So what is an el nino? Essay

This essay has a total of 3123 words and 17 pages.

So what is an el nino?

So What is an El Nino, Anyway?
A non-technical description

An El Nino is a temporary change in the climate of the Pacific ocean, in the region around
the equator. You can see its effects in both the ocean and atmosphere, generally in
Northern Hemisphere winter. Typically, the ocean surface warms up by a few degrees
celsius. At the same time, the place where hefty thunderstorms occur on the equator moves
eastward. Although those might seem like small differences, it nevertheless can have big
effects on the world's climate.

o What causes it?
o What makes it stop growing?
o What effects does it have?
o How long does it last?
o How often do we get them?
o How well can we predict El Nino?
o A more technical explanation

What causes it?
Usually, the wind blows strongly from east to west along the equator in the Pacific. This
actually piles up water (about half a meter's worth) in the western part of the Pacific.
In the eastern part, deeper water (which is colder than the sun-warmed surface water) gets
pulled up from below to replace the water pushed west. So, the normal situation is warm
water (about 30 C) in the west, cold (about 22 C) in the east.

In an El Nino, the winds pushing that water around get weaker. As a result, some of the
warm water piled up in the west slumps back down to the east, and not as much cold water
gets pulled up from below. Both these tend to make the water in the eastern Pacific
warmer, which is one of the hallmarks of an El Nino.

But it doesn't stop there. The warmer ocean then affects the winds--it makes the winds
weaker! So if the winds get weaker, then the ocean gets warmer, which makes the winds get
weaker, which makes the ocean get warmer ... this is called a positive feedback, and is
what makes an El Nino grow.

Back to top

So what makes it stop growing?
The ocean is full of waves, but you might not know how many kinds of waves there are.
There's one called a Rossby wave that is quite unlike the waves you see when you visit the
beach. It's more like a distant cousin to a tidal wave. The difference is that a tidal
wave goes very quickly, with all the water moving pretty much in the same direction. In a
Rossby wave, the upper part of the ocean, say the top 100 meters or so, will be lesirely
sliding one way, while the lower part, starting at 100 meters and going on down, will be
slowly moving the other way. After a while they switch directions. Everything happens very
slowly and inside the ocean, and you can't even see them on the surface. These things are
so slow, they can take months or years to cross the oceans. If you had the patience to sit
there while one was going by, you'd hardly notice it; the water would be moving 100 times
slower than walking speed. But they are large, hundreds or thousands of kilometers in
length (not height! Remember, you can hardly see them on the surface), so they can have an
effect on things. Another wave you rarely hear about is called a Kelvin wave, and it has
some characteristics in common with Rossby waves, but is somewhat faster and can only
exist close to the equator (say, within about 5 degrees of latitude around the equator).

El Ninos often start with a Kelvin wave propagating from the western Pacific over towards
South America. Perhaps you saw, on the TV news, the movie (produced by JPL) for the El
Nino of 1997/98? It showed a whitish blob (indicating a sea level some centimeters higher
than usual) moving along the equator from Australia to South America. That's one of the
hallmarks of a Kelvin wave, the early part of the El Nino process.

When an El Nino gets going in the middle or eastern part of the Pacific, it creates Rossby
waves that drift slowly towards southeast Asia. After several months of travelling, they
finally get near the coast and reflect back. The changes in interior ocean temperature
that these waves carry with it "cancel out" the original temperature changes that made the
El Nino in the first place. I'm being deliberately vague here becuase it's complicated;
look at the "For Further Reading" link or the "More Technical Explanation" link for more
information. The main point is that it shuts off when the these funny interior-ocean waves
travel all the way over to the coast of Asia, get reflected, and travel back, a process
that can take many months.

Back to top

What effects does it have?
A strong El Nino is often associated with wet winters over the southeastern US, as well as
drought in Indonesia and Australia. Keep in mind that you aren't guaranteed these effects
even though there is an El Nino going on; but the El Nino does make these effects more
likely to happen.

Back to top

How long does it last?
A strong El Nino can last a year or more before conditions return to normal. If you read
the bit above about Rossby and Kelvin waves (you did, didn't you?) then you know that it
lasts more or less as long as it takes the interior-ocean waves to travel all the way over
to the coast of Asia, get reflected, and travel back. You can also look at the Historical
El Nino section, which has a plot showing the last 30 years of El Ninos, and judge for
yourself.

