Certain terms we need to keep in mind in this course for the rest of the
school year. These terms are listed below. A quiz on these terms will be
given Friday.
1) Observation - the perception of the environment by our senses. There are
five senses - taste, sight, touch, smell, and hearing. We observe pollution
in the environment, we observe when the environment is clean. We can
determine a safe environment or a dangerous environment.
2) Instrument - a human made device that extends the senses beyond their
natural limits. These are used in the lab setting through microscopes,
telescopes, rulers, X-rays, calculators, etc. These are important to
increase our understanding of the environment.
3) Inference - an interpretation of the environment without actually seeing
it. We have never been to the center of the Earth, yet we infer it to be
nickel and iron because we have observed 90% of all asteroids to be made of
these.
4) Classification - grouping observations and inferences based upon similar
characteristics. The seven kingdoms in biology are an example because they
help us to relate a known observation to an unknown one.
5) Measurement - expressing an observation to a greater degree or with
better accuracy. Comparing two objects as bigger or smaller than each other
is an example. Expressing the length or weight of an object in numbers is
another example.
6) Mass - amount of matter in an object. This is not the weight. Metal is
more massive than air. A giant helium balloon will float while a penny will
sink because the penny is more massive.
7) Volume - the amount of space occupied by an object. The bigger something
is, the more volume it has. Think of cars, toys, and houses.
8) Percent deviation - expressing a mistake in numbers. Because we are
human, we make mistakes. How big our mistake is is called a percent
deviation. The formula is:
Real answer - Your answer
-------------------------------- x 100%
Real answer
If you calculate mass to be 64 grams and it really is 66 grams, the percent
deviation is:
66 - 64
-------- x 100%
66
3.03%
9) Density - concentration of matter in an object occupying a certain amount
of space. The more volume, the smaller its density, and vice versa. The
formula is:
Mass/Density
If an object�s mass is 100 grams and its volume is 50 cubic centimeters, its
density is 100 grams/ 50 cubic centimeters, or 2 grams/cubic centimeter.
10) Change - when the environment�s characteristics change over time. It
could be cyclical and predictable (seasons, eclipses) or noncyclical and
unpredictable (storms). Change could occur rather quickly (tornadoes) or
over many years (global warming). The formula is:
Change in field value
-------------------------
Change in time
If it was 60 degrees this morning and now it is 70 degrees and if 5 hours
passed, the rate of change is:
70 - 60 degrees
---------
5 hours
or 2 degrees/hour.
11) Interface - the boundary between two different environments. Between the
land and the ocean is an interface because we move from solid material to
liquid water. The characteristics of both environments change.
12) Equilibrium - a state when the environment is balanced. Since Earth
changes constantly over time, the equilibrium changes. This is called a
dynamic equilibrium. More on this later.
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Natural resources are those materials and energy that we use from the
environment. The air we breathe, the water we drink, the food we use. Fossil
fuels, rocks, minerals are all considered natural resources.
Even though resources are important to our lives, not every one in the
world enjoys the existence of a given resource nor the same quantity of a
given resource. For example, not every nation is an oil producer. This has
led to Japan�s decision to practice imperialism at the start of World War
II, and this has led to the belief that the US invaded Iraq for its oil
because both Japan and the US are not blessed with oil needed to supply
their people. Even nations that have precious metals do not have the same
quantity of the metal. Gold is not found everywhere in the world, and it is
not found in the same quantity in the nations that do have it. Diamonds are
rare because so few nations can mine them.
Resource is another term for natural resource. Therefore, anything from
nature used by people is a resource.
Renewable resources are those materials that are rather easy to replace
when used. These include the air we breathe, the water we drink, the food
supplied by nature, the wind currents, the energy from the sun, etc. On the
other hand, nonrenewable resources are those materials not easily replaced
by nature because they take millions of years to reproduce. These include
any fossil fuel, soil, metals, minerals, gems, etc.
The way we work to preserve our resources is called conservation.
Replanting trees, crop rotation, developing alternative energy resources,
limiting the use of resources, treating the environment with increased
respect are all conservation methods that we need to practice.
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Pollution is a condition of the environment in which living organisms are
affected negatively. High concentrations of pollutants destroys the
environment over time. For example, smoke from factories, exhaust from
automobiles, CFCs from hair sprays all erode the sidewalks and bricks over
time.
There are several causes of pollution. Most causes of pollution are the
result of the Industrial Revolution. Some of these causes were mentioned in
the above paragraph. Other causes are natural - volcanic eruptions,
electromagnetic energy (radiation), nuclear waste, bacteria, sound, light.
Despite the existence of pollution, there are measures that we can take as
stewards of the environment to reduce or prevent the existence of pollution.
One such method is crop rotation, varying the field in which we plant
certain crops. Another measure is to use sun screen to block the sun�s
harmful ultraviolet rays from reaching our skin. We can develop safer
containers to dump nuclear waste. We can practice taking medicine and
improving our medical knowledge. There are so many other preventive measures
that we can practice. Can you think of any others?
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Every place on Earth is unique in its appearance and location. New York City
does not have an identical location anywhere else. On a map we could see
only NYC in its place, not Boston or Santa Fe. How de we know where NYC is?
We use a locating system known as the latitude-longitude system. What does
this mean?
Latitude is a horizontal line running east to west. These lines are also
called parallels because they never touch one another. These lines measure
distance north and south from the Equator. The Equator is an important line
of latitude at 0 degrees. This is the middle of Earth horizontally. Other
important lines of latitude are the North Pole at 90 degrees North, the
South Pole at 90 degrees South, the Tropic of Cancer at 23.5 degrees North,
the Tropic of Capricorn at 23.5 degrees South, the Arctic Circle at 66.5
degrees North, and the Antarctic Circle at 66.5 degrees South. When we
discuss astronomy, we will discuss why these are important. Since all
parallels never touch, we can say that there are 70 miles between each
degree of latitude.
