MEI Index (last update: 5 June 2009)
Bimonthly MEI values (in 1/1000 of standard deviations), starting with Dec1949/Jan1950, thru last
month. More information on the MEI can be found on the MEI homepage.
Missing values are left blank. Note that values can still change with each monthly update, even
though such changes are typically smaller than +/-0.1. All values are normalized for each bimonthly
season so that the 44 values from 1950 to 1993 have an average of zero and a standard deviation of "1".
Responses to 'FAQ' can be found below this table:
YEAR DECJAN JANFEB FEBMAR MARAPR APRMAY MAYJUN JUNJUL JULAUG AUGSEP SEPOCT OCTNOV NOVDEC
1950 -1.043 -1.145 -1.278 -1.037 -1.42 -1.372 -1.312 -1.059 -.587 -.392 -1.145 -1.233
1951 -1.059 -1.213 -1.218 -.457 -.266 .389 .751 .873 .847 .745 .72 .47
1952 .413 .135 .094 .22 -.308 -.662 -.195 -.142 .379 .328 -.326 -.095
1953 .046 .388 .225 .68 .825 .238 .433 .255 .561 .102 .063 .31
1954 -.026 -.039 .125 -.599 -1.465 -1.547 -1.412 -1.431 -1.176 -1.357 -1.1 -1.114
1955 -.765 -.7 -1.2 -1.652 -1.651 -2.245 -1.884 -1.995 -1.779 -1.761 -1.853 -1.862
1956 -1.422 -1.286 -1.367 -1.185 -1.362 -1.505 -1.194 -1.115 -1.352 -1.468 -1.075 -1.026
1957 -.978 -.406 .13 .389 .882 .759 .959 1.109 1.168 1.098 1.122 1.189
1958 1.471 1.47 1.34 .925 .751 .882 .676 .378 .065 .094 .434 .704
1959 .537 .804 .487 .182 .027 -.009 -.21 .063 -.018 -.103 -.181 -.266
1960 -.301 -.259 -.076 -.019 -.34 -.261 -.316 -.252 -.515 -.388 -.337 -.433
1961 -.201 -.238 -.038 .043 -.291 -.129 -.251 -.323 -.345 -.568 -.393 -.647
1962 -1.086 -.994 -.755 -1.034 -.92 -.819 -.79 -.541 -.51 -.67 -.659 -.514
1963 -.74 -.853 -.677 -.763 -.431 -.074 .384 .658 .753 .878 .949 .717
1964 .858 .469 -.338 -.673 -1.27 -1.126 -1.378 -1.535 -1.293 -1.192 -1.251 -.925
1965 -.534 -.309 -.216 .119 .524 .942 1.435 1.516 1.449 1.234 1.377 1.266
1966 1.327 1.183 .674 .474 -.141 -.177 -.114 .165 -.111 -.045 .026 -.163
1967 -.462 -.921 -1.071 -1.03 -.408 -.313 -.621 -.494 -.697 -.712 -.42 -.388
1968 -.637 -.758 -.624 -.968 -1.066 -.757 -.493 -.142 .204 .442 .589 .365
1969 .676 .834 .397 .584 .71 .799 .434 .271 .211 .499 .664 .364
1970 .355 .384 .181 -.077 -.153 -.679 -1.097 -1.011 -1.236 -1.098 -1.084 -1.229
1971 -1.193 -1.497 -1.793 -1.851 -1.452 -1.467 -1.237 -1.266 -1.473 -1.442 -1.384 -1.034
1972 -.562 -.373 -.212 -.125 .538 1.129 1.816 1.766 1.539 1.615 1.708 1.76
1973 1.771 1.513 .827 .495 -.124 -.767 -1.073 -1.358 -1.707 -1.675 -1.48 -1.835
1974 -1.913 -1.792 -1.706 -1.582 -1.007 -.653 -.801 -.694 -.611 -1.008 -1.225 -.893
1975 -.51 -.579 -.904 -.98 -.881 -1.183 -1.504 -1.691 -1.821 -1.938 -1.758 -1.784
1976 -1.613 -1.384 -1.266 -1.195 -.505 .276 .615 .712 1.027 .914 .42 .541
1977 .499 .285 .147 .56 .371 .488 .847 .688 .78 .998 1.004 .895
1978 .778 .898 .974 .18 -.352 -.532 -.377 -.203 -.354 .007 .24 .406
1979 .606 .373 .009 .308 .426 .47 .374 .629 .792 .692 .751 1.035
1980 .655 .567 .699 .891 .912 .882 .788 .365 .259 .196 .241 .104
1981 -.294 -.205 .417 .635 .072 -.027 -.038 -.137 .135 .118 -.012 -.154
1982 -.294 -.175 .084 -.056 .455 .994 1.605 1.77 1.797 2.031 2.459 2.447
1983 2.726 2.962 3.109 2.994 2.555 2.23 1.768 1.198 .49 .041 -.148 -.189
1984 -.355 -.529 .17 .387 .106 -.137 -.199 -.242 -.103 .023 -.306 -.583
1985 -.563 -.6 -.732 -.477 -.738 -.137 -.196 -.426 -.563 -.136 -.046 -.28
1986 -.308 -.204 .066 -.107 .328 .312 .392 .732 1.105 1.02 .858 1.191
1987 1.249 1.174 1.714 1.878 2.128 1.925 1.833 2.008 1.885 1.641 1.224 1.271
1988 1.119 .671 .458 .288 .088 -.653 -1.196 -1.326 -1.553 -1.372 -1.492 -1.348
1989 -1.123 -1.266 -1.024 -.75 -.497 -.316 -.479 -.553 -.27 -.343 -.07 .156
1990 .229 .529 .852 .411 .572 .436 .097 .109 .424 .309 .369 .344
1991 .311 .296 .375 .35 .686 1.04 1.018 1.035 .722 1.005 1.173 1.256
