Ensemble Oceanic NINO Index (ENS ONI)
Figure 1. November-February 1877-78 ERSSTv5 Tropical Pacific sea surface temperature anomalies
MAJOR UPDATES TO THE ENSEMBLE OCEANIC NINO INDEX (ENS ONI)
June 2019: HADSST4 was added to the analysis, resulting in a slight increase in amplitude of most pre-1950 ENSO events due to better constraint of quality control procedures. The standard deviation of available SST datasets used in the ENS ONI is now also provided.
July 2019: ERA-5 was added to the analysis & interpolated to a 1x1 degree grid to make it more comparable to other datasets used in the ENS ONI. Its addition resulted in little notable change in the ENS ONI after 1964. The ENS ONI quality control procedure was reevaluated for the 1877-78 El Nino, resulting in more realistic amplitude evolution during the growth phase of this "Super" El Nino in 1877. Changes in the 1877-78 El Nino also implicated nearby portions of the record, leading to an extremely modest modification of other ONI values from 1865 to 1890.
July 2019: ERA-5 was added to the analysis & interpolated to a 1x1 degree grid to make it more comparable to other datasets used in the ENS ONI. Its addition resulted in little notable change in the ENS ONI after 1964. The ENS ONI quality control procedure was reevaluated for the 1877-78 El Nino, resulting in more realistic amplitude evolution during the growth phase of this "Super" El Nino in 1877. Changes in the 1877-78 El Nino also implicated nearby portions of the record, leading to an extremely modest modification of other ONI values from 1865 to 1890.
Introduction
The Ensemble Oceanic NINO Index (ENS-ONI) is one of the longest running, real-time, observation-based ENSO index that has been developed to date spanning from the mid 19th century to the present. The ENS ONI closely follows the methodology of the Climate Prediction Center (CPC), and is computed by using seasonally averaged sea surface temperature (SST) anomalies in the NINO 3.4 region (5S-5N, 120-170W) over the Equatorial Pacific as defined by Barnston, Chelliah, and Goldenberg (1997). Following this publication, the NINO 3.4 index became one of the most popular ENSO indices at the turn of the 21st century. The exceptional combined intensity and longevity of the 2014-16 multi-year "Super" El Nino event in the context of modern single-year modern "Super" El Nino events in 1972-73, 1982-83, & 1997-98 spurred the creation of the ENS ONI. The ENS ONI attempts to provide as long and reliable of an instrumentally-based ENSO record as possible while maintaining simplicity in its construction and being available for real-time scrutiny. While the quality and quantity of data platforms and spatiotemporal coverage is relatively less reliable, less numerous, and more sparse respectively, the number of ENSO event samples under the ENS ONI is more than double the "reliable" record (1950-present).
Figure 2. NINO SST regions
Data
The ENS ONI utilizes World Meteorological Organization (WMO) 30 year climatological base periods that are updated every 5 years to account for significant changes and inhomogeneities in the background climatic and observational mean state in the last few centuries. Raw data rounded to the nearest 0.01C was attained and datasets such as Kaplan's Extended SST Version 2, were converted from anomalies to raw data using their respective climatologies. A confidence interval with a z-score of nearly 6 sigma is utilized to filter out datasets with potentially "spurious" data each month beginning in 1870 and monthly new averages are computed from the remaining data. This procedure increases the stability, robustness, and reliability of the ENS ONI, provides a more realistic depiction of ENSO events and increases their amplitude slightly, especially before 1950 when there's more uncertainty and spread amongst available datasets, in addition to less data. From the nearly 30,000 NINO 3.4 monthly SST values from each individual dataset that are used to construct the ENS ONI, the aforementioned quality control methodology filters out ~15% of the data.
Although this index exhibits very robust correlations with the Bivariate ENSO Timeseries (BEST), Multivariate ENSO Index (MEI), Extended Multivariate ENSO Index (MEI.ext), this product is preliminary and should be used with caution. The following 26 sea surface temperature, satellite, and reanalysis datasets and their respective contributions to this index were analyzed in the creation of the ENS ONI:
COBE SST 2 (1850-2018)
HADSST4 (1850-2018)
NOAAs 20th Century Reanalysis Version 2c (1854-2014)
ERSST Version 5 (1854-Present)
ERSST Version 4 (1854-Present)
Kaplan's Extended SST Version 2 (1856-Present)
HADISST (1870-Present)
NOAAs 20th Century Reanalysis Version 2 (1871-2012)
IOCADSv3 (1878-Present)
ERSST Version 3b (1880-Present)
COBE SST (1891-Present)
ERA-20CM (1900-2010)
ERA-20C (1900-2010)
CERA-20C (1901-2010)
NCEP/NCAR Reanalysis Version 1 (1948-Present)
HADSST2 (1950-2014)
HADSST3 (1950-Present)
WHOI OA Flux Version 3 (1958-2018)
Climate Analysis Center (CAC) (now known as the CPC) SST (1970-March 2003)
NCEP CFSR (1979-2015)
NCEP DOE R2 (1979-Present)
ERA-Interim (1979-Present)
NASA MERRA (1979-2016)
OISSTv1 (1 degree) (Nov 1981-March 2003)
OISSTv2 (1 degree) (Nov 1981-Present)
Aqua/MODIS SST (1 degree) (July 2002-Present)
A time series plot for the number of datasets used at various points in the instrumental record is depicted in figure 3.