Longitude is a vertical line running north to south. These lines are also
called meridians. Unlike parallels, these lines touch each other at the
poles. These lines measure distance east and west from the Prime Meridian.
The Prime Meridian is an important line of longitude at 0 degrees. This is
the middle of the Earth vertically. Another important line of longitude is
the International Date Line at 180 degrees. This line sits directly behind
the Prime Meridian. Since these lines touch each other, there is no set
distance between any two meridians because they are closer together at the
poles and further apart at the Equator.
We locate places using these two sets of lines by writing the latitude line
first and the longitude line second. For example, New York City is located
at 41 degrees North, 74 degrees West. Note the following:
1) We have latitude first, not second. IT IS WRONG TO SAY NYC IS LOCATED AT
74 DEGREES WEST, 41 DEGREES NORTH.
2) We must write the location after the number. 41 degrees, 74 degrees is
wrong!!! Is it 41 degrees North, 74 degrees West? 41 degrees North, 74
degrees East? 41 degrees South, 74 degrees West? 41 degrees South, 74
degrees East? IT IS VERY IMPORTANT TO WRITE THE DIRECTION DOWN SO THAT WE
KNOW WHERE TO LOOK ON A MAP!!!
One last point: The Equator divides the Earth into two halves, called
hemispheres. These two hemispheres are the Northern Hemisphere above the
Equator and the Southern Hemisphere below the Equator.
The Prime Meridian divides the Earth into two hemispheres also. These are
the Eastern Hemisphere to the right of the Prime Meridian and the Western
Hemisphere to the left of the Prime Meridian.
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Topographic maps, or contour maps, are maps to represent the elevation
(height) of various areas to give us an idea about an area�s physical
appearance. These maps give a bird�s eye view of an area. For example, I
have never been to the Grand Canyon, but I know what the terrain is like
based on pictures of the Grand Canyon. Before the invention of cameras,
though, people depended on topographic maps to gain a better perception
about an area�s physical appearance. How? There are certain rules that are
universal to creating topographic maps. No matter where a person is from,
these rules are the same. It is the same as math. No matter where a person
comes from 2 + 2 = 4. Therefore, what are these rules?
1) Topographic maps represent the elevation of an area. This elevation is
represented by contour lines. These lines are usually closed. These lines
are brown and only brown. If these are not brown, they are not contour
lines. Every point on this line has the same elevation. Why? The answer is
simple. In geometry, you learned that two points make up a line. These
points must have certain things in common to make up the line. In this case,
they have the same height. These lines never touch.
2) Any water on a map is blue. If there is a lake or a river or a sea, it
MUST be blue. When rivers are drawn on a map, the water must flow downhill,
or from higher elevation to lower elevation. How do we see this on a map?
The contour lines bend when crossing a river. The lines bend upstream, or
they POINT uphill. The river flows in the OPPOSITE DIRECTION that the lines
point.
3) Any plant life or forest or wooded area is green and only green. They
cannot be brown or gray. These colors represent other things.
4) Every fifth contour line is a dark brown. Only these lines are labeled
with an elevation. These lines are called index contours. Why do we use
index contours? Many times a contour map has dozens of lines. This becomes
too confusing if all lines are labeled. Therefore, we only label every fifth
line.
5) If lines are close together, we say that the slope in the area is steep.
This means that there is a sharp hill in the area that is difficult to climb.
6) If lines are further apart, we say that the slope is gentle. This means
that the area climbs rather slowly, as in the Midwest.
7) All cliffs are represented by lines that touch each other. This is the
only exception to lines not touching. Why do we do this? At a cliff there is
a straight drop to the bottom. All elevations meet here.
8) Hilltops are represented by a series of smaller circles somewhere on the
map.
9) Specific heights are represented by an �X�, called a spot elevation.
These are used for places of interest, such as landmarks or historical
sights.
10) To represent a drop in height, we use depression contour lines, which
are brown. These lines have teeth inside of them called hash marks.
11) All contour lines have the same interval between them when labeling
them. This interval is the contour interval. Every line on the map has the
same difference between them in height. The most common intervals are 10,
20, 50, 100 meters.
12) Depression contours represent drops in elevation.
Now that we know how to illustrate a contour map, we can calculate the
gradient (slope) of the area using the following formula:
Change in height
---------------------
Change in distance
If we see that a location climbs 2 meters over the course of 15 kilometers,
the gradient is:
2 � 0 meters
---------------
15 � 0 kilometers
OR,
0.13 meters/kilometer
If an area rises from 15 meters to 20 meters in 2 kilometers, the gradient
is:
20 � 15 meters
------------------
2 kilometers
OR,
5 meters/2 kilometers = 2.5 meters/kilometer
Which one is steep and which is gentle?
The first is gentle, and the second is steep.
Once we know how to create contour maps, we can create a map profile
following these rules:
1) Draw dotted lines from each line on the contour map to a space beneath.
Be sure to include both sides of the same line, all lines, and keep all
dotted lines even with the map above.
2) Using the vertical axis, label all heights of the contour map and put a
dot on each dotted line at the height for the given line.
3) Connect all dots. (SEE NOTEBOOK FOR EXAMPLE)
Map profiles give us a side view of a given location.
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Astronomy
Astronomy is the study of space and all celestial objects in it. A celestial
object is anything that floats in space and includes stars, planets,
meteors, comets, dust, and junk. One of the most important questions in
astronomy is: When and how did the universe begin? The universe is space.
Astronomers have proposed the Big Bang Theory to answer the question about
the universe�s origins. The Big Bang Theory states that about 20 billion to
30 billion years ago a cosmic cloud of extremely hot gas existed in a void.
