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We will remember for
some time the record storm that buried the front range in
several feet of snow in late October. On one hand, cities were
paralyzed. Roads were closed, businesses shut down, and a state
of emergency declared. On the other hand, cities came to life.
Neighbors helped neighbors dig out their homes, people with
four-wheel drives helped take needed medical personnel to
hospitals, and search crews found and saved numerous stranded
motorists. Uplifting stories of good deeds and heroic rescues
dominated the usually depressing newscasts.
Such an unusual storm had to have a cause, and El Nino was quick
to get the blame. That made sense; after all we have certainly
been hearing a lot about El Nino's power to impact our weather
lately. Immediately after the front range storm, the Denver Post
ran a headline claiming El Nino had socked its first punch for
the winter. But the Rocky Mountain News ran a headline citing
experts as claiming El Nino was not to blame for the storm. More
important than who scooped whom (the News was more accurate in
this instance), this illustration shows that El Nino is perhaps
the most talked about yet least understood weather phenomenon of
recent times.
What
Is El Nino?
For many years, Peruvians have noticed a warming of the waters
in the Eastern Pacific about every four years. Because the
warming often begins in late December, it was given the name El
Nino, in this case, "the Christ child." Meteorologists, knowing
of its existence but long believing its effects were only local,
pretty much ignored El Nino and concentrated their studies on
many other weather phenomena. One such phenomenon was the
Southern Oscillation.
The Connection Down Under
The Southern Oscillation (SO for short) was first documented in
the 1930s. Sir Albert Walker noticed that when the air pressure
was high in Darwin, Australia, it was low in Tahiti (an island
in the South Pacific), and vice versa. He also noticed that the
air pressure seemed to change, or oscillate, in a fairly regular
pattern. But it wasn't until 1969 that a direct link between El
Nino and the SO was first noticed. Only in the past twenty years
has there been a focus on these connected events which likely
effect the climate and weather over much of the earth.
Not An Only Child
When the air pressure is high in Darwin, an El Nino is present
in the Eastern Pacific. But when the air pressure is low in
Darwin, the waters of the Peruvian coast cool well below normal.
This cooling has been called La Nina, the Sister. A La Nina
usually occurs between each El Nino.
It is this Southern Oscillation and El Nino/La Nina cycle that
affects climate in many parts of the world. To avoid cumbersome
names (or from a lack of understanding), the media generally
mentions only El Nino when referring to this larger phenomenon.
Effects Of El Nino
The effects of El Nino are very difficult to predict. One reason
is that El Ninos vary in many ways. No two El Ninos give the
same results. California has experienced very wet conditions in
some El Nino years and drought during others. To further
complicate things, other phenomena occur (such as jet stream
movement) that also affect weather and climate. Making local
predictions based on El Nino is seldom successful.
Here
At Home
All weather is the result of a variety of conditions at a given
time. If we knew every variable involved, the impact each
variable had, how the variables interacted, and could measure
each variable precisely, then we might be able to consistently
and accurately predict weather anywhere. El Nino, in the large
picture, definitely impacts weather and climate. But we cannot
accurately say that our weather this winter will be due to El
Nino. According to Michael Glantz, one of the nation's leading
experts on El Nino, specific local weather events cannot be
blamed on nor denied cause by El Nino.
The accompanying graph shows average valley winter temperatures
and El Nino/La Nina events for a forty year period. While
winters colder than average have occurred in the valley during
recent El Nino years, there is not a strong, predictable
relationship between El Nino and our average winter
temperatures. The movement of the jet stream more likely has a
stronger correlation to weather in the San Luis Valley.
El
Nino Is Here!
While we may not be able to directly attribute our daily weather
to El Nino, we can certainly document that El Nino has indeed
invaded Colorado. Pick up a Sunday newspaper and count the "El
Nino Sale" advertisements (better hurry and buy that four-wheel
drive). Listen to the newscast and count how many times you hear
"El Nino" mentioned by someone other than the weather anchor.
Try to find someone, anyone, who has not heard of El Nino. El
Nino has come to stay (and, apparently, left his sister behind)!
The
Future Of El Nino
Although a few decades ago El Nino was left untouched by
scientists, meteorologists around the world are now devoting
much time and energy to unraveling the mysteries of this
tropical phenomenon. In time, as data is gathered and analyzed,
we might be better able to understand and predict the global
effects of El Nino. The economic and humanitarian benefits of
being better able to predict drought or flooding well in advance
are obvious. In the meantime, it will be interesting to see how
our perception of El Nino changes with time. Although it is
mainly the fear of the cold that keeps El Nino in our minds,
perhaps in some small way, especially this time of year, we are
attracted to the irresistible warmth of a child.
©
2006 Dirk Oden
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