Although this index exhibits very robust correlations with the Bivariate ENSO Timeseries (BEST), Multivariate ENSO Index (MEI), Extended Multivariate ENSO Index (MEI.ext), this product is preliminary and should be used with caution. The following 26 sea surface temperature, satellite, and reanalysis datasets and their respective contributions to this index were analyzed in the creation of the ENS ONI:
COBE SST 2 (1850-2018)
HADSST4 (1850-2018)
NOAAs 20th Century Reanalysis Version 2c (1854-2014)
ERSST Version 5 (1854-Present)
ERSST Version 4 (1854-Present)
Kaplan's Extended SST Version 2 (1856-Present)
HADISST (1870-Present)
NOAAs 20th Century Reanalysis Version 2 (1871-2012)
IOCADSv3 (1878-Present)
ERSST Version 3b (1880-Present)
COBE SST (1891-Present)
ERA-20CM (1900-2010)
ERA-20C (1900-2010)
CERA-20C (1901-2010)
NCEP/NCAR Reanalysis Version 1 (1948-Present)
HADSST2 (1950-2014)
HADSST3 (1950-Present)
WHOI OA Flux Version 3 (1958-2018)
Climate Analysis Center (CAC) (now known as the CPC) SST (1970-March 2003)
NCEP CFSR (1979-2015)
NCEP DOE R2 (1979-Present)
ERA-Interim (1979-Present)
NASA MERRA (1979-2016)
OISSTv1 (1 degree) (Nov 1981-March 2003)
OISSTv2 (1 degree) (Nov 1981-Present)
Aqua/MODIS SST (1 degree) (July 2002-Present)
A time series plot for the number of datasets used at various points in the instrumental record is depicted in figure 3.
Figure 3. Number of datasets included in the ENS ONI (annually smoothed) (1850-Present).
Created using Matlab 2019a
Created using Matlab 2019a
For more information on the ENS ONI and 19th-21st century ENSO behavior see my 2017 AMS Conference Poster Presentation: "A Reanalysis of the Extended Multivariate ENSO Index (MEI.ext) and Comparison of the 1877-78 and 2015-16 El Nino Events"
Data for the ENS ONI was obtained at:
Climate Prediction Center (CPC): Monthly Atmospheric and SST Indices
ECMWF Climate Reanalysis
Global Climate Observing System (GCOS) Working Group on Surface Pressure (WG-SP)
International Research Institute for Climate and Society
Koninklijk Nederlands Meteorologisch Instituut (KNMI) Climate Explorer
Met Office Hadley Centre observation datasets
NASA Earth Observations
NCAR's Research Data Archive
NOAA's Earth System Research Laboratory
NOAA's Science Data Integration Group Live Access Server
Data for the ENS ONI was obtained at:
Climate Prediction Center (CPC): Monthly Atmospheric and SST Indices
ECMWF Climate Reanalysis
Global Climate Observing System (GCOS) Working Group on Surface Pressure (WG-SP)
International Research Institute for Climate and Society
Koninklijk Nederlands Meteorologisch Instituut (KNMI) Climate Explorer
Met Office Hadley Centre observation datasets
NASA Earth Observations
NCAR's Research Data Archive
NOAA's Earth System Research Laboratory
NOAA's Science Data Integration Group Live Access Server
Discussion and analysis
Although the ENS ONI is comprised of a multitude of datasets with disparate spatial and temporal resolutions, and only utilizes SST anomalies in a seemingly inconsequential region of the equatorial Pacific, the standard deviation amongst various available datasets appears to be somewhat reflective of global trends during the instrumental record. This very crude estimate of parametric uncertainty reflects structural uncertainties amongst available datasets and their sensitivity to data input, which occurs because most datasets in the ENS ONI are effectively not constructed the same way and many datasets include different versions of ICOADS and/or other observational sources (especially reanalysis datasets) respectively. Both are important points regarding uncertainty in the instrumental record that tend to be less frequently discussed in literature. Nonetheless, from the standard deviation of SSTs in the NINO 3.4 region, three primary periods of contention and notable disagreement emerge from the observed record, namely before the 1877-78 "Super" El Nino, and during the first and second World Wars. The period before 1877-78 and the first World War is largely explained by a lack of data with the latter data outage being associated with ships being sunk during the war. The apparent discrepancy amongst available datasets in and around World War 2 however is multi-faceted, featuring both a similar loss of potential data from ships sunk in the war in addition to paradigm shift in how SST observations were taken, with many ships switching from insulated bucket to engine room intake (ERI) measurements of SST.
These three aforementioned periods that are the source(s) of significant discrepancy in the instrumental record are highlighted in orange & labeled in figure 4 below.
These three aforementioned periods that are the source(s) of significant discrepancy in the instrumental record are highlighted in orange & labeled in figure 4 below.