This cloud was about the size of the Milky Way Galaxy. It rotated around
itself, creating gravity. This force of gravity began pulling the outer
portions of the cloud in on itself. By pulling the outside in, the cloud
began shrinking. This shrinking increased the temperature in the core of the
cloud to critical levels. When the temperature could not be contained
anymore, a giant explosion occurred which sent chunks of the cloud spiraling
outward in all directions. The pieces from the outside of the cloud moved
the slowest and are now the closest objects to Earth as a result while the
pieces from the inside moved the fastest and are the objects in space that
are furthest away. Every time astronomers detect radio waves that are
another billion light years from us, the Big Bang Theory is updated because
that is another billion years that the explosion occurred. As time passed,
the elements in the cloud cooled into larger elements until solids formed.
More on this later.
What evidence do we have about this? Astronomers have equipment in space
and on the ground that detects radio waves emitted in space. Why is this
important? Everything in space emits radio waves. The weaker these waves
are, the further away an object is. This is proof that objects are moving
away from us. Another piece of evidence that astronomers use is the
collection of energy waves emitted by stars. If stars emit short wave
radiation, they are nearby, but if they emit long wave radiation, they are
far away. Yet, a third piece of evidence that astronomers use is the fact
that 90% of all meteors are composed of iron &/or nickel. This is important
because these elements are part of the genetic code of the universe. The
only way for most of anything to have elements in common is if they have the
same parents, or the same beginning.
A second common question in astronomy is whether or not the universe is
expanding or contracting. Astronomers are in disagreement over this
question. Some say that the universe is expanding, and cite the long wave
radiation that is detected on a daily basis as evidence. Yet, there are
those that say the universe is contracting and cite the short wave radiation
as evidence. These two schools of thought are the open universe (expanding)
and the closed universe (contracting) schools of thought. No matter which
school you accept, they both use the electromagnetic spectrum to support
their position.
The electromagnetic spectrum is the collection of all energy in the
universe. It consists of three pieces. The first piece is the short wave
radiation (gamma rays, x-rays, and ultraviolet waves). The second piece is
visible light (red, orange, yellow, green, blue, indigo, and violet). This
is a small piece of the spectrum, and it is the only piece we can see. The
third piece is the long wave radiation (infrared waves, microwaves, and
radio waves).
Members of the open universe school use the third piece as evidence for
expansion while members of the closed universe school use the first piece as
evidence for contraction. How do they collect this evidence? A special
telescope called a spectroscope is used to gather the light of stars in the
sky. The elements in the star emit certain colors that spread out on a sheet
of paper that has all the visible light on it. The arrangement of color on
the paper tells the astronomers what element is in the star as well as if
the star is getting closer or further away. How? If the arrangement is
toward red on the paper, the star is moving away and is evidence for a red
shift. These stars emit long wave radiation. If the arrangement of color is
near the blue end of the paper, it is evidence for a blue shift. These stars
emit short wave radiation. If the arrangement is in the middle of the paper,
there is no shift and is inconclusive. These shifts are referred to as a
Doppler Effect.
The arrangement of the electromagnetic spectrum is in the Earth Science
Reference Tables on page 14.
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The universe is everything around us and everything beyond what we can see.
Space is the universe like Cathedral is our school. Yet, the universe can be
broken down into components like the school can be broken into components.
We can divide the universe into clusters called galaxies like we can break
the school down into clusters known as Seniors, Juniors, Sophomores,
Freshmen. Each galaxy can be broken down into solar systems like each
academic year can be broken down into different classes. Each solar system
can be broken down into its individual parts � the planets � like each class
can be broken down into its individual pieces � the students. Collectively,
these form the universe. We can never study astronomy by studying the
universe because it is too big to comprehend. Instead, we study the
individual pieces. Let�s study these pieces.
What is a galaxy? A galaxy is a collection of billions of stars, dust, gas,
and solid material held together by the force of gravity created from the
rotation of the galaxy. The Milky Way Galaxy � ours � contains several
hundred billion stars alone. There are several hundred billion galaxies that
we are aware of!!! Yet, each galaxy has its own unique characteristics.
There are three different types of galaxies. The first is a spiral galaxy.
Approximately 90% of all galaxies are spiral. These are round in nature with
tiny arms reaching into space. The Earth is located on one of these arms.
What is at the center of the Milky Way Galaxy? No one knows for sure, but
many people believe it is a black hole. Look at a picture of it. Do you see
stars there?
The second type of galaxy is an elliptical galaxy. These galaxies make up
about 8% of all known galaxies. These are shaped like a football primarily.
Stars are clustered in the middle with some panning out.
The third type of galaxy is an irregular galaxy. These galaxies comprise
approximately 2% of all known galaxies. These do not have a definite shape.
Hence, they are irregular.
Every galaxy is composed of stars. Stars are large balls of gas held
together by gravity that produces a very large amount of energy. How do
galaxies and stars produce gravity? These celestial objects rotate around
their own axis much like the Earth rotates on its axis. This rotation
creates gravity that holds all the elements of a galaxy or star together.
Stars rotate much faster than Earth does, producing much more energy than
Earth ever will. The size of the star determines how much energy is produced
and how bright it will shine. The amount of energy will also determine a
star�s color. The different types of stars include super giants, giants,
white dwarfs, black dwarfs, blue stars, red stars, yellow stars, and white
stars. Look at the Earth Science Reference Tables (page 15) � Luminosity and
Temperature of Stars Chart. Blue stars have a temperature of about 12,000
degrees C or higher and are huge stars. These are the brightest stars in the
night sky, yet they are billions of light years away. White stars are
anywhere from 7,500 degrees C to 12,000 degrees C and are small. These are
the second brightest stars in the sky. Blue super giants formed from large
pockets of gas and produce a great deal of energy while white dwarfs formed
from small pockets of gas and produce a great deal of energy. Yellow stars,
like our Sun, are anywhere from 3,500 degrees C to 7,500 degrees C. These
started as either blue or white and have cooled off over time. Red stars are
the coolest (less than 3,500 degrees C) and are either super giants or
dwarfs, depending upon several factors that we will discuss later. Practice
reading this chart. Details on how to do so will be explained in class.