Back to top

How often do we get them?
El Ninos happen irregularly, but if you want to impress people at cocktail parties, you
might mention that we usually get one every three to seven years. Note the word "usually":
sometimes they turn up more frequently, sometimes less. You can also look at the
Historical El Nino section, which has a plot showing the last 30 years of El Ninos, and
judge for yourself (deja vu).

Back to top

How well can we predict El Nino?
On average, complex computer models designed to predict El Nino can successfully do so 12
to 18 months in advance. However, it seems to vary by episode; sometimes El Ninos are
predicted quite well, with plenty of advance notice from the models, while other times
they are predicted poorly, with the models not picking them up until the El Nino has
already started. Trying to fix up the models is one of our research topics here at
Scripps.

Back to top

This isn't much of an explanation.
A more technical explanation, complete with nifty graphics, has been created by the people
at NOAA's Pacific Marine Environmental Laboratory. Check that out, or look at the "For
Further Reading" link for written material.

/////////////
http://meteora.ucsd.edu/pierce/elnino/whatis.html
Last modified: 25 June 1997
Copyright © 2000 David W. Pierce. All rights reserved.
///////////////


El Nino
a warm current of water
El Nino (Spanish name for the male child), initially referred to a weak, warm current
appearing annually around Christmas time along the coast of Ecuador and Peru and lasting
only a few weeks to a month or more. Every three to seven years, an El Nino event may last
for many months, having significant economic and atmospheric consequences worldwide.
During the past forty years, ten of these major El Nino events have been recorded, the
worst of which occurred in 1997-1998. Previous to this, the El Nino event in 1982-1983 was
the strongest. Some of the El Nino events have persisted more than one year.

El Nino Years
1902-1903 1905-1906 1911-1912 1914-1915
1918-1919 1923-1924 1925-1926 1930-1931
1932-1933 1939-1940 1941-1942 1951-1952
1953-1954 1957-1958 1965-1966 1969-1970
1972-1973 1976-1977 1982-1983 1986-1987
1991-1992 1994-1995 1997-1998

Selected text from: CPC ENSO Main Page
In the tropical Pacific, trade winds generally drive the surface waters westward. The
surface water becomes progressively warmer going westward because of its longer exposure
to solar heating. El Nino is observed when the easterly trade winds weaken, allowing
warmer waters of the western Pacific to migrate eastward and eventually reach the South
American Coast (shown in orange). The cool nutrient-rich sea water normally found along
the coast of Peru is replaced by warmer water depleted of nutrients, resulting in a
dramatic reduction in marine fish and plant life.


Animation by: Shao
In contrast to El Nino, La Nina (female child) refers to an anomaly of unusually cold sea
surface temperatures found in the eastern tropical Pacific. La Nina occurs roughly half as
often as El Nino.

La Nina Years
1904-1905 1909-1910 1910-1911 1915-1916
1917-1918 1924-1925 1928-1929 1938-1939
1950-1951 1955-1956 1956-1957 1964-1965
1970-1971 1971-1972 1973-1974 1975-1976
1988-1989 1995-1996


1997-1998 El Nino
the most recent event
The most recent El Nino event began in the spring months of 1997. Instrumentation placed
on Buoys in the Pacific Ocean after the 1982-1983 El Nino began recording abnormally high
temperatures off the coast of Peru. Over the next couple of months, these strength of
these anomalies grew. The anomalies grew so large by October 1997 that this El Nino had
already become the strongest in the 50 years of accurate data gathering.

The image below displays the Sea Surface Temperature (SST) Anomalies in degrees Celsius
for the middle of September, 1997. By this time, the classic El Nino pattern has almost
fully ripened, with maxima above 4 degrees Celsius.