Figure 4. Ensemble Oceanic Nino Index Inter-Dataset SST Deviation (annually smoothed) (1850-present)
Created using Matlab 2019a
Created using Matlab 2019a
Attempts at reconstructing ENSO using multiple datasets and the Oceanic Nino Index has been attempted before as recently as Huang et al (2016), however their analysis was strictly limited to only several SST datasets and over the period 1950-present.
Following the methodology of Jan Null, El Nino and La Nina events are further binned into Weak, Moderate, Strong, and "Super" based on their maximum tri-monthly ENS ONI peak shown below in figure 5. The following peak ONI values correspond to each ENSO category. You should note that there are slightly more "Super" El Ninos than "Super La Ninas, indicative of ENSO asymmetry attributable to "non-linear dynamical heating" (An & Jin (2003), Hayashi & Jin (2017)) and other, more efficient feedbacks in El Nino.
Weak El Nino/La Nina: < 1C
Moderate El Nino/La Nina: 1-1.5C
Strong El Nino/La Nina: 1.5-2C
"Super" El Nino/La Nina: 2C+
Weak El Nino/La Nina: < 1C
Moderate El Nino/La Nina: 1-1.5C
Strong El Nino/La Nina: 1.5-2C
"Super" El Nino/La Nina: 2C+
ENSO Event Phase and Intensity List (1865-2019)
"Super" El Nino: 1877-78, 1888-89, 1972-73, 1982-83, 1997-98, & 2015-16
Strong El Nino: 1896-97, 1902-03, 1930-31, 1940-41, 1957-58, 1965-66, 1987-88, 1991-92, & 2009-10
Moderate El Nino: 1885-86, 1899-00, 1905-06, 1911-12, 1918-19, 1923-24, 1925-26, 1939-40, 1941-42, 1963-64, 1968-69, 1986-87, 1994-95, & 2002-03
Weak El Nino: 1864-65 (?), 1865-66, 1868-69, 1876-77, 1880-81, 1884-85, 1887-88, 1895-96, 1900-01, 1904-05, 1913-14, 1914-15, 1919-20, 1929-30, 1951-52, 1953-54, 1958-59, 1969-70, 1976-77, 1977-78, 2004-05, 2006-07, 2014-15, & 2018-19
Weak La Nina: 1869-70, 1870-71, 1872-73, 1873-74, 1874-75, 1875-76, 1894-95, 1897-98, 1898-99, 1906-07, 1910-11, 1915-16, 1920-21, 1922-23, 1938-39, 1944-45, 1948-49, 1950-51, 1954-55, 1956-57, 1964-65, 1967-68, 1971-72, 1974-75, 1978, 1983-84, 1985-86, 1996-97, 2000-01, 2008-09, 2016-17, & 2017-18
Moderate La Nina: 1879-80, 1886-87, 1893-94, 1903-04, 1908-09, 1909-10, 1917-18, 1924-25, 1942-43, 1949-50, 1970-71, 1984-85, 1995-96, & 2011-12
Strong La Nina: 1889-90, 1892-93, 1955-56, 1975-76, 1998-99, 1999-00, 2007-08, 2010-11
"Super" La Nina: 1916-17, 1973-74, 1988-89
Figure 5. ENSO Event Intensity List (1865-2019)
Figure 6. ENS ONI time series (1865-2019)
Created using Matlab 2019a
Created using Matlab 2019a
Figure 7. Standardized ENS ONI time series (1865-2019)
Created using Matlab 2019a
Created using Matlab 2019a
Data for the ENS ONI are available here in Excel format:
Monthly NINO 3.4 SSTs (1850-Jun 2019)
ENS ONI monthly data (1865-Jun 2019)
ENS ONI tri-monthly data (1865-Jun 2019)
ENS ONI standardized tri-monthly data (1865-Jun 2019)
ENS ONI Monthly Inter-Dataset SST Standard Deviation (1851-Jun 2019)
The following ENS ONI table (also linked above) uses a modified version of the Trenberth and Hoar (1997) definition of ENSO, wherein NINO 3.4 region SST anomalies must exceed +/-0.4C for 6 successive tri-monthly periods to be classified as El Nino or La Nina event. Here, the threshold is lowered slightly to 0.3C for 6 successive tri-monthlies mainly to identify early-mid 20th century ENSO events that may have barely missed the Trenberth & Hoar or CPC thresholds due to excessive, unrealistic damping of the ENS ONI that may still be present even after quality control. El Ninos are denoted in red, La Ninas in Blue.
Monthly NINO 3.4 SSTs (1850-Jun 2019)
ENS ONI monthly data (1865-Jun 2019)
ENS ONI tri-monthly data (1865-Jun 2019)
ENS ONI standardized tri-monthly data (1865-Jun 2019)
ENS ONI Monthly Inter-Dataset SST Standard Deviation (1851-Jun 2019)
The following ENS ONI table (also linked above) uses a modified version of the Trenberth and Hoar (1997) definition of ENSO, wherein NINO 3.4 region SST anomalies must exceed +/-0.4C for 6 successive tri-monthly periods to be classified as El Nino or La Nina event. Here, the threshold is lowered slightly to 0.3C for 6 successive tri-monthlies mainly to identify early-mid 20th century ENSO events that may have barely missed the Trenberth & Hoar or CPC thresholds due to excessive, unrealistic damping of the ENS ONI that may still be present even after quality control. El Ninos are denoted in red, La Ninas in Blue.
