse warming , 2014 .

[7]  I. Held,et al.  Modeling Tropical Convergence Based on the Moist Static Energy Budget , 1987 .

[8]  D. Vimont,et al.  Analogous Pacific and Atlantic Meridional Modes of Tropical Atmosphere-Ocean Variability* , 2004 .

[9]  S. Camargo,et al.  The Influence of ENSO Flavors on Western North Pacific Tropical Cyclone Activity , 2018, Journal of Climate.

[10]  Richard Tinker,et al.  Climate Assessment for 1999 , 2000 .

[11]  Quanliang Chen,et al.  Impacts of the Tropical Pacific Cold Tongue Mode on ENSO Diversity Under Global Warming , 2017 .

[12]  Tapio Schneider,et al.  Migrations and dynamics of the intertropical convergence zone , 2014, Nature.

[13]  G. Manucharyan,et al.  Robust ENSO across a Wide Range of Climates , 2014 .

[14]  Eli Tziperman,et al.  Irregularity and Locking to the Seasonal Cycle in an ENSO Prediction Model as Explained by the Quasi-Periodicity Route to Chaos , 1995 .

[15]  C. Deser,et al.  How Well Do We Know ENSO’s Climate Impacts over North America, and How Do We Evaluate Models Accordingly? , 2018, Journal of Climate.

[16]  N. Johnson,et al.  The impact of eastern equatorial Pacific convection on the diversity of boreal winter El Niño teleconnection patterns , 2016, Climate Dynamics.

[17]  Kevin E. Trenberth,et al.  Indices of El Niño Evolution , 2001 .

[18]  Dake Chen,et al.  ENSO in the CMIP5 Simulations: Life Cycles, Diversity, and Responses to Climate Change , 2017 .

[19]  Alex Hall,et al.  Increasing precipitation volatility in twenty-first-century California , 2018, Nature Climate Change.

[20]  R. Neale,et al.  The Impact of Convection on ENSO: From a Delayed Oscillator to a Series of Events , 2008 .

[21]  Swadhin K. Behera,et al.  El Niño Modoki and its possible teleconnection , 2007 .

[22]  R. Pierrehumbert,et al.  Global warming, convective threshold and false thermostats , 2009 .

[23]  M. Huber,et al.  El Niño in the Eocene greenhouse recorded by fossil bivalves and wood from Antarctica , 2011 .

[24]  Elizabeth C. Kent,et al.  Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century , 2003 .

[25]  Christopher S. Bretherton,et al.  Modeling Tropical Precipitation in a Single Column , 2000 .

[26]  E. Guilyardi,et al.  Understanding ENSO Diversity , 2015 .

[27]  P. Webster,et al.  Evolution and modulation of tropical heating from the last glacial maximum through the twenty-first century , 2012, Climate Dynamics.

[28]  Shang-Ping Xie,et al.  Intermodel Uncertainty in ENSO Amplitude Change Tied to Pacific Ocean Warming Pattern , 2016 .

[29]  J. Horel.  On the Annual Cycle of the Tropical Pacific Atmosphere and Ocean , 1982 .

[30]  R. Pierrehumbert,et al.  Observational evidence against strongly stabilizing tropical cloud feedbacks , 2017 .

[31]  M. Hoerling,et al.  Atmospheric Response Patterns Associated with Tropical Forcing , 2002 .

[32]  Dietmar Dommenget,et al.  Analysis of the non-linearity in the pattern and time evolution of El Niño southern oscillation , 2013, Climate Dynamics.

[33]  Jin‐Yi Yu,et al.  Why were the 2015/2016 and 1997/1998 extreme El Niños different? , 2017 .

[34]  S. Xie,et al.  Changes in the sea surface temperature threshold for tropical convection , 2010 .

[35]  ENSO regimes: Reinterpreting the canonical and Modoki El Niño , 2011 .

[36]  M. Huber,et al.  Eocene El Niño: Evidence for Robust Tropical Dynamics in the "Hothouse" , 2003, Science.

[37]  P. deMenocal,et al.  The Pliocene Paradox (Mechanisms for a Permanent El Niño) , 2006, Science.

[38]  Thomas M. Smith,et al.  Extended Reconstructed Sea Surface Temperature, Version 5 (ERSSTv5): Upgrades, Validations, and Intercomparisons , 2017 .

[39]  Arun Kumar,et al.  Winter 2015/16 Atmospheric and Precipitation Anomalies over North America: El Niño Response and the Role of Noise , 2018 .

[40]  C. Deser,et al.  Twentieth century tropical sea surface temperature trends revisited , 2010 .

[41]  K.,et al.  The Community Earth System Model (CESM) large ensemble project: a community resource for studying climate change in the presence of internal climate variability , 2015 .

[42]  D. E. Harrison,et al.  El Niño Impacts on Seasonal U.S. Atmospheric Circulation, Temperature, and Precipitation Anomalies: The OLR-Event Perspective* , 2013 .

[43]  M. Kanamitsu,et al.  NCEP–DOE AMIP-II Reanalysis (R-2) , 2002 .

[44]  Agus Santoso,et al.  Increased frequency of extreme La Niña events under greenhouse warming , 2015 .

[45]  C. J. Neumann,et al.  The International Best Track Archive for Climate Stewardship (IBTrACS): unifying tropical cyclone data. , 2010 .

[46]  Kevin E. Trenberth,et al.  The Definition of El Niño. , 1997 .

[47]  Anthony C. Hirst,et al.  Interannual variability in a tropical atmosphere−ocean model: influence of the basic state, ocean geometry and nonlinearity , 1989 .

[48]  D. E. Harrison,et al.  Global Seasonal Precipitation Anomalies Robustly Associated with El Niño and La Niña Events—An OLR Perspective*,+ , 2015 .

[49]  M. Huber,et al.  Evidence for active El Nino Southern Oscillation variability in the Late Miocene greenhouse climate , 2010 .

[50]  Neville Nicholls,et al.  Relationships between the Maritime Continent Heat Source and the El Niño–Southern Oscillation Phenomenon , 2003 .

[51]  Bin Wang,et al.  Interactions between the Seasonal Cycle and El Niño-Southern Oscillation in an Intermediate Coupled Ocean-Atmosphere Model , 1995 .

[52]  Max J. Suarez,et al.  A Delayed Action Oscillator for ENSO , 1988 .

[53]  M. Cane,et al.  A Model El Niñ–Southern Oscillation , 1987 .

[54]  B. Kirtman,et al.  El Niño in a changing climate , 2009, Nature.

[55]  A. Wittenberg,et al.  On the Fragile Relationship Between El Niño and California Rainfall , 2017 .