Stars create energy using nuclear fusion. Scientists on Earth have
discovered nuclear fission, splitting an atom. Nuclear fusion is combining
two atoms. This requires intense heat, found only in stars. Think about
welding two pieces of metal together with a blowtorch. This is the same
thing. Stars usually begin with hydrogen. The intense heat fuses two
hydrogen atoms to form a helium atom, which is bigger than hydrogen. As time
elapses, the helium fuses with more helium to create a larger atom, and so
on until all the energy is used up or until a solid is formed (usually iron
or nickel). If this happens, the star burns out. This is what will happen to
the Sun in about 5 billion years. Today, the Sun still has about half the
hydrogen it started with. The amount of energy makes the star burn brighter
or dimmer. Bright stars are young while dim stars are old. Therefore, blue
or white stars are young while red stars are old. All stars move from blue
to white to yellow to red. More on this later. The more energy in a star
means the hotter the star, which also determines its color. More energy =
brighter = hotter while less energy = dimmer = cooler.
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Just like a human being, a star goes through a series of stages referred to
as its life cycle. The amount of energy in a star is dependent upon the
stage that a given star is in, just as the amount of energy in a person
depends on what age group we are speaking about. Children have more energy
than teenagers who have more energy than adults who, in turn, have more
energy than elders. The same is true with stars. The life cycle of a star is
called the main sequence. 90% of all known stars are located in the main
sequence. This sequence is located on page 15 of the Earth Science Reference
Tables in the Temperature and Luminosity Chart.
All stars begin life as a nebula, which is a cloud of dust, gas, and ash
lingering in space. These nebulae have their origin in the Big Bang or from
stars that have exploded over time. Gravity causes these particles to
coalesce, or form a star by fusing together. As these particles fuse
together, they create friction between them. When the mass of these clouds
reaches the mass of Jupiter, their temperature starts rising, creating
nuclear fusion. Once nuclear fusion results, the cloud is referred to as a
star. This fusion is what makes the star shine. Now radiation can be emitted
into space.
The size of the nebula will determine the death of the star. Let�s begin
looking at the evolution of a small nebula. Our sun was created from a small
nebula about 5 billion years ago. Originally, our sun was a small blue star
because of the intense heat created from nuclear fusion. As more and more
hydrogen was fused into helium, the star expanded because of the high
temperatures. However, since more helium means less energy, it began to cool
off into a white star. This cooling process continues to this day, since the
sun is classified as a yellow star. It will continue to cool off as time
passes. Eventually, as bigger elements are created in the sun, it will
expand into a red giant. Once this stage is reached, the energy will cease
and it will collapse into itself, forming a white dwarf. The size of these
dwarfs is smaller than Earth. The surface temperature is hot because of its
size. White dwarfs do not shine as brightly in the sky because they are
cooling off. Once a white dwarf stops radiating energy, it dies; hence, a
black dwarf.
Stars with lots of mass � so called giants - are 10 to 100 times bigger
than the sun. These stars also begin life as nebulae � very big ones � and
are blue at first. As time continues, they cool off to white, then yellow,
and finally red. They also expand as they age. However, because of their
high mass, they explode in a nova. This nova does two things. First, it
creates another nebula for a future star to form. Second, it releases all of
its energy, leaving only very dense neutrons behind. Hence, a neutron star
is formed. These pulse over time, until all of its energy is utilized.
Stars with extremely high masses � so called super giants � are 100 to 1000
times the size of the sun. These form from massive nebulae and are blue at
first. They also cool off to white, then yellow, and then red. These explode
in a super nova event, leaving behind giant nebulae to form future stars.
These may also implode, forming a black hole. The gravitational field of a
black hole is so dense that no form of energy escapes.
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The star that is closest to Earth is called the sun. The Latin word for sun
is sol. Therefore, the family of the sun � those celestial objects that
orbit the sun � are referred to collectively as the solar system. Just as in
each of your families every one is different, so too in this family is every
one different. Some members are small, some are big, some are close by, some
are far away, some are interesting, some are dull, some are hot to be
around, and some are cold as ice.
The sun is the parent of this family. In fact, the sun is so big in
importance that it contains 99% of all the mass in the solar system. It is
about 5 billion years old, medium sized, yellow, main sequence, and has
thousands of satellites around it. These satellites are planets, asteroids,
moons, comets, and meteoroids.
Planets are the largest objects in the solar system and are solid. They are
spherical in shape. Based on radio waves detected from space, astronomers
have identified hundreds of planets floating in space around other stars.
More characteristics on planets tomorrow.
Asteroids are solid chunks of rock floating in the asteroid belt between
Mars and Jupiter mainly. Astronomers are not sure what the story on
asteroids is all about. The common theory is that they did not coalesce into
a planet at the formation of the solar system. Either that or they exploded
soon after formation. Most asteroids are 100 to 1000 kilometers in size. The
largest is Ceres. Their shapes vary and are not always easily defined. Most
are iron and/or nickel in composition, and they do not possess an
atmosphere.
Moons, or natural satellites, are spherical solids that orbit around
planets. Since they orbit around planets, they are smaller than the planets
they orbit. We are aware of dozens of moons in our solar system, mostly on
the outer realms of the solar system. The biggest one is Triton orbiting
Saturn. The Earth Science Reference Tables lists the number of moons per
planet.
Comets are rocks floating from one end of the solar system to the other.
Their orbits vary from 2.3 years to several thousand years. The most famous
one is Halley�s Comet (76 year orbit). When they approach the sun, the ice
around the rock melts, forming a tail. The nucleus of the comet is usually
iron with frozen water and methane gas. They could be anywhere from 1 to 100
kilometers in size.
Meteoroids are chunks of rock floating in space. They are composed
primarily of iron and/or nickel. When they enter our atmosphere, they are
called meteors. Most meteors are so small that they burn up in the
atmosphere before reaching the surface. Twice a year Earth passes through a
meteor field. We can observe thousands of meteors burning up in the
atmosphere, called shooting stars. These are meteor showers. However, if a
meteor strikes the surface of Earth, it is called a meteorite. If a
meteorite is big enough, it will create an impact crater.