Figures 8-22. ENS ONI tables (by decade, except for 2015-2019).
Acknowledgements
I want to provide a special thanks to my peers at UNC-Charlotte, my advisor Dr Brian Magi, and Terrell Wade (@Thunderstorm381), and so many others for their support, advice, and providing me with the necessary tools and coding skill sets to conduct this project as part of my ongoing masters thesis. Special hat tip to Terrell Wade on providing some useful insight to significantly improve the efficiency of the quality control procedure used in the ENS ONI.
References
Analyses Of Global Sea Surface Temperature 1856-1991
Alexey Kaplan, Mark Cane, and Yochanan Kushnir et al - Journal Of Geophysical Research: Oceans - 1998
agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/97JC01736
An Analysis Of the 1877–78 ENSO Episode and Comparison with 1982–83
George Kiladis and Henry Diaz - Monthly Weather Review - 1986
journals.ametsoc.org/doi/pdf/10.1175/1520-0493%281986%29114%3C1035%3AAAOTEE%3E2.0.CO%3B2
An ensemble data set of sea-surface temperature change from 1850: the Met Office Hadley Centre HADSST.4.0.0.0 data set
J.J. Kennedy et al - 2019
https://www.metoffice.gov.uk/hadobs/hadsst4/HadSST4_accepted.pdf
An Improved In Situ and Satellite SST Analysis For Climate
Richard Reynolds, Nick Rayner, Thomas Smith, Diane Stokes, and Wanqiu Wang - Journal Of Climate - 2002
ftp.emc.ncep.noaa.gov/cmb/sst/papers/oiv2pap/oiv2.pdf
Aqua: an Earth-observing Satellite Mission To Examine Water and Other Climate Variables
C.l. Parkinson - Ieee Transactions on Geoscience and Remote Sensing - 2003
ieeexplore.ieee.org/abstract/document/1196036/
A Real-time Global Sea Surface Temperature Analysis
Richard Reynolds - Journal Of Climate - 1988
journals.ametsoc.org/doi/pdf/10.1175/1520-0442%281988%29001%3C0075%3AARTGSS%3E2.0.CO%3B2
A Reanalysis Of the Extended Multivariate Enso Index (MEI.ext) and Comparison Of the 1877-78 and 2015-16 El Nino Events
Webb, Eric James - 2017
ams.confex.com/ams/97Annual/webprogram/Paper317006.html
Bivariate EnSo Timeseries or the "BEST" ENSO Index
Physical Sciences Division-ESRL Team - 2018
www.esrl.noaa.gov/psd/people/cathy.smith/best/
Centennial-scale Sea Surface Temperature Analysis and Its Uncertainty
Shoji Hirahara, Masayoshi Ishii, and Yoshikazu Fukuda - Journal Of Climate - 2014
journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-12-00837.1
CERA-20C: A Coupled Reanalysis Of the Twentieth Century
Patrick Laloyaux, Eric Boisseson, and Magdalena Balmaseda et al - Journal Of Advances in Modeling Earth Systems - 2018
agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018MS001273
Cold and Warm Episodes by Season
NOAA's Climate Prediction Center - 2018
origin.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ONI_v5.php
Documentation Of a highly ENSO‐related sst region in the equatorial pacific: Research note
Anthony Bamston, Muthuvel Chelliah, and Stanley Goldenberg - Atmosphere-ocean - 1997
www.tandfonline.com/doi/pdf/10.1080/07055900.1997.9649597?needAccess=true
ECMWF Climate Reanalysis
Sarah Keeley - 2018
www.ecmwf.int/en/research/climate-reanalysis
El Niño and Climate Change
Kevin Trenberth and Timothy Hoar - Geophysical Research Letters - 1997
agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/97GL03092
El Nino and La Nina Years and Intensities
Jan Null - 2018
ggweather.com/enso/oni.htm
El Nino/Southern Oscillation behaviour since 1871 as diagnosed in an Extended Multivariate ENSO index (MEI.ext)
Klaus Wolter and Michael Timlin - International Journal Of Climatology - 2011
rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/joc.2336
Equatorial Pacific Sea Surface Temperatures
NOAA's National Centers for Environmental Information - 2018
www.ncdc.noaa.gov/teleconnections/enso/indicators/sst/
ERA-20C: An Atmospheric Reanalysis of the Twentieth Century
Paul Poli, Hans Hersbach, and Dick Dee et al- Journal Of Climate - 2016
journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-15-0556.1
ERA-20CM: a twentieth century atmospheric model ensemble
Hans Hersbach, Carole Peubey, and Adrian Simmons et al - Quarterly Journal Of the Royal Meteorological Society - 2015
rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/qj.2528
Extended Multivariate ENSO Index (MEI.ext)
Klaus Wolter - NOAA's ESRL PSD - 2018
www.esrl.noaa.gov/psd/enso/mei.ext/
Extended Reconstructed Sea Surface Temperature, Version 4 (ERSSTv4). Part I: Upgrades and Intercomparisons