1992 1.714 1.849 1.986 2.246 2.109 1.799 1.017 .588 .482 .6 .525 .621
1993 .64 .941 .956 1.38 1.983 1.558 1.123 1.049 1.002 1.041 .828 .582
1994 .384 .191 .126 .449 .618 .622 .827 .616 .638 1.345 1.238 1.188
1995 1.174 .883 .805 .342 .456 .477 .283 .045 -.359 -.439 -.488 -.503
1996 -.605 -.62 -.263 -.524 -.234 -.013 -.176 -.265 -.335 -.388 -.11 -.351
1997 -.424 -.488 -.195 .479 1.107 2.317 2.646 2.872 2.83 2.192 2.308 2.203
1998 2.4 2.663 2.635 2.553 1.964 1.144 .342 -.212 -.598 -.822 -1.11 -.965
1999 -1.042 -1.11 -.997 -.978 -.67 -.386 -.527 -.737 -.884 -.943 -1.054 -1.212
2000 -1.127 -1.186 -1.04 -.435 .016 -.26 -.219 -.168 -.248 -.335 -.744 -.634
2001 -.53 -.682 -.61 -.154 .151 -.001 .146 .287 -.237 -.335 -.252 -.044
2002 -.012 -.175 -.135 .378 .885 .842 .556 .856 .768 .895 .972 1.142
2003 1.23 .909 .794 .356 .037 -.004 .037 .259 .451 .552 .535 .34
2004 .313 .361 -.131 .243 .44 .268 .455 .612 .56 .516 .808 .675
2005 .302 .742 .924 .538 .708 .463 .422 .42 .192 -.263 -.399 -.532
2006 -.387 -.464 -.611 -.646 -.02 .469 .638 .736 .844 .989 1.265 .953
2007 .996 .491 .097 .041 .165 -.308 -.293 -.442 -1.127 -1.129 -1.133 -1.131
2008 -.958 -1.359 -1.566 -.903 -.389 .05 .028 -.206 -.569 -.739 -.563 -.633
2009 -.695 -.725 -.737 -.191 .344
(1) If you are trying to relate the MEI to monthly values of, say, precipitation, it may be
expedient to use the MEI value of month(i-1) and month(i) as if it were the value for
month(i) only. Since it takes a week or so for the global atmosphere to respond to tropical
SST anomalies, the resulting lag is thus built into the analysis (I have verified this for
southwest U.S. precipitation).
(2) Next update: 7 July 2009
(3) Are there MEI values available prior to 1950? YES (I have some), and NO (I do not deem them
fit for distribution yet). Since I am currently working on other projects, I cannot foresee
when I will get to finalizing such historic MEI analyses. Based on preliminary data quality
analyses, such values would be most reliable around 1900. Aside from the World Wars, the
biggest problem is the decreased importance of ENSO during the 1920-50 period, as well as
big changes in observing techniques around 1941 in particular. Let me know if you are
interested in such historical MEI values, and I will keep you in mind for future updates on this.
(4) Why do I believe that the MEI is better for monitoring ENSO than the SOI or various SST
indices? In brief, the MEI integrates more information than other indices, it reflects
the nature of the coupled ocean-atmosphere system better than either component, and it is
less vulnerable to occasional data glitches in the monthly update cycles. Now, if you are
interested in ENSO impacts in a very specific part of the world, I would suggest that you
obtain other ENSO indices as well and establish which one best fits your needs.
For instance, in Australia, Darwin sea level pressure and/or the SOI may be more appropriate
than the MEI. My claim here is that the MEI does a better job than other indices for the
overall monitoring of the ENSO phenomenon, including, for instance, world-wide correlations
with surface temperatures and rainfall.
(5) I have been asked about MEI-like indices for the Indian Ocean, and at present I have no such
project under way, nor do I know of any such data.
(6) Given the integrative approach of the MEI, I am very hesitant to give out subsets of the data
that make up the MEI (for instance, its SST or SLP components alone). Therefore, I will not
honor requests of that nature.
(7) If you are interested in MEI predictions, please contact me directly under my e-mail address:
Klaus Wolter (klaus.wolter@noaa.gov).
Link to ranked MEI values is here.
Go back to MEI homepage.