Learning about ENSO

Thought its about time l collected a few references for this important climate phenomena
I will add to the reference list by adding links to research and information as time goes by

CLICK on the HEADING of this post to load all further information and posts at the base of this page


n. “El Niño/Southern Oscillation; an occasional shift in winds and ocean currents, centered in the South Pacific region, with worldwide consequences for climate and biological systems.” (Source: Ricklefs)

trade wind relaxing by Bob tisdale
picture from Bob Tisdale from the link to his paper below

The first post is from an expert who pretty much studies ENSO full time from his blog

He has titled this post
ENSO Basics: Westerly Wind Bursts Initiate an El Niño

Posted on October 22, 2013

By weathercycles Posted in ENSO

39 comments on “Learning about ENSO

  1. This looks good. Posted by Mike Hauber a contributor on weather zone forum ENSO thread here

    Recent intensification of wind-driven circulation in the Pacific and the ongoing warming hiatus


    Despite ongoing increases in atmospheric greenhouse gases, the Earth’s global average surface air temperature has remained more or less steady since 2001. A variety of mechanisms have been proposed to account for this slowdown in surface warming. A key component of the global hiatus that has been identified is cool eastern Pacific sea surface temperature, but it is unclear how the ocean has remained relatively cool there in spite of ongoing increases in radiative forcing. Here we show that a pronounced strengthening in Pacific trade winds over the past two decades—unprecedented in observations/reanalysis data and not captured by climate models—is sufficient to account for the cooling of the tropical Pacific and a substantial slowdown in surface warming through increased subsurface ocean heat uptake. The extra uptake has come about through increased subduction in the Pacific shallow overturning cells, enhancing heat convergence in the equatorial thermocline. At the same time, the accelerated trade winds have increased equatorial upwelling in the central and eastern Pacific, lowering sea surface temperature there, which drives further cooling in other regions. The net effect of these anomalous winds is a cooling in the 2012 global average surface air temperature of 0.1–0.2 °C, which can account for much of the hiatus in surface warming observed since 2001. This hiatus could persist for much of the present decade if the trade wind trends continue, however rapid warming is expected to resume once the anomalous wind trends abate

    Matthew H. England,
    Shayne McGregor,
    Paul Spence,
    Gerald A. Meehl,
    Axel Timmermann,
    Wenju Cai,
    Alex Sen Gupta,
    Michael J. McPhaden,
    Ariaan Purich
    & Agus Santoso


  2. Viewing the strength of the westerly wind burst

    Thanks to ‘coastal storm ‘ from WZ forum for the link

    Here a wind anomaly map showing the wind anomalies across the global equator
    5 deg either side of the equator

    This map is hot linked and will update so you can see the current state of play

    850 hpa wind anomaly equatorial

    To see exactly where on the globe this anomaly is measured. I have marked on a map of the globe the forecast westerly wind anomaly along the equator this week 23rd-29th feb 2014

    I have linked the wind anomaly map with the equator longitudes

    The westerly wind burst is the red anomaly. Also marked on the globe as a red square

    westerly wind burst marked on global equator feb 23rd 2014

  3. Research article by Dr Peter Baines from CSIRO Atmospheric Research
    .El Nino Link To Southern Ocean Currents

    antartic circumpola rcurrent
    The Antarctic Circumpolar Wave occurs in the Circumpolar Current around Antarctica. The Current takes eight years to complete a full rotation of the earth, and influences Australia’s weather
    The Wave alternates large regions of slightly warmer and cooler water.
    Read on

  4. Thanks to Paul Vaughan for the link


    South Pacific convergence zone (SPCZ) . Its position in the Pacific ocean and links to ENSO phase

    A new index for variations in the position of the South Pacific convergence zone 1910/11-2011/2012
    Salinger, M. J.; McGree, Simon; Beucher, Florent; Power, Scott B.; Delage, François
    Extract from Abstract

    During El Niño episodes the SPCZ is displaced by about 1°-3° east, and La Niña events 1°-3° west of the mean position on average. The index indicates a striking movement eastward for the period 1977/78-1998/99, compared with 1944/45-1976/77 in association with the Interdecadal Pacific oscillation (IPO). The eastward movement of the SPCZ in the late twentieth century is related to significant precipitation trends in the South Pacific region. Since 1998/99 the SPCZ has regressed westward with the negative phase change of the IPO. The long-term trend in the SPCZI is very small relative to the interannual to decadal variability and is not statistically significant, suggesting that there has been little overall change in the mean position of the SPCZ over the past century.

