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Questions and Responses
Posted February 15, 1998 |
previous set
Question:
I'm interested in information on El Niño in the South
Pacific, and how long it will last. We're planning a trip
there (Cook Islands) next September, and are wondering if
the weather will still be impacted by El Niño.
(name witheld by request)
Response:
The Cook islands are between New Zealand and Samoa, in the
southwest Pacific. By September, El Niño will have
faded away, but its alter ego La Niña may be active,
possibly influencing weather there. Let me explain a little.
El Niño's fancy scientific name is ENSO, and that
stands for El Niño-Southern Oscillation. The "Southern"
refers to the south Pacific, and some part of the mysterious
cyclic coming and going of El Niño is intimately tied
to the south Pacific and the atmosphere above it. Weather
records show that throughout the ENSO cycle of several
years, conditions on one side of the Pacific tend to be the
mirror opposite from the other side; this past year, for
example, we saw drought in the west and excessive rains in
the east. However, the farther you get from the equator, the
less direct the correlation.
There may be some La
Niña-ish effects next fall in the Cooks, but most
scientists would tell you at this point that it's only an
educated guess. If you'll accept that warning, then I can
guess that perhaps it will be rainier than normal there in
September. But probably not enough to change your plans.
Question:
Just wondering, haven't seen a mention of it, is there a
crack in the crust under the ocean that is warming the
waters? The heat runs up against S. America and has no where
to go, so it builds up? I can't exactly think of an example
but the closest I can come is the lava escaping at the edge
of one of the Hawaiian volcanoes. If you have an address
that can answer this question it would be much appreciated.
Thanx.
(name witheld by request)
Response:
You'd be surprised at how many people are interested in that
question. In fact, I've asked Billy Kessler, the
oceanographer whose wisdom we present in our
Frequently Asked Questions section,
to respond, and you will find
a detailed answer
there.
In the meantime, I can tell you there is a
crack in the crust under the ocean. In the middle of the
Atlantic and the Pacific, cracks called mid-ocean spreading
zones create ridges thousands of miles long that look almost
like the seams on a baseball, wrapping right around the
Earth, if you look at a map of the ocean bottoms. At these
cracks, the Earth spews up fresh lava from the mantle below,
and this hardens into new seafloor rock, pushing the
existing rock west and east as it shoves its way in. This
rock moves (at about the speed your fingernails grow) for
hundreds of millions of years, travelling thousands of
miles, until it finally is pushed into trenches near the
coasts of the continents, to descend back into the Earth,
and be heated all over again. In the Pacific these trenches
form the so-called "Rim of Fire" because volcanoes and
earthquakes frequently occur near them. Scientists call the
study of these phenomena "plate tectonics." For more on this
subject, try "The Restless Earth," by Nigel Calder.
Scientists have calculated how much heat is transferred to
the oceans from volcanoes, and it is
considerable—enough to make changes in the ocean's
circulation and also in its chemistry. But because the heat
is released under miles of water, into the thick cold layer
at the bottom, the effects are diffuse, and do not produce
sharp changes. The ocean, so to speak, only notices the
volcanic heat slowly.
El Niño, on the other
hand, is driven by solar energy, and the amount of energy
involved is almost beyond imagination. See
Global Weather Machine
for an idea of how much energy we're talking about. Also,
this heat is concentrated in a thin top layer (a couple of
hundred feet deep) on the ocean's surface. Here, the energy
can be quickly transferred to the atmosphere. This high
reactivity is intimately involved in the mechanics of El
Niño.
Question:
My husband and I will be taking a cruise leaving March 1
going to Western Caribbean (Grand Cayman, Cuzumel, Mexico).
Can you please give me your opinion on how the weather will
be in these places during that week? Will the ocean over
there be rough and rocky or will I never know the
difference? Help me if you can.
Thank you,
Rosemarie
Rosemarie Henderson, NC
Response:
Someone else asked recently about Aruba,
and the answer given there will likely suffice for you as
well. In short, ocean roughness (or storminess) will not be
much of an issue; you may see more variability than normal
(it might be cloudier or rain more than usual), but you
should get plenty of sunny days as well. If you were going
to the other side of Mexico, say Cabo San Lucas, then you
might have some problems because of the southerly trend in
the jet stream lately, the same culprit behind the current
drenching of southern California.
Question:
Your coverage of El Niño is quite extensive and very
interesting. One area I am finding difficult researching is
the progress of El Niño and how it has compared with
earlier forecasts. I have read that its impact should begin
weakening mid 1998, but have not seen any confirmation on
this. I am most interested as to the effect El Niño
will have on the northeast United States during the summer
months. Any information regarding the above would be
appreciated. Thanks for providing such a great site on this
exciting topic.
Rich DelMonte Weymounth, MA
Response:
First, thanks for your enthusiasm. Second, good news:
there's a lot of info available on how this El Niño
stacks up compared to others. Briefly, this is a record
breaker in almost every way.
Take a look at
this chart in Mapping El Niño;
it's an animation of the intensity of four different El
Niños, including this year's, and you can see for
yourself how they compare. In short, this El Niño
started earlier, peaked earlier, sustained its peak longer,
and developed a total energy content higher than any other
measured El Niño. Most El Niños start weakening in
the last two months of the year; this one kept growing right
up until the end of December. Although it is weakening right
now, and will stop making most of its mischief within
another couple of months, this El Niño has demonstrated
remarkable staying power. Some people mistakenly thought it
was washed up when it didn't produce drastic effects in
California during January; that thinking has now changed
with February's onslaught of storms. Peru has also been
devastated recently, with catastrophic flooding having
killed dozens of people.
Although this has been a
record-breaker, remember, human records of El Niño
don't go very far back; reliable and widespread weather
records have only been kept since the beginning of the 19th
century. Other records from nature herself suggest that
every 500 years or so we get a "Super El Niño." See
El Niño's Reach through Time
for more on the natural record.
As far as what El
Niño portends for the US this summer, others have asked
similar questions, and it will be worthwhile to read some of
the earlier mail here on that subject. In short, some
scientists feel we may have a hot, dry summer in the middle
and eastern parts of the US, although the evidence for such
a prediction is far from conclusive.
Question:
I would like to know what predictions were made worldwide
based on this 1997/98 El Niño, and what has actually
happened. I am doing this for a science project, and any
information you can give me or guidance to other sites would
be appreciated. Thank you in advance for your assistance.
Michael Williamson Franklin, VA
Response:
There was no shortage of predictions about El Niño's
effects this past year, ranging from the thought provoking
to the ludicrous. The science of prediction is improving at
breakneck speed, but it still has a long way to go; it
relies on models and theories that take into account what
has happened in the past, and then tries to integrate them
with current conditions. This is a HUGE computing task, and
even the most powerful supercomputers have trouble working
in enough detail to make the predictions better. That much
said, predictions of the major effects this year have been
remarkably accurate. When you are dealing with
probabilities, such as "an 80 percent chance of decreased
rainfall in southern Africa," it's tough to know how the
prediction will play out on a smaller, local scale. Maybe
part of southern Africa is dry as a bone, while other parts
are only a little drier than usual—predictions may be
way off for some places, and right on the money for others.
But when you look at the big picture, then the probabilities
are pretty useful. In general, predictions for dryness in
the western Pacific, greatly increased rainfall in the
eastern Pacific, and abnormalities elsewhere, such as in
North America and Africa, have been borne out. Check out the
interactive map in
the El Niño's Reach section of this Web site for an
overview. And if you need more info, several of the NOAA Web
sites listed in our
resources section
will have what you need.
(previous set of questions & responses)
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