Where did all of this material come from? Astronomers suggest that about 5
billion years ago a small impact event like the Big Bang occurred, sending
remnants into space, coalescing into the planets, and other parts of the
solar system formed as a result. As the planets were forming, impacts from
rocks in space spun off material to form moons. As each celestial object
cooled, heavier and heavier elements formed, which led to layers inside the
objects. More on this later.
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Every planet has two motions � rotation (spinning in place around an
imaginary axis) and revolution (spinning around the sun). Rotation
determines the length of a day and is measured in hours while revolution
determines the length of a year and is measured in days. Both motions depend
upon a center of movement. Rotation has Earth�s axis while revolution has
the sun.
Every planet has an elliptical orbit, or an oval orbit. The orbit is never
a perfect circle. (At least not here.) How much of an oval depends on the
eccentricity of the orbit. Eccentricity is the flatness of the orbit. We
know that our orbit is elliptical and has eccentricity because we are closer
to the sun at some point in our orbit (winter) and further away at another
point (summer). We need two measurements for eccentricity � the distance
between the foci in the orbit and the length of the major axis of the orbit.
A focus is the point around which the orbit bends. The sun is one focus. The
other focus is imaginary. The distance between these two is important. The
smaller the distance, the rounder the orbit. The further the distance, the
flatter the orbit.
Every orbit has two axes. One is the minor axis, which measures the orbit
from top to bottom. The other is the major axis, which measures side to
side. We need the major axis. We divide the distance between the foci by the
major axis to get eccentricity.
Ecc = distance between foci
--------------------------
length of major axis
For Earth the distance between the foci is 5 million kilometers and the
major axis is 301 million kilometers (149 million kilometers from the sun at
our closest plus 152 million kilometers away from the sun at our furthest).
When we divide these two numbers, we get an eccentricity of .017
Notice that eccentricity is always a decimal!!!
If the distance between the foci is 75 million kilometers and the major
axis is 75 million kilometers, the eccentricity is 1 � a straight line. This
would mean that the planet would enter the sun.
If the distance between the foci is 0 because the sun is the center of the
orbit, and the major axis is any number, eccentricity is 0 � a perfect
circle, and no change in seasons.
The shape of an orbit depends on two forces � gravity and inertia. The sun
pulls everything into itself by its gravitational field, so all celestial
objects move toward the sun. At the same time, all celestial objects were
set in motion by the impact event that created the solar system so they try
to move in a straight line. The interaction between moving in a straight
line and moving towards the sun creates a circular path in space around the
sun. SEE NOTES FOR ILLUSTRATIONS!!! This interaction is greatest closest to
the sun and weakest further from the sun.
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Earth has two motions � rotation (spinning on its axis) and revolution
(moving around the sun). These two motions are responsible for illusions
witnessed in the sky on a daily basis. These illusions are called apparent
motions. Planets, the sun, the stars, and the moon all have apparent motion.
Apparent motion is the false appearance that a celestial object gives to us
because of Earth really moving. Real motion is Earth�s rotation and
revolution. These two motions are responsible for creating the apparent
motions that we witness. What are these apparent motions?
Since all planets are different distances from the sun, they all move
around the sun at different rates. Mars and the outer planets revolve around
the sun slower than Earth. This causes them to appear to move backwards in
the sky from time to time. This backward movement is called retrograde
motion. (SEE DIAGRAM IN NOTES). This retrograde motion is caused by Earth
catching up to these two planets as they revolve around the sun.
The sun gives us daylight. We all know when the day is beginning because we
see the sun rise. We know when the day ends because we see the sun set.
However, we already know that the sun does not revolve around anything.
Therefore, the sun�s rise and set are apparent motions of the sun. The
Earth�s rotation is responsible for these illusions of the sun. Another
apparent motion of the sun is the climb and fall of the sun in the sky at
different times of the year. These movements are illusions caused by Earth
reaching different points in its orbit around the sun.
Even stars have apparent motions. If we were to observe stars during the
night, we would see that they move across the sky during the night from east
to west. These movements are caused by Earth�s rotation during the night.
The moon�s apparent motion is appearing to rise 50 minutes later each day
and shifting slightly to the east every day. The real motion behind this
appearance is that Earth rotates 15 degrees per day, but the moon revolves
around us 11 degrees per day. This difference is responsible for the slight
shift and change in the rise of the moon.
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There are two ways of viewing the solar system, each one quite different.
The first way of viewing the solar system would be to use apparent motion as
the basis of our view. In ancient times people had only apparent motion to
use for their understanding. As was already implied in class, apparent
motion uses Earth as the reference point for all motion in the solar system.
Therefore, Earth is the center of this view. When Earth is the center, we
say that apparent motion is the basis for a geocentric model. This model has
Earth as the center of the solar system and everything revolves around
Earth. All the planets, the sun, the moon, the stars, and comets all had
orbits around Earth. The man who had developed this model was Ptolemy in the
first century AD. He was a Greek in Egypt at that time. This view of the
solar system was accepted until the 1500�s when telescopes were invented and
better instruments were available for observation. Motion was confusing
because nothing in space was observed to revolve around Earth, except the
moon. Therefore, a new model was needed.
Nicolaus Copernicus who was the first to notice a significant flaw in the
geocentric model of the solar system was an astronomer in the 1500�s. He
proposed that the sun was the center of the solar system. This new model,
which is accepted today as the correct view of the solar system, is called
the heliocentric model. This model is based on the real motions that were
discussed in class yesterday.
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Ptolemy is the man responsible for offering one of the first models of the
solar system with his geocentric model. He felt that Earth was the center of
the solar system, which he based on apparent motion. Fourteen hundred years
later, Galileo invented the telescope and observed celestial objects
revolving around the sun and not Earth. He was excommunicated by the
Catholic Church for his writings on this observation. This, however, led to
Copernicus developing the heliocentric model of the solar system, which he
published after his death for fear of excommunication.