  5. Trenberth et al 2014 have published a nice time series graph of ENSO. I like the ribbon color coding they have used here .
    Notice the change in frequency since 2005. The swings fro La Nina have been shorter. ( higher frequency)

    ENSO time series vs global temp anomlay by trenberth 2014

    ** Please note that the top graph uses the base period 1901-2000 and is the global mean surface temperature whereas
    the lower graph uses the base period 1950-1979 and is the SST anomaly for Niño 3.4

  6. Looking at Trenberths graphs above. Thought l would observe any lag between SST in Nino 3.4 and mean Global surface temperature
    The results show that the lag is very small (a small number of months)
    The SST Nino 3.4 change first and then the global temp a few months after.

    Nino 3.4  vsglobal mean temp time series. Calculating lag
    source of graph from Trenberth posted on..

    Thought l would use a ruler to measure how much warm anomaly and how much cool anomaly between 1968 – 2012 = 44 yrs ( the length Trenberth used to analyse here)

    At a very rough estimate . 55 5 % El Nino and 45 % La Nina
    Only a 10 % difference in length of time ( 44 yrs)
    Confirming proportionately more time in a warm anomaly phase leads to escalating global temps’

    I have not measured the amplitude which would improve the story

    The 10 % more time in a Nino 3.4 warm anomaly yielded a mean global temp’ increase of 0.7 deg c since 1970 ( 1968-2012)

    In 1983, the Nino 3.4 anomaly was 2.5 deg c and dropped down to minus 1.2 in 1985

    In 2 years the anomaly swung downward /changed by 3.7 deg c

    The global surface mean temp’ responded a few months after the Nino 3.4 drop and plunged ‘in sympathy’ from 0.3 deg c to 0.09 deg c. A drop of 0.21 deg c in 2 yrs

    So a change/drop in Nino 3.4 SST anomaly of 3.7 deg c , yielded a change in global mean temperature of 0.21 deg

    Ratio 3.7 : 0.21 = 17.61

    0.21 / 3.7 =

    ~0.1 deg c mean global temp change = 1.85 deg change in Nino 3.4 for the period 1983-85 anyway

    Please note these are ROUGH calculations .
    and this time period 1975-2005 is a warm phase of the PDO and AMO. check that

  7. I have never plotted correlation of major enso events and solar cycle

    a few of the larger events
    1918 la nina …was in solar cycle 15 ( 5yrs into cycle 15 ) approaching solar max
    1942 el nino ( 9 yrs into cycle 17) approaching solar minimum
    1975 la Nina ( 11yrs into the cycle 20 ) on solar minimum
    1982 El Nino ( 6 yrs into cycle 21) approaching or at solar max
    1997 El Nino ( 1 yr into solar cycle 23 ) close or on solar minimum
    2010 La Nina ( 3 yr in to SC 24 ) close to a minimum
    ( used list of solar cycles wikopedia)

    just grabbed these dates from ‘surly bonds’ accumulative SOI time series


    and hopefully the info above on placing these years on the SC is correct?

    4 major events were close or on solar minimum ( 1942, 1975, 1997, 2010)
    and 2 events were on or close to solar max( 1918, 1982)

  8. ROGER ANDREWS : some insight

    A few comments on your lead-off comments on El Niños, La Niñas and the solar cycle:

    The first graph on the attached plot shows 11 El Niños (Niño3.4 Index greater than 0.5) since 1966. They’re spaced between 3 and 7 years apart, have an average period of 4.4 years and show no obvious correlation with solar cycles, or at least none that I can see.