Boyin Huang, Viva Banzon, and Eric Freeman et al - Journal Of Climate - 2015
journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-14-00006.1
Extended Reconstructed Sea Surface Temperature, Version 4 (ERSSTv4): Part II: Parametric and Structural Uncertainty Estimations
Wei Liu, Boyin Huang, and Peter Thorne et al - Journal Of Climate - 2015
journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-14-00007.1
Extended Reconstructed Sea Surface Temperature, Version 5 (ERSSTv5): Upgrades, Validations, Intercomparisons
Boyin Huang, Peter Thorne, and Viva Banzon et al - Journal Of Climate - 2017
journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-16-0836.1
Further Exploring and Quantifying Uncertainties for Extended Reconstructed Sea Surface Temperature (ERSST) Version 4 (V4)
Boyin Huang, Peter Thorne, and Thomas Smith et al - Journal Of Climate - 2016
journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-15-0430.1
Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century
N. Rayner, D. E. Parker, and E.B. Horton et al
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2002JD002670
Global Climate Observing System Working Group on Surface Pressure (WG-SP)
2018
www.esrl.noaa.gov/psd/gcos_wgsp/
ICOADS 3.0: a major update to the historical marine record
Eric Freeman, Scott Woodruff, and Steven Worley et al - International Journal Of Climatology - 2016
rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/joc.4775
Improved Analyses of Changes and Uncertainties in Sea Surface Temperature Measured In Situ since the Mid-Nineteenth Century: The HADSST2 Dataset
N. A. Rayner, P. Brohan, and D. E. Parker et al - Journal of Climate - 2005
hadobs.metoffice.com/hadsst2/rayner_etal_2005.pdf
Improved Global Sea Surface Temperature Analyses Using Optimum Interpolation
Richard Reynolds and Thomas Smith - Journal Of Climate - 1994
journals.ametsoc.org/doi/pdf/10.1175/1520-0442%281994%29007%3C0929%3AIGSSTA%3E2.0.CO%3B2
Improvements to NOAA's Historical Merged Land-Ocean Surface Temperature Analysis (1880-2006)
Thomas Smith, Richard Reynolds, Thomas Peterson, and Jay Lawrimore - Journal Of Climate - 2008
journals.ametsoc.org/doi/pdf/10.1175/2007JCLI2100.1
Notes and Correspondence: Interdecadal Changes of 30-Yr SST Normals during 1871-2000
Yan Xue, Thomas M. Smith, and Richard W. Reynolds - Journal of Climate - 2002
journals.ametsoc.org/doi/pdf/10.1175/1520-0442%282003%29016%3C1601%3AICOYSN%3E2.0.CO%3B2
International Research Institute for Climate and Society
2018
iri.columbia.edu/
Koninklijk Nederlands Meterologisch Instituut (KNMI) Climate Explorer
2018
climexp.knmi.nl/start.cgi?id=someone@somewhere
Measuring the Strength of ENSO events - how does 1997/98 rank?
Klaus Wolter and Michael S. Timlin - Royal Meteorological Society - 1998
www.esrl.noaa.gov/psd/enso/mei/WT2.pdf
Met Office Hadley Centre observations datasets
2018
www.metoffice.gov.uk/hadobs/
MERRA: NASA's Modern-era Retrospective Analysis for Research and Applications
Michele Rienecker, Max Suarez, and Ronald Gelaro et al - Journal Of Climate - 2011
journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-11-00015.1
Monitoring ENSO in COADS with a Seasonally Adjusted Principal Component Index
Klaus Wolter and Michael S. Timlin - 17th Climate Diagnostics Workshop
www.esrl.noaa.gov/psd/enso/mei/WT1.pdf
Multidecade Global Flux Datasets from the Objectively Analyzed Air-sea Fluxes (OAFlux) Project: Latent and Sensible Heat Fluxes, Ocean Evaporation, and Related Surface Meteorological Variables
Lisan Yu, Xiangze Jin, and Robert A. Weller - Woods Hole Oceanographic Institute - 2008
oaflux.whoi.edu/pdfs/OAFlux_TechReport_3rd_release.pdf
Multivariate ENSO Index
Klaus Wolter - NOAA's ESRL PSD - 2018
www.esrl.noaa.gov/psd/enso/mei/
NASA Earth Observations
2018
neo.sci.gsfc.nasa.gov/view.php?datasetId=MYD28M
NCAR's Research Data Archive
2018
rda.ucar.edu/
NCEP-DOE AMIP-II Reanalysis (R-2)
Masao Kanamitsu, Wesley Ebisuzaki, and Jack Woollen et al - Bulletin Of the American Meteorological Society - 2002
journals.ametsoc.org/doi/pdf/10.1175/BAMS-83-11-1631
NOAA's Climate Prediction Center: Monthly Atmospheric & SST Indices
2018
www.cpc.ncep.noaa.gov/data/indices/
NOAA's Earth System Research Laboratory
2018
www.esrl.noaa.gov/
NOAA's Science Data Integration Group Live Access Server
2018
ferret.pmel.noaa.gov/LAS/documentation/las-servers
Nonlinearity and Asymmetry of ENSO
Soon Il-An and Fei-Fei Jin - Journal of Climate - 2003