Besides these three gentlemen, others were responsible for our current
understanding of the solar system. Tycho Brahe observed positions of the
stars and planets in the night sky over a twenty year period. From these
observations, he helped to disprove the geocentric model. His observations
were very important to another astronomer � Johannes Kepler.
Kepler studied Tycho�s writings and developed three laws of motion (NO, NOT
INERTIA). The first law of motion stated that all planets traveled in
elliptical orbits. At times the planets get closer to the sun, called
perihelion, and further from the sun, called aphelion. These were studied in
our discussion of eccentricity.
Kepler�s second law of motion stated that planets cover the same area in
space at all times as they travel in their orbits. (SEE DIAGRAM IN
NOTEBOOKS) This law is called the equal area law.
Kepler�s third law of motion, called the harmonic law, states that the
period of time it takes a planet to travel around the sun is related to its
distance. Specifically,
Period*Period = Distance*Distance*Distance
The last man responsible for our current understanding of the solar system
is Newton. He developed the universal law of gravity. This law states that
the gravity between two objects is strongest when they are closest to each
other. It also states that the bigger an object�s mass is, the stronger
gravity will be for it.
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Earth has two motions � rotation (spinning on its axis) and revolution
(orbiting the sun). Each motion has evidence on Earth that we use to support
its existence. Rotation has two evidences while revolution has one evidence.
Rotation is supported by the Coriolis Effect. This effect applies to air
and ocean currents on Earth as well as rocket launches and playing catch.
This Effect states that Earth rotates beneath us but objects on the surface
do not rotate at all. Air currents in the atmosphere do not touch the
surface and ocean currents in the water do not touch the surface. Therefore,
as Earth bends underneath these currents, they will travel in a straight
line. The result observed here is that these currents will bend as they
move. In the Northern Hemisphere, these will deflect to the right while in
the Southern Hemisphere, they will deflect to the left.
The second piece of evidence for rotation is the Foucault Pendulum, which
was named after the French physicist Jean Foucault. He hung a metal pendulum
about 60 feet above the ground in a room and set it in motion. All pendulums
swing at equal rates in the same direction always. However, what Foucault
observed is that the pendulum appeared to move in the room about 15 degrees
per hour. Since he knew how a pendulum worked, he concluded that the Earth
was actually moving.
Revolution is best explained by our observation of constellations. Certain
constellations (groups of stars in the sky that make a pattern) are visible
in summer while others are visible in winter. The reason we can�t see summer
constellations in winter and winter constellations in summer is because the
sun is between us and them. Hence, we move around the sun.
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There are two concepts of time for every location on Earth. The first
concept is local time, which is the time on our watches at any given point.
The second concept of time is solar time, which is based on the position of
the sun during the day. For example, local noon is 12:00 PM while solar noon
is when the sun is directly above us (usually at 3:00 PM.
Time is determined based upon rotation of Earth and longitude. Earth
rotates 360 degrees in 24 hours. There are 360 degrees of longitude;
therefore there are 15 degrees of longitude for every hour. Every 15 degrees
of longitude, therefore, is one time zone. We begin all time zones at the
Prime Meridian, which runs through, Greenwich, England.
Starting from Greenwich, England, we can identify the time zone to the west
by moving 15 degrees west, and we can identify the time zone to the east by
moving 15 degrees to the east. When we move east, we add one hour for every
time zone moved. For example, if we move 75 degrees east, we have moved 5
hours, so we will add 5 hours to our local time to determine the time at
that new location. If we move west, we subtract one hour for every time zone
crossed. For example, if we move 75 degrees west, we have moved 5 hours, so
we will subtract 5 hours to our local time to determine the time at that new
location.
The United States is so big that we cover several time zones. They are
(from east to west):
1) Eastern Time Zone
2) Central Time Zone
3) Mountain Time Zone
4) Pacific Time Zone
5) Alaskan Time Zone
6) Hawaiian-Aleutian Time Zone
Since Earth is round, it has no beginning or end. So, how do we determine
where each new day starts? We arbitrarily decide the location of each new
day. We use the International Date Line for this. If all meridians begin at
the Prime Meridian, then each new day begins right behind it at 180 degrees.
However, since nations extend beyond this point into other time zones (like
Siberia), the International Date Line is not straight. Rather, it wraps
around these countries in the Pacific so that the entire country has the
same time � and the same date because, moving to the east would cause a loss
of one day.
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There are eight phases, or appearances, of the moon. In order, they are:
1) New Moon
2) Waxing Crescent (First Crescent)
3) Waxing Quarter (First Quarter)
4) Waxing Gibbous (First Gibbous)
5) Full Moon
6) Waning Gibbous (Second Gibbous)
7) Waning Quarter (Second Quarter)
8) Waning Crescent (Second Crescent)
It takes the moon 27.3 days to make one revolution around Earth, but it
takes 29.5 days between one new moon and the next new moon. Why? The moon
has to sit just right between Earth and the Sun to be a new moon. The
realignment takes 2 days. If two full moons occur in the same month, we call
the second one a blue moon.
The moon�s orbit is elliptical around Earth. When it is closer to Earth, we
say that the moon is at perigee (�pretty close�). When the moon is further
from Earth, we say it is at apogee (�away�). The same is true for Earth�s
orbit around the Sun, except Earth is at perihelion (�pretty close� to the
Sun) or at aphelion (�away� from the Sun).
Because the moon�s rotation and revolution are the same, we never see the
other side of the moon. The only reason we know what it looks like is
because we have sent satellites there to photograph it.
When the moon is in New Moon, it rests between Earth and the Sun. It looks
like a giant black sphere in the sky. This is the phase the moon is in when
a solar eclipse occurs. The dark part of the moon�s shadow (the �umbra�) is
the area of a total solar eclipse while the lighter part of its shadow
(the �penumbra�) views a partial solar eclipse. Other areas of the world do
not see a solar eclipse because the moon is smaller than the Earth. Since
the Sun and the moon are in a direct line, both of their gravities work
together tugging on the oceans here. This tugging results in higher than
normal high tides (called spring tides) and lower than normal low tides
(called neap tides).
