MEI Index (last update: 3 May 2008)
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 -1.05 -1.146 -1.275 -1.037 -1.411 -1.372 -1.311 -1.06 -.6 -.408 -1.149 -1.24
1951 -1.065 -1.209 -1.219 -.464 -.26 .389 .75 .871 .839 .743 .722 .473
1952 .419 .147 .105 .222 -.303 -.663 -.196 -.148 .371 .32 -.331 -.096
1953 .047 .392 .239 .683 .826 .239 .433 .257 .556 .11 .075 .315
1954 -.024 -.041 .118 -.606 -1.489 -1.547 -1.412 -1.436 -1.189 -1.366 -1.099 -1.116
1955 -.764 -.69 -1.188 -1.654 -1.647 -2.245 -1.885 -1.995 -1.777 -1.766 -1.858 -1.862
1956 -1.425 -1.295 -1.368 -1.183 -1.356 -1.505 -1.195 -1.117 -1.352 -1.471 -1.078 -1.03
1957 -.973 -.409 .111 .389 .884 .76 .959 1.11 1.163 1.096 1.116 1.19
1958 1.467 1.461 1.326 .92 .743 .881 .674 .378 .068 .083 .422 .692
1959 .526 .798 .495 .176 .015 -.01 -.21 .061 -.027 -.108 -.181 -.264
1960 -.298 -.251 -.08 -.02 -.345 -.261 -.316 -.253 -.512 -.386 -.338 -.436
1961 -.207 -.238 -.035 .043 -.287 -.129 -.252 -.328 -.351 -.578 -.397 -.644
1962 -1.086 -.999 -.768 -1.036 -.914 -.819 -.789 -.54 -.508 -.674 -.665 -.52
1963 -.748 -.873 -.7 -.769 -.437 -.074 .382 .655 .752 .868 .944 .713
1964 .856 .477 -.336 -.675 -1.277 -1.127 -1.379 -1.536 -1.295 -1.194 -1.26 -.935
1965 -.54 -.318 -.227 .115 .524 .942 1.436 1.516 1.452 1.231 1.375 1.265
1966 1.325 1.185 .679 .471 -.154 -.177 -.115 .164 -.121 -.058 .019 -.171
1967 -.465 -.912 -1.068 -1.032 -.413 -.313 -.62 -.5 -.705 -.728 -.426 -.396
1968 -.649 -.785 -.659 -.973 -1.085 -.758 -.494 -.145 .192 .432 .585 .364
1969 .672 .831 .409 .585 .719 .799 .434 .277 .213 .501 .671 .369
1970 .357 .38 .177 -.074 -.154 -.679 -1.096 -1.009 -1.241 -1.094 -1.079 -1.221
1971 -1.192 -1.501 -1.794 -1.848 -1.444 -1.466 -1.236 -1.265 -1.467 -1.439 -1.384 -1.028
1972 -.555 -.37 -.224 -.127 .534 1.13 1.815 1.763 1.555 1.627 1.722 1.771
1973 1.775 1.528 .852 .498 -.125 -.767 -1.072 -1.354 -1.697 -1.66 -1.471 -1.828
1974 -1.913 -1.795 -1.711 -1.582 -.999 -.652 -.801 -.698 -.615 -1.007 -1.223 -.893
1975 -.508 -.571 -.898 -.978 -.863 -1.181 -1.503 -1.687 -1.812 -1.927 -1.75 -1.781
1976 -1.611 -1.376 -1.254 -1.191 -.48 .277 .617 .715 1.028 .911 .429 .545
1977 .502 .287 .159 .563 .369 .488 .847 .69 .774 .992 1.001 .89
1978 .77 .892 .958 .18 -.358 -.533 -.379 -.207 -.357 .002 .231 .406
1979 .611 .383 .022 .31 .423 .47 .376 .628 .797 .702 .752 1.032
1980 .651 .552 .693 .892 .907 .882 .788 .368 .268 .201 .247 .099
1981 -.299 -.215 .418 .636 .078 -.027 -.037 -.14 .129 .125 -.007 -.151
1982 -.288 -.179 .083 -.057 .443 .994 1.604 1.764 1.799 2.031 2.456 2.448
1983 2.725 2.958 3.104 2.992 2.567 2.231 1.77 1.211 .515 .063 -.139 -.187
1984 -.347 -.52 .167 .392 .12 -.136 -.198 -.241 -.101 .026 -.305 -.58
1985 -.559 -.596 -.706 -.471 -.741 -.138 -.197 -.426 -.559 -.134 -.052 -.28
1986 -.307 -.217 .042 -.107 .319 .311 .39 .722 1.092 1.02 .859 1.188
1987 1.253 1.179 1.703 1.877 2.128 1.924 1.833 2.011 1.897 1.654 1.233 1.28
1988 1.129 .682 .477 .295 .091 -.653 -1.195 -1.315 -1.534 -1.359 -1.484 -1.338
1989 -1.109 -1.245 -1.02 -.743 -.491 -.315 -.479 -.55 -.269 -.336 -.069 .152
1990 .231 .544 .87 .412 .566 .436 .098 .107 .42 .316 .373 .343
1991 .312 .292 .372 .35 .689 1.041 1.019 1.039 .726 1.006 1.172 1.254
1992 1.712 1.845 1.992 2.246 2.106 1.798 1.018 .591 .472 .586 .513 .619
1993 .642 .936 .956 1.38 1.982 1.558 1.125 1.052 1.009 1.046 .83 .592
1994 .392 .197 .133 .451 .62 .622 .828 .615 .636 1.331 1.241 1.195
1995 1.174 .874 .784 .339 .447 .478 .283 .051 -.346 -.427 -.48 -.499
1996 -.601 -.619 -.266 -.519 -.232 -.012 -.175 -.261 -.328 -.374 -.103 -.35
1997 -.424 -.489 -.188 .48 1.1 2.316 2.648 2.876 2.847 2.217 2.33 2.217
1998 2.404 2.67 2.652 2.557 1.987 1.144 .345 -.194 -.567 -.79 -1.085 -.945
1999 -1.024 -1.081 -.957 -.962 -.644 -.384 -.526 -.729 -.873 -.924 -1.043 -1.208
2000 -1.113 -1.168 -1.017 -.422 .034 -.258 -.218 -.168 -.238 -.326 -.733 -.624
2001 -.516 -.661 -.587 -.142 .164 0 .147 .288 -.229 -.328 -.248 -.043
2002 -.008 -.162 -.111 .384 .883 .843 .557 .856 .776 .905 .982 1.148
2003 1.23 .907 .795 .359 .039 -.004 .039 .263 .452 .557 .54 .349
2004 .316 .364 -.114 .251 .442 .268 .457 .61 .561 .53 .816 .682
2005 .305 .742 .928 .54 .712 .464 .423 .426 .201 -.251 -.387 -.525
2006 -.377 -.44 -.585 -.637 -.011 .47 .639 .741 .859 1.012 1.277 .966
2007 1.011 .507 .104 .048 .179 -.307 -.291 -.434 -1.109 -1.117 -1.121 -1.121
2008 -.948 -1.34 -1.546 -.89
(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 June 2008
(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.