journals.ametsoc.org/doi/pdf/10.1175/1520-0442%282004%29017%3C2399%3ANAAOE%3E2.0.CO%3B2
Reassessing biases and other uncertainties in sea-surface temperature observations measured in situ since 1850, part I: measurement and sampling uncertainties
J. J. Kennedy, N. A. Rayner, and R. O. Smith et al - American Geophysical Union - 2011
www.metoffice.gov.uk/hadobs/hadsst3/part_1_figinline.pdf
Reassessing biases and other uncertainties in sea-surface temperature observations measured in situ since 1850, part 2: biases and homogenization
J. J. Kennedy, N. A. Rayner, and R. O. Smith et al - American Geophysical Union - 2011
www.metoffice.gov.uk/hadobs/hadsst3/part_2_figinline.pdf
Subsurface Nonlinear Dynamical Heating and ENSO asymmetry
Michuta Hayashi and Fei-Fei Jin - Geophysical Research Letters - 2017
agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017GL075771
Super El Nino
Li-Ciao Hong - Springer - 2016
https://books.google.com/books?hl=en&lr=&id=QJOVCwAAQBAJ&oi=fnd&pg=PR5&dq=super+el+nino&ots=dDOUCCDtlL&sig=d0-HIXFxUDunWm2bfYa8Prt33Mc
The Effect on the Intraseasonal Variance of Surface Temperatures in Winter
Catherine A. Smith and Prashant D. Sardeshmukh - International Journal of Climatology - 2000
rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/1097-0088%2820001115%2920%3A13%3C1543%3A%3AAID-JOC579%3E3.0.CO%3B2-A
The ERA-Interim reanalysis: configuration and performance of the data assimilation system
D. Dee, S. Uppala, and A. Simmons et al - Quarterly Journal Of the Royal Meteorological Society - 2011
rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/qj.828
The Met Office Hadley Centre sea ice and sea surface temperature data set, version 2: 1. Sea ice concentrations
Holly A. Titchner and Nick A. Rayner - Journal of Geophysical Research: Atmospheres - 2014
https://www.metoffice.gov.uk/hadobs/hadisst2/Titchner_and_Rayner2014.pdf
The NCEP Climate Forecast System Reanalysis
Suranjana Saha, Shrinivas Moorthi, and Hua-Lu Pan et al - BAMS - 2010
journals.ametsoc.org/doi/pdf/10.1175/2010BAMS3001.1
The Twentieth Century Reanalysis Project
G.P. Compo, J. S. Whitaker, and P. D. Sardeshmukh et al - Quarterly Journal of the Royal Meteorological Society - 2011
rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/qj.776
Alexey Kaplan, Mark Cane, and Yochanan Kushnir et al - Journal Of Geophysical Research: Oceans - 1998
agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/97JC01736
An Analysis Of the 1877–78 ENSO Episode and Comparison with 1982–83
George Kiladis and Henry Diaz - Monthly Weather Review - 1986
journals.ametsoc.org/doi/pdf/10.1175/1520-0493%281986%29114%3C1035%3AAAOTEE%3E2.0.CO%3B2
An ensemble data set of sea-surface temperature change from 1850: the Met Office Hadley Centre HADSST.4.0.0.0 data set
J.J. Kennedy et al - 2019
https://www.metoffice.gov.uk/hadobs/hadsst4/HadSST4_accepted.pdf
An Improved In Situ and Satellite SST Analysis For Climate
Richard Reynolds, Nick Rayner, Thomas Smith, Diane Stokes, and Wanqiu Wang - Journal Of Climate - 2002
ftp.emc.ncep.noaa.gov/cmb/sst/papers/oiv2pap/oiv2.pdf
Aqua: an Earth-observing Satellite Mission To Examine Water and Other Climate Variables
C.l. Parkinson - Ieee Transactions on Geoscience and Remote Sensing - 2003
ieeexplore.ieee.org/abstract/document/1196036/
A Real-time Global Sea Surface Temperature Analysis
Richard Reynolds - Journal Of Climate - 1988
journals.ametsoc.org/doi/pdf/10.1175/1520-0442%281988%29001%3C0075%3AARTGSS%3E2.0.CO%3B2
A Reanalysis Of the Extended Multivariate Enso Index (MEI.ext) and Comparison Of the 1877-78 and 2015-16 El Nino Events
Webb, Eric James - 2017
ams.confex.com/ams/97Annual/webprogram/Paper317006.html
Bivariate EnSo Timeseries or the "BEST" ENSO Index
Physical Sciences Division-ESRL Team - 2018
www.esrl.noaa.gov/psd/people/cathy.smith/best/
Centennial-scale Sea Surface Temperature Analysis and Its Uncertainty
Shoji Hirahara, Masayoshi Ishii, and Yoshikazu Fukuda - Journal Of Climate - 2014
journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-12-00837.1
CERA-20C: A Coupled Reanalysis Of the Twentieth Century
Patrick Laloyaux, Eric Boisseson, and Magdalena Balmaseda et al - Journal Of Advances in Modeling Earth Systems - 2018
agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2018MS001273
Cold and Warm Episodes by Season
NOAA's Climate Prediction Center - 2018
origin.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ONI_v5.php