As the moon revolves, it begins to reflect the Sun�s rays. This makes the
moon appear white or yellow in the sky. We notice a banana shaped or
fingernail shaped sphere in the sky. This is the Waxing Crescent.
When the moon revolves around the Earth, it eventually sits at a 90 degree
to Earth. This is the Waxing Quarter. At this stage, the Earth experiences
high tides and low tides. Half the moon that we see is lit up; yet, that
half we see is only a quarter of the moon.
As the moon continues to revolve, it begins to light up more and more. More
than half the moon is finally lit up. This is the Waxing Gibbous.
When the moon sits behind Earth, it is fully lit up. We call it a Full
Moon. At this phase, there are again spring and neap tides for the same
reason as above. It is in this phase that a lunar eclipse may occur. When
Earth�s umbra covers the moon, it is a total lunar eclipse
while a partial lunar eclipse is when the moon sits in Earth�s penumbra.
Eclipses are not too common because the moon�s orbit around Earth is at a 5
degree angle to Earth, resulting in misalignment many times among the moon,
Earth, and the Sun.
As the moon leaves Full Moon, it begins to decrease in size (in terms of
what was lit). We enter the Waning Gibbous in this phase.
Eventually the moon and Earth sit at a 90 degree angle again. This is the
Waning Quarter. Once again, there are high tides and low tides.
When the moon is less than half lit up, it has entered the Waning Crescent.
Finally, the moon returns to New Moon.
Note: The shadowy side of the moon changes from left to right as the moon
revolves around Earth. Waxing stages are on the left while waning stages are
on the right.
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Energy/Insolation
Energy is the ability to do work. Most energy used by the Earth actually
comes from the Sun while only a fraction of energy used by Earth is actually
produced by Earth. As humans, we can see only a fraction of energy. All
forms of energy are part of the electromagnetic spectrum. This spectrum
consists of all energy forms � short-wave radiation, visible light, and long-
wave radiation. The fraction that we can see is the visible light � the
colors of the rainbow. These components of the electromagnetic spectrum are
electromagnetic energy � energy in the form of waves.
By referring to our reference tables, we can see that short-wave radiation
consists of gamma rays, x-rays, and ultraviolet rays. These all come from
the Sun and are absorbed by Earth�s atmosphere. These have high frequencies
because their wavelengths are small. Long-wave radiation consists of
infrared waves, microwaves, and radio waves. These all come from the Sun as
well as Earth. These bounce off Earth�s atmosphere because they have low
frequencies. Their wavelengths are large because of this.
The top of the energy wave is the crest. The bottom is the trough. The
height of the wave is its amplitude. The distance from crest to crest is the
wavelength. The number of wavelengths that pass by a given point in a second
is the frequency.
Once energy reaches an environment, it can interact with the environment in
one of 5 ways:
1) Refract, or bend. When we place an object in water (say, a straw),
it looks crooked. This is refraction.
2) Reflect, or bounce off. If the surface is smooth or light colored,
energy will reflect off the surface.
3) Scatter, or separate in various directions. If the ground is rough
or rocky, energy will bounce around between the cracks for a period of time
before leaving. This happens in deserts.
4) Transmit, or pass through an object. Light passing through a window
transmits. Light passing through a prism transmits.
5) Absorb, or enters the object. If the ground is dark colored, energy
will enter the object.
How smooth or rough the surface appears is called texture. If the surface
absorbs energy, it will give off energy. If a surface reflects energy, it
will be shiny.
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Once heat (energy) is introduced into an environment, it transfers itself
from one end of the environment to the other in one of three ways. These
ways are conduction, convection, and radiation. Where heat originated from
is called the source while the area where it settles is called the sink. The
source has a high concentration of heat while the sink has a low
concentration of heat.
Conduction is the transfer of heat energy from an area of higher
temperature to an area of lower temperature by direct contact. For example,
your mother always told you to never touch a pot while it was on the stove.
Yet, you did. What happened? You burned your hand! Why? Your cold hand
touched a very hot pot. The heat energy from the pot transferred to your
hand by direct contact. It transferred by conduction from the pot to your
hand. Why does this happen? There must be an equilibrium established between
the environment of the pot and the environment of your hand. Equilibrium is
a balance in temperature between the two objects. Since the equilibrium
constantly changes, we say that the equilibrium is dynamic, or ever-changing.
Convection is the transfer of energy between regions of higher temperatures
to regions of lower temperatures in a circular pattern. This transfer is
usually associated with liquids and gases. This transfer also results in
circular motions called convection cells. Warm air rises and cold air sinks.
Where is warm air found? Near the ceiling. Where is cold air found? Near the
floor. This is why you are cold in the winter if you sit or lay on the
floor. Yet, the warm and cold air are constantly in motion, rising and
falling in a convection cell.
Radiation is the transfer of energy by electromagnetic waves. Have you ever
noticed that the streets pulse when it is hazy outside, or that the window
is hazy when the radiator is running? This is because waves are produced in
these instances. What you are seeing is the movement of the waves.
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When energy enters an environment, it changes form as its speed slows. When
a high frequency form of energy enters an environment and slows, its
wavelength increases, causing it to change to another type of energy. For
example, when a gamma ray enters Earth from the Sun, it slows down and its
wavelength increases, becoming x-rays. The x-rays also slow down, becoming
ultraviolet rays, which in turn will convert to visible light.
There is always friction between energy and the environment it enters. The
friction creates heat, which affects the speed of the energy wave. When
things heat up, they move faster, so energy waves will increase at times
(think about the advisories on very hot days when the haze outside is
thick). Friction is also felt between wind and ocean waves, causing energy
transformations there as well.