Continues for 9 more pages >>




  • A history of marine science
    A history of marine science Morris 1 Rich Morris OCE 1001 Sept. 09, 2000 Ch.2 A History of Marine Science The early history of marine science started about 11,000 years ago. Nomads began voyaging into east and central Europe, and across the plains of central Asia. They journeyed to the shores of northeastern Asia and crossed the Bering Sea into North America and South America. Most traveled on foot except for those who were talented in raft building or navigation. Any coastal culture with these
  • Devils lake
    devils lake Dramatic Fluctuations of Devils Lake, North Dakota: Climate Connections and Forecasts Connely K. Baldwin and Upmanu Lall Utah Water Research Laboratory, Utah State University, Logan, UT 84322-8200 Introduction The recent (1992-date) record rise in the level of the Devils Lake, North Dakota, has led to a number of questions as to the nature of regional and global climate variability, and the utility of existing methods for forecasting lake levels and assessing the associated flood ris
  • Plate tectonics
    plate tectonics Now Showing Matches 1 To 19 Field Guide to Geology A 6 page book report on "The Field Guide to Geology" by David Lambert. Lambert is known for his clear and unique style of cataloging information so that laymen can readily understand the subject. This book is no exception to that rule. It is a very clear and concise introduction to the world of geology, written in easy to understand language. He covers subjects such as the earth\'s crust, volcanoes, rocks in general, deformed and
  • The effect of chrysler
    the effect of chrysler TERM PAPER EXAMPLES ! Enter the NEW Term Paper Help Site HERE and SKIP the Other ads! -------------------------------------------------------------------------------- Enter Your Term Paper Topic Here: If You Get No Reponse, Press STOP & Then Click This Link ! -------------------------------------------------------------------------------- -or- Select Your ESSAY Topic Below: *** Essays - Topics *** Accounting & Finance - Personal Finance - Money & Banking - Corporate Financ
  • Declining Clarity of a Jewell Exploring Lake Tahoe
    Declining Clarity of a Jewell Exploring Lake Tahoe DECLINING CLARITY OF A JEWEL - EXPLORING LAKE TAHOE BY LESLIE WATSON ELLINGSON APRIL 20, 2000 TABLE OF CONTENTS Lake Tahoe An Introduction Page 2 Lake Tahoe -- History Page 3 Figure One -- Tahoe Region Map Page 3A Lake Clarity -- Introdution to Causes Page 5 Figure Two -- Secci Depth Chart Page 6A Soil Erosion Page 7 Figure Three -- Population Graph Page 7A Air Quality Page 8 Water Inflow and Algae Growth Page 9 Figure Four -- Water Cycle Flow C
  • Three branches of science
    three branches of science Three Branches of Science Andrew Rambo Ms. Gardener 10th Grade Biology September 11, 2000 Science is such a wide area that it is divided into branches. Biology, chemistry and geology are three of these branches. Each branch of science are very different. They use many of the same techniques in the study of the materials in their area of science, but are very different materials. Biology is the study of life and living things. The French naturalist, Jean Baptiste, introd
  • Visit to earth observatory
    visit to earth observatory Every year the Lamont Doherty Earth Observatory holds an open house in which scientists share their studies and really let the public see what and how they do what they do. Scientists at this research center are working together studying different fields of the Geologic sciences ranging from Oceanography, Geochemistry, Seismology, and even Marine Biology share their findings with the public. This year like every other year, they set up deferent exhibits and share the
  • Christianity in a Postmodern World
    Christianity in a Postmodern World Christian Belief in a Postmodern World: The Full Wealth of Conviction Others have tried to do what Diogenes Allen, Professor of Philosophy at Princeton Theological Seminary, does in his book but none with his breadth or effectiveness. That is, others have attempted to exploit for theism\'s benefit the hard times now befalling the modern world\'s emphasis on scientific reasoning and pure rationality, which for quite a while had placed Christianity (and religious
  • Ocean Environment
    Ocean Environment Ocean Environment The sea is the most obvious feature of the earth\'s surface. Approximately seventy percent of this surface is covered by water, in one way or another. Beneath this water are the familiar sands of the beaches, bottoms of bays, and the inshore ocean. Farther offshore this water covers an amazing submarine topography of underwater canyons, trenches, mountains, and plains. Unlike the continents, which are physically separated from one another, the oceans are conti
  • Dramatic Fluctuations Of Devils Lake, ND
    Dramatic Fluctuations Of Devils Lake, ND Dramatic Fluctuations of Devils Lake, North Dakota: Climate Connections and Forecasts Connely K. Baldwin and Upmanu Lall Utah Water Research Laboratory, Utah State University, Logan, UT 84322-8200 Introduction The recent (1992-date) record rise in the level of the Devils Lake, North Dakota, has led to a number of questions as to the nature of regional and global climate variability, and the utility of existing methods for forecasting lake levels and asses
  • Accountants and Auditors
    mr Accountants and Auditors There are 4 types of accountants: Public Accountants, Managerial Accountants, Internal Auditors, and Government Accountants. Public Accountants work for public accounting companies, Managerial Accountants keep track of company\'s accounts, Internal Auditors check the accuracy of company\'s accounts and look for evidence of theft, and Government Accountants and Auditors keep track of the government\'s accounts and auditing. Accountants and Auditors manage taxes, accoun