CONCENTRATING THE EL NINO HEAT STREAM
This post is a continuation of one started a couple of days ago on the Weather 2016 thread, page 16.
Douglavers's post on March 5 got me digging into Argo in an attempt to visualize some of the mechanics
within the Pacific Ocean that are associated with the periodic warmings and coolings of the central and
eastern equatorial Pacific that we refer to as ENSO.
Doug's very astute comments.I suspect that most people do not know that El Ninos are actually planetary COOLING events.
If you want to get a system to lose heat you extract heat from all around that system and concentrate it in a few spots.
Stefan's Law then applies - net radiation from the system increases markedly. The system net cools.
This will be demonstrated when La Nina arrives.
This is probably one of the giant thermostatic systems of our planet.
I had become used to most descriptions of ENSO as being a largely west-to-east-and-back-again event. It would
appear that it is very much more than that. Part of this may be what Astromet was alluding to in his references to
northern and southern hemisphere annular modes (NAM, SAM). I don't pretend to understand these at this point, but it
appears perhaps that they may be linked to rearrangements in current patterns in the Pacific that helps concentrate
warmer water from the north and south central Pacific into the central and eastern equatorial Pacific during the warm
phase of ENSO. Thus ENSO has a north-south component as well as a west-east one. In this and the next three posts I will
present some of the data and visuals from Argo that seem to support this assessment. This may be found in the literature
somewhere, but, so far, I haven't found it ... maybe I just haven't dug deeply enough.
First, we know that the Southern Oscillation Index is directly related to ENSO, at least according to the literature. Negative
SOI values, which coincide with warm water movements eastward from the west Pacific warm pool, are associated with
higher than normal pressure over Darwin, Australia and lower than normal pressure over Tahiti. In chart number one below,
SOI values are shown to be directly associated with ENSO Index values since 1950. Low SOI values are directly correlated
with high sea surface temperature values in the Nino 3.4 area (5N-5S, 120-170W). This inverse relationship is shown in
chart number 2. Here, I have used Argo surface temperatures. This graph also shows that Argo surface temperatures in
the western equatorial Pacific decline as the Nino 3.4 region increases.
Chart 3 shows that there is also a direct relationship between sea surface temperatures (0-300 m) in areas between 20-35
Latitude and 140-180 West Longitude in both the northern and southern Pacific. As temperatures in the Nino 3.4 region
increase (associated with negative SOI values), water temperatures in these two areas decrease. You can see these
temperatures declining into the El Nino year of 2009-10 and the NOAA-designated El Nino years of 2014-2016. I include
2014 here because, as you will see in later graphs/maps, this large, east-Pacific warm-water event occurred over a period
of two years, unlike the 2009-10 event that occurred over one year. As I will show in cross-section slices, cold-water
currents in the north and south Pacific shift in these years from locations in the extreme east and west of the basins, which
are associated with the normal north and south Pacific gyres, to locations in the center of the basins between approximately
140-180 West ... and it is these surface currents that push warm water that has accumulated in the southern mid-latitude
areas into the eastward-moving stream of warm water along the equator. This process reverses in the post-Nino years
and these mid-latitude areas warm up again. Note that Chart 3 includes both monthly and 13-month temperature values.