Monthly Multivariate ENSO Index (MEI)
Entry ID: NOAA_NWS_CPC_MEI

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Summary
Abstract: [Text Source: Klaus Wolter, http://www.esrl.noaa.gov/psd//people/klaus.wolter/MEI/
Refer to: Wolter and Timlin, 1993, 1998, http://www.esrl.noaa.gov/psd//people/klaus.wolter/MEI/#ref_wt1 ]

El Niño/Southern Oscillation (ENSO) is the most important coupled ocean-atmosphere phenomenon to cause global climate variability on interannual time scales. Here we attempt to monitor ENSO by basing the Multivariate ENSO Index (MEI) on the six main observed variables over the tropical Pacific. These six variables are: sea-level pressure (P), zonal (U) and meridional (V) components of the surface wind, sea surface temperature (S), surface air temperature (A), and total cloudiness fraction of the sky (C). These observations have been collected and published in COADS for many years. The MEI is computed separately for each of twelve sliding bi-monthly seasons (Dec/Jan, Jan/Feb,..., Nov/Dec). After spatially filtering the individual fields into clusters (Wolter, 1987), the MEI is calculated as the first unrotated Principal Component (PC) of all six observed fields combined. This is accomplished by normalizing the total variance of each field first, and then performing the extraction of the first PC on the co-variance matrix of the combined fields (Wolter and Timlin, 1993). In order to keep the MEI comparable, all seasonal values are standardized with respect to each season and to the 1950-93 reference period. The MEI is extended during the first week of the following month based on near-real time marine ship and buoy observations (courtesy of Diane Stokes at NCEP) summarized into COADS-compatible 2-degree monthly statistics at NOAA-ESRL PSD. Caution should be exercised when interpreting the MEI on a month-to-month basis, since the input data for updates are not as reliable as COADS, and the MEI has been developed mainly for research purposes. Negative values of the MEI represent the cold ENSO phase, a.k.a.La Niña, while positive MEI values represent the warm ENSO phase (El Niño).

See: http://www.esrl.noaa.gov/psd//people/klaus.wolter/MEI/

Related URL
Link: GET DATA
Description: Access to monthly MEI index data since 1950


Link: GET DATA
Description: Current MEI time series


Link: VIEW RELATED INFORMATION
Description: Access to additional MEI data, plots and documentation.


Geographic Coverage
 N: 5.0 S: -5.0  E: -120.0  W: -170.0

Data Set Citation
Dataset Originator/Creator: NOAA/OAR/ESRL/PSD
Dataset Title: Multivariate ENSO Index (MEI)
Dataset Series Name: NOAA Indices and Forecasts
Dataset Release Date: ongoing
Dataset Release Place: Boulder, CO, USA
Dataset Publisher: NOAA/OAR/ESRL/PSD
Online Resource: http://www.esrl.noaa.gov/psd//people/klaus.wolter/MEI/


Temporal Coverage
Start Date: 1950-01-01


Location Keywords
OCEAN > PACIFIC OCEAN


Data Resolution
Temporal Resolution: monthly


Science Keywords
OCEANS >OCEAN TEMPERATURE >SEA SURFACE TEMPERATURE >SST    [Definition]
CLIMATE INDICATORS >ATMOSPHERIC/OCEAN INDICATORS >TELECONNECTIONS >EL NINO SOUTHERN OSCILLATION (ENSO) >MULTIVARIATE ENSO INDEX    [Definition]


ISO Topic Category
CLIMATOLOGY/METEOROLOGY/ATMOSPHERE


Keywords
MEI
Multivariate ENSO Index
climate index
climate indices
SST
ENSO
climate change


Data Set Progress
IN WORK


Originating Center
NOAA/NWS/CPC


Data Center
Physical Sciences Division, Earth System Research Laboratory, OAR, NOAA, U.S. Department of Commerce    [Information]
Data Center URL: http://www.esrl.noaa.gov/psd/
Dataset ID: MEI Index

Data Center Personnel
Name: ESRL/PSD DATA INQUIRIES
Email: esrl.psd.data at noaa.gov



Distribution
Distribution_Media: online www
Distribution_Format: ascii
Fees: none


Personnel
KLAUS WOLTER
Role: TECHNICAL CONTACT
Email: Klaus.Wolter at noaa.gov


SCOTT A. RITZ
Role: DIF AUTHOR
Phone: 301-614-5126
Fax: 301-614-5268
Email: Scott.A.Ritz at nasa.gov
Contact Address:
NASA Goddard Space Flight Center
Global Change Master Directory
City: Greenbelt
Province or State: Maryland
Postal Code: 20771
Country: USA


Publications/References
Wolter, K., and M.S. Timlin, 1998: Measuring the strength of ENSO -
how does 1997/98 rank? Weather, 53, 315-324

Rasmusson, E.G., and T.H. Carpenter, 1982: Variations in tropical sea
surface temperature and surface wind fields associated with the
Southern Oscillation/El NiC1o. Mon. Wea. Rev., 110, 354-384.

Wolter, K., 1987: The Southern Oscillation in surface circulation and
climate over the tropical Atlantic, Eastern Pacific, and Indian Oceans
as captured by cluster analysis. J. Climate Appl. Meteor., 26,
540-558.

Wolter, K., and M.S. Timlin, 1993: Monitoring ENSO in COADS with a
seasonally adjusted principal component index. Proc. of the 17th
Climate Diagnostics Workshop, Norman, OK, NOAA/N MC/CAC, NSSL,
Oklahoma Clim. Survey, CIMMS and the School of Meteor., Univ. of
Oklahoma, 52-57.

Creation and Review Dates
DIF Creation Date: 2005-12-13
Last DIF Revision Date: 2009-11-02

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