Transcript ENSO FLAVORS - Ohio State University

Christian Feliciano
The Ohio State University
Atmospheric Science
Overview
 EP and CP El Nino
 First Paper
 ENSO Flavors
 Frequency of each flavor.
 Second Paper
 Natural variability
 Future Research
 Questions
Eastern Pacific ENSO….
 Typical El Nino
Pattern
 Centered over
the eastern
Pacific
 Sea surface
anomalies in the
Nino 3.4 region.
(+0.5°C)
 5°S-5°N and 120-
170°W
Kao & Yu 2007
Central Pacific El Nino…
 Newly recognize
 Centered near the
International Date
Line
 Unique global
impacts and global
warming trends
 Increase d frequency
of Central Pacific El
Nino?
Kao & Yu 2007
EP vs. CP ENSO
Examples of the eastern-Pacific and central-Pacific types of ENSO: (a) SST anomalies
averaged from November 1997 to January 1998 of the 1997/98 El Nino event and (b) SST
anomalies averaged from November 1977 to January 1978 of the 1977/78 El Nino event
Nathaniel C. Johnson
International Pacific Research Center, School of Ocean and Earth
Science and Technology, University of Hawaii Manoa, Honolulu,
Hawaii
Data and Methodology
 Self-organizing map analysis (SOM)
 Grouping tool
 ENSO flavors defined by SOM SST anomaly patterns in the
equatorial Pacific
 September–February mean SST data from 1950 through
2011 derived from the Extended Reconstructed Sea Surface
Temperature Dataset
 Pacific region between 120°E and 50°W and between 25°S
and 25°N
SOM Patterns
Johnson 2012
Johnson 2012
Frequency
Johnson 2012
Results/Conclusion
 Pattern 6, 7, and 8 represent CP
ENSO
 Pattern 9 represents EP ENSO
(also the strongest El Nino
events)
 A transition from La Nina–like
patterns with weak or negative
SST anomalies in the western
Pacific warm pool (1 and 2) to La
Nina–like patterns with positive
SST anomalies in the western
Pacific warm pool (3 and 4) 
Drought?
 Natural variability or global
warming?
Matthew Newman
Sang-Ik Shin
Michael A. Alexander
Geophysical Research Journal 2007
Background
 Based off of the paper “The Optimal Growth of
Tropical Seas Surface Temperature Anomalies” by
Cecile Penland and Prashant D. Sardeshmukh
 Used many of the same techniques
 SST precursor patterns
 Correlate optimal SST patters to observed ENSO
events
Findings
Motivation
 1)Dynamics that lead to various ENSO flavors
 2) Does the recent increase in CP ENSO a result of
decadal change
 3)Does the recent increase in CP ENSO a result of
anthropogenic climate change
Data and Methodology
 Linear Inverse Modeling (LIM)
 3‐month running mean anomalies of observed SST,
thermocline depth(depth of 20°C isotherm) and
surface zonal wind stress in the Tropics (30°S–30°N)
during 1959–2000.
 multivariate, “patterns‐based”, red noise approach to
42 years of observed tropical SST, thermocline depth,
and zonal wind stress seasonal anomalies
ENSO Dynamics
Newman 2011
1) Tropical SST growth factor for the EP pattern is almost 4 times greater than for
the CP pattern
2) CP ENSO has a cold phase
Results/Conclusion
 EP ENSO events form as a result of the discharge-recharge theory
lead to stronger El Nino
 CP ENSO events have no thermocline-surface interactions. SST
anomalies are advected into the region  lead to longer lasting weaker
El Nino
 Natural random variations can account for the observed variability of
Central Pacific (CP) and Eastern Pacific (EP) ENSO events
 Increasing trend in the frequency of CP El Nino events may be
indistinguishable from natural variability
 Data set to small
Future Research
 Global impacts of CP ENSO
 Similar to EP ENSO?
 Stronger/Weaker?
 Better understanding of the variability and dynamics
of CP/EP ENSO flavors/events
 Will the warming trend in the west Pacific for La Nina
events continue?
 What are the global impacts
Questions??
References
 http://www.ncdc.noaa.gov/teleconnections/enso/indicators/sst.php
 Hsun-Ying Kao and Jin-Yi Yu, 2009: Contrasting Eastern-Pacific and CentralPacific Types of ENSO. J. Climate, 22, 615–632. doi:
http://dx.doi.org/10.1175/2008JCLI2309.1
 Nathaniel C. Johnson, 2013: How Many ENSO Flavors Can We Distinguish?*. J.
Climate, 26, 4816–4827. doi: http://dx.doi.org/10.1175/JCLI-D-12-00649.1
 Michael A. Alexander, Ludmila Matrosova, Cécile Penland, James D. Scott, and
Ping Chang, 2008: Forecasting Pacific SSTs: Linear Inverse Model Predictions
of the PDO. J. Climate, 21, 385–402. doi:
http://dx.doi.org/10.1175/2007JCLI1849.1
 Newman, M., S.-I. Shin, and M. A. Alexander (2011), Natural variation in ENSO
flavors, Geophys. Res. Lett., 38, L14705, doi:10.1029/2011GL047658