    The second graph shows eight La Niñas (Niño3.4 Index less than -0.5) since 1966, one of them double-pronged. They occur in four groups of two, with the two Niñas that make up the group spaced 3-4 years apart and the groups spaced 11 to 14 years apart. The three groups since 1982 show a consistent match with the sunspot cycle, with the first Niña peaking shortly before solar minimum and the second shortly before solar maximum. The 1969-73 group marches to the beat of a different drummer, but I suspect the 1976 PDO phase change may have something to do with that.

    enso vs solar cycle

    Temperature differential of the Pacific ocean (time series)
    “The commonly-used Niño indices give the impression that the central Pacific sloshes back and forth between warm and cold states. This is incorrect. Temperatures in the central Pacific “cold tongue” are almost always lower than temperatures in the “warm tongues” to the north and south, meaning that what we think of as the El Niño zone is in a near-permanent La Niña condition. What we call an El Niño is actually just a weaker-than-average La Niña and what we call a La Niña is actually just a stronger-than-average La Niña.

    The graph below plots what I call the Pacific Cold Tongue (PACT) Index, which I constructed some time ago and which I think is more definitive than the conventional ENSO indices. It’s calculated as the difference between mean SST in the “El Niño” zone (170W to 110W, 3N to 3S) and mean SST in the adjacent warm tongue zones to the north and south (170W to 110W, 3N to 10N and 3S to 10S). It turns briefly positive only twice – in 1982/83 and 1997/98. Otherwise the only significant change it shows is an abrupt decrease of about 0.3C in the average temperature difference and an accompanying increase in the amplitude of the fluctuations after 1982/83.


    My comment
    (Indicates the ENSO climate regime shift ~ 1975)

    PACT time series
    a copy at my photos here

  10. THE ONI


    Nice summary here with enso events weak, moderate and strong tabled

    The Oceanic Niño Index (ONI) has become the de-facto standard that NOAA uses for identifying El Niño (warm) and La Niña (cool) events in the tropical Pacific. It is the running 3-month mean SST anomaly for the Niño 3.4 region (i.e., 5oN-5oS, 120o-170oW). Events are defined as 5 consecutive overlapping 3-month periods at or above the +0.5o anomaly for warm (El Niño) events and at or below the -0.5 anomaly for cold (La Niña) events. The threshold is further broken down into Weak (with a 0.5 to 0.9 SST anomaly), Moderate (1.0 to 1.4) and Strong (≥ 1.5) events. For the purpose of this report for an event to be categorized as weak, moderate or strong it must have equaled or exceeded the threshold for at least 3 consecutive overlapping 3-month periods

    ENSO time series

  11. Range in AMPLITUDE of PACIFIC SST’s
    ” One can see that ENSO had more variance during 1880-1920 and also since 1950, with a relatively quiet period during 1920-1950. ”

    Pacific amplitude range ENSO time series

    Fig. 1. Sea surface temperatures averaged over the NINO3 region in the eastern Pacific (5°S-5°N, 90°W-150°W). Blue curve is low-pass filtered (>12 months) SST. Yellow background curve is running 15-year variance, plotted at mid-point of 15-year period. Curve has been reproduced upside-down to show “envelope” of variance.

    extracted from

  12. This a classic find by ROGER ANDREWS who posted this and was discussed on Tallbloke JUNE 2014

    Neutral events dominate during the upward phase of the schwabe cycle. This infers that the ocean and atmosphere do not couple to reinforce an ENSO event
    The ENSO events are on the downward slope of the schwabe. and thereabouts
    Interesting that no ENSO events around the 70-110 deg upward phase of the schwabe cycle
    the peak time for ENSO events is from schwabe max peak all the way down the declining sunspot phase of the schwabe cycle

    ENSO histogram vs solar cycle by Roger Andrews

  13. Multivariate ENSO index

    quote from BOB
    “There’s something else to consider about the MEI. El Niño and La Niña rankings according to the MEI aren’t based on fixed threshold values such as +0.5 for El Niño and -0.5 for La Niña. The MEI El Niño and La Niña rankings are based on percentiles, top 30% for the weak to strong El Niños and the bottom 30% for the weak to strong La Niñas. ”

    Comparing El Nino events using the MEI

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