Every object in the world has pent up energy (potential energy) which is
used when they move (kinetic energy). When a planet revolves, its potential
energy is greatest near the sun because the sun moves it along, while its
kinetic energy is greatest away from the sun because it needs to move on its
own to reach the sun again. Potential energy is greatest in massive objects
and objects highest above the surface. These two types of energy are
constantly being converted from one to the other.
We can measure the force of friction in an environment using temperature
(the measure of kinetic energy in an object). Temperature is the amount of
movement an object�s molecules have. Temperature is not energy but a measure
of the amount of energy present in an object. If molecules move quickly, the
temperature is high. If molecules move slowly, the temperature is low. We
can sense this temperature change when we feel hot or cold. We use a
thermometer to measure the kinetic energy in a substance. These days,
alcohol thermometers are used. There are three types of temperature scales
in existence. Two of them (Celsius and Fahrenheit) use the freezing and
boiling points of water as their basis. Fahrenheit is the scale used in the
United States. Fahrenheit is 1.2 degrees Celsius. Celsius is used throughout
the world. You do not need to know the conversion formula because these
scales are in your Earth Science Reference Tables. If we wanted to convert
46 degrees Fahrenheit to Celsius, it would be 8 degrees Celsius. If we
wanted to convert -15 degrees Celsius to Fahrenheit, it would be 4 degrees
Fahrenheit.
Kelvin temperatures are different. Kelvin uses absolute zero � the point
where no kinetic energy is detected in an object. It was discovered that
absolute zero equals � 273 degrees Celsius. Therefore, 0 degrees Celsius
equals 273 Kelvin and 32 degrees Fahrenheit. Practice using the three scales.
When two objects of different temperatures meet, there is energy transfer
between them. The amount of energy transfer is measured in calories. A
calorie is the amount of heat needed to raise the temperature of one gram of
liquid water one degree Celsius. The number of calories in each case is
referred to as the specific heat of an object. The rule of thumb here is
that solids require the least amount of energy to raise their temperature
because their molecules touch one another. Gases require the most amount of
energy to raise their temperature because their molecules are furthest
apart. Liquids are in between. However, liquid water requires the most heat
energy of all substances because of the unique way its molecules are
arranged. This is why land heats up faster than oceans. The specific heat of
major substances is in your Earth Science Reference Tables.
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Any changes in heat energy will cause the molecules to slow down or speed
up. Let�s look at both cases individually. If an object heats up, its
molecules spread apart. The spreading would cause molecules to move further
away from each other. In the case of a solid, this means that the solid
would melt into a liquid. In the case of a liquid, this means that the
liquid would evaporate into a gas. However, if the object cools off, its
molecules would contract into themselves. This contraction would cause the
molecules to move closer together. In the case of a gas, this means that the
gas will condense into a liquid. In the case of a liquid, this means that
the liquid will solidify into a solid.
For a substance to change phase, we need to add heat to it. We already know
that a substance needs a certain number of calories to change phase. We also
already know that at certain temperatures a particular phase is no longer
possible, and the substance will change phase. For example, we know that at -
17 degrees Celsius water is frozen as ice. If we add 34 calories of heat to
the ice, it will reach 0 degrees Celsius. At 0 degrees Celsius, though, ice
is no longer possible. It begins to melt. Yet, we still are adding heat to
it. Ice needs 80 calories to melt. If a thermometer were frozen in the ice
cube, it would register 0 degrees Celsius instead of more despite the 80
calories being added. The extra calories are used to change phase, not raise
temperature. Therefore, this heat energy being absorbed is referred to as
latent heat (hidden heat) because it is there internally for the molecules
to spread, but not to raise the temperature. Once 80 calories are absorbed
and the ice is melted, any extra heat added will register on the
thermometer. To heat water, we need 1 calorie for every degree raised.
Therefore, if we add 100 calories, the water will climb in temperature 100
degrees Celsius. At 100 degrees Celsius, liquid water begins to change phase
into gas. However, the temperature of the water stays at 100 degrees Celsius
despite the extra heat added because the extra heat is latent heat again.
Liquid water needs 540 calories to evaporate into water vapor. Once we add
the 540 calories, the temperature of the water vapor will climb. The same is
true if we reverse the order of the phase changes. The amount of latent heat
needed for phase changes is in your Earth Science Reference Tables.
A quick summary is needed here.
Specific heat � the amount of heat needed to climb 1 degree Celsius.
Latent heat � the amount of heat needed to change phase.
Specific heat � registers on a thermometer.
Latent heat � does not register on a thermometer.
Both types of heat require energy to be absorbed from somewhere. We already
know that Earth receives energy from the Sun and from its own core. The Sun
produces energy by nuclear fusion while Earth produces energy from the
pulsing of radioactive material in its core. The energy from both sources
are used to heat up substances, which will very likely result in phase
changes.
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1. The study of the earth�s motions is a starting point for
understanding the workings of the global ecosystem. The earth's two main
motions are rotation and revolution. Rotation is the earth turning on its
imaginary axis like a top. Revolution is the earth�s orbit around the sun.
2. The earth rotates west to east on its axis once a solar day.
Rotation produces a set of physical consequences such as the daily rhythm of
light and heat, the coriolis effect, tides, and the oblate ellipsoidal shape
of the earth.
3. Rotation is a device for establishing reference points and lines on
the globe such as the poles, equator, parallels of latitude and meridians of
longitude. Places on the earth's surface are located using a network of
lines called a geographic grid. Latitude is distance measured in degrees 0� -
90� north and south of the equator.
4. Longitude is the distance measured in degrees 0� - 180� east or west
of the prime meridian, an imaginary line from pole to pole passing through
Greenwich, England.
5. Earth�s rotation causes differences in time and date. Local time is
sun time as recorded on a sun dial. For convenience, we use standard time
which divides the world into 24 time zones. Fifteen degrees of longitude
equals one hour of clock time. Standard time in the United States is based
upon the time for standard meridians such as Pacific Standard Time 120� W,
Mountain Standard Time 105� W, Central Standard Time 90� W