Documentation Of a highly ENSO‐related sst region in the equatorial pacific: Research note
Anthony Bamston, Muthuvel Chelliah, and Stanley Goldenberg - Atmosphere-ocean - 1997
www.tandfonline.com/doi/pdf/10.1080/07055900.1997.9649597?needAccess=true
ECMWF Climate Reanalysis
Sarah Keeley - 2018
www.ecmwf.int/en/research/climate-reanalysis
El Niño and Climate Change
Kevin Trenberth and Timothy Hoar - Geophysical Research Letters - 1997
agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/97GL03092
El Nino and La Nina Years and Intensities
Jan Null - 2018
ggweather.com/enso/oni.htm
El Nino/Southern Oscillation behaviour since 1871 as diagnosed in an Extended Multivariate ENSO index (MEI.ext)
Klaus Wolter and Michael Timlin - International Journal Of Climatology - 2011
rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/joc.2336
Equatorial Pacific Sea Surface Temperatures
NOAA's National Centers for Environmental Information - 2018
www.ncdc.noaa.gov/teleconnections/enso/indicators/sst/
ERA-20C: An Atmospheric Reanalysis of the Twentieth Century
Paul Poli, Hans Hersbach, and Dick Dee et al- Journal Of Climate - 2016
journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-15-0556.1
ERA-20CM: a twentieth century atmospheric model ensemble
Hans Hersbach, Carole Peubey, and Adrian Simmons et al - Quarterly Journal Of the Royal Meteorological Society - 2015
rmets.onlinelibrary.wiley.com/doi/pdf/10.1002/qj.2528
Extended Multivariate ENSO Index (MEI.ext)
Klaus Wolter - NOAA's ESRL PSD - 2018
www.esrl.noaa.gov/psd/enso/mei.ext/
Extended Reconstructed Sea Surface Temperature, Version 4 (ERSSTv4). Part I: Upgrades and Intercomparisons
Boyin Huang, Viva Banzon, and Eric Freeman et al - Journal Of Climate - 2015
journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-14-00006.1
Extended Reconstructed Sea Surface Temperature, Version 4 (ERSSTv4): Part II: Parametric and Structural Uncertainty Estimations
Wei Liu, Boyin Huang, and Peter Thorne et al - Journal Of Climate - 2015
journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-14-00007.1
Extended Reconstructed Sea Surface Temperature, Version 5 (ERSSTv5): Upgrades, Validations, Intercomparisons
Boyin Huang, Peter Thorne, and Viva Banzon et al - Journal Of Climate - 2017
journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-16-0836.1
Further Exploring and Quantifying Uncertainties for Extended Reconstructed Sea Surface Temperature (ERSST) Version 4 (V4)
Boyin Huang, Peter Thorne, and Thomas Smith et al - Journal Of Climate - 2016
journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-15-0430.1
Global analyses of sea surface temperature, sea ice, and night marine air temperature since the late nineteenth century
N. Rayner, D. E. Parker, and E.B. Horton et al
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2002JD002670
Global Climate Observing System Working Group on Surface Pressure (WG-SP)
2018
www.esrl.noaa.gov/psd/gcos_wgsp/
ICOADS 3.0: a major update to the historical marine record
Eric Freeman, Scott Woodruff, and Steven Worley et al - International Journal Of Climatology - 2016
rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/joc.4775
Improved Analyses of Changes and Uncertainties in Sea Surface Temperature Measured In Situ since the Mid-Nineteenth Century: The HADSST2 Dataset
N. A. Rayner, P. Brohan, and D. E. Parker et al - Journal of Climate - 2005
hadobs.metoffice.com/hadsst2/rayner_etal_2005.pdf
Improved Global Sea Surface Temperature Analyses Using Optimum Interpolation
Richard Reynolds and Thomas Smith - Journal Of Climate - 1994
journals.ametsoc.org/doi/pdf/10.1175/1520-0442%281994%29007%3C0929%3AIGSSTA%3E2.0.CO%3B2
Improvements to NOAA's Historical Merged Land-Ocean Surface Temperature Analysis (1880-2006)
Thomas Smith, Richard Reynolds, Thomas Peterson, and Jay Lawrimore - Journal Of Climate - 2008
journals.ametsoc.org/doi/pdf/10.1175/2007JCLI2100.1
Notes and Correspondence: Interdecadal Changes of 30-Yr SST Normals during 1871-2000
Yan Xue, Thomas M. Smith, and Richard W. Reynolds - Journal of Climate - 2002
journals.ametsoc.org/doi/pdf/10.1175/1520-0442%282003%29016%3C1601%3AICOYSN%3E2.0.CO%3B2
International Research Institute for Climate and Society
2018
iri.columbia.edu/
Koninklijk Nederlands Meterologisch Instituut (KNMI) Climate Explorer
2018
climexp.knmi.nl/start.cgi?id=someone@somewhere
Measuring the Strength of ENSO events - how does 1997/98 rank?
Klaus Wolter and Michael S. Timlin - Royal Meteorological Society - 1998
www.esrl.noaa.gov/psd/enso/mei/WT2.pdf
Met Office Hadley Centre observations datasets
2018
www.metoffice.gov.uk/hadobs/
MERRA: NASA's Modern-era Retrospective Analysis for Research and Applications
Michele Rienecker, Max Suarez, and Ronald Gelaro et al - Journal Of Climate - 2011
journals.ametsoc.org/doi/pdf/10.1175/JCLI-D-11-00015.1
Monitoring ENSO in COADS with a Seasonally Adjusted Principal Component Index
Klaus Wolter and Michael S. Timlin - 17th Climate Diagnostics Workshop
www.esrl.noaa.gov/psd/enso/mei/WT1.pdf
Multidecade Global Flux Datasets from the Objectively Analyzed Air-sea Fluxes (OAFlux) Project: Latent and Sensible Heat Fluxes, Ocean Evaporation, and Related Surface Meteorological Variables
Lisan Yu, Xiangze Jin, and Robert A. Weller - Woods Hole Oceanographic Institute - 2008
oaflux.whoi.edu/pdfs/OAFlux_TechReport_3rd_release.pdf
Multivariate ENSO Index
Klaus Wolter - NOAA's ESRL PSD - 2018
www.esrl.noaa.gov/psd/enso/mei/
NASA Earth Observations
2018
neo.sci.gsfc.nasa.gov/view.php?datasetId=MYD28M
NCAR's Research Data Archive
2018
rda.ucar.edu/
NCEP-DOE AMIP-II Reanalysis (R-2)
Masao Kanamitsu, Wesley Ebisuzaki, and Jack Woollen et al - Bulletin Of the American Meteorological Society - 2002
journals.ametsoc.org/doi/pdf/10.1175/BAMS-83-11-1631
NOAA's Climate Prediction Center: Monthly Atmospheric & SST Indices
2018
www.cpc.ncep.noaa.gov/data/indices/
NOAA's Earth System Research Laboratory
2018
www.esrl.noaa.gov/
NOAA's Science Data Integration Group Live Access Server
2018
ferret.pmel.noaa.gov/LAS/documentation/las-servers
Nonlinearity and Asymmetry of ENSO
Soon Il-An and Fei-Fei Jin - Journal of Climate - 2003
journals.ametsoc.org/doi/pdf/10.1175/1520-0442%282004%29017%3C2399%3ANAAOE%3E2.0.CO%3B2
Reassessing biases and other uncertainties in sea-surface temperature observations measured in situ since 1850, part I: measurement and sampling uncertainties
J. J. Kennedy, N. A. Rayner, and R. O. Smith et al - American Geophysical Union - 2011
www.metoffice.gov.uk/hadobs/hadsst3/part_1_figinline.pdf
Reassessing biases and other uncertainties in sea-surface temperature observations measured in situ since 1850, part 2: biases and homogenization
J. J. Kennedy, N. A. Rayner, and R. O. Smith et al - American Geophysical Union - 2011
www.metoffice.gov.uk/hadobs/hadsst3/part_2_figinline.pdf
Subsurface Nonlinear Dynamical Heating and ENSO asymmetry
Michuta Hayashi and Fei-Fei Jin - Geophysical Research Letters - 2017
agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2017GL075771
Super El Nino
Li-Ciao Hong - Springer - 2016
https://books.google.com/books?hl=en&lr=&id=QJOVCwAAQBAJ&oi=fnd&pg=PR5&dq=super+el+nino&ots=dDOUCCDtlL&sig=d0-HIXFxUDunWm2bfYa8Prt33Mc
The Effect on the Intraseasonal Variance of Surface Temperatures in Winter
Catherine A. Smith and Prashant D. Sardeshmukh - International Journal of Climatology - 2000
rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/1097-0088%2820001115%2920%3A13%3C1543%3A%3AAID-JOC579%3E3.0.CO%3B2-A
The ERA-Interim reanalysis: configuration and performance of the data assimilation system
D. Dee, S. Uppala, and A. Simmons et al - Quarterly Journal Of the Royal Meteorological Society - 2011
rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/qj.828
The Met Office Hadley Centre sea ice and sea surface temperature data set, version 2: 1. Sea ice concentrations
Holly A. Titchner and Nick A. Rayner - Journal of Geophysical Research: Atmospheres - 2014
https://www.metoffice.gov.uk/hadobs/hadisst2/Titchner_and_Rayner2014.pdf
The NCEP Climate Forecast System Reanalysis
Suranjana Saha, Shrinivas Moorthi, and Hua-Lu Pan et al - BAMS - 2010
journals.ametsoc.org/doi/pdf/10.1175/2010BAMS3001.1
The Twentieth Century Reanalysis Project
G.P. Compo, J. S. Whitaker, and P. D. Sardeshmukh et al - Quarterly Journal of the Royal Meteorological Society - 2011
rmets.onlinelibrary.wiley.com/doi/epdf/10.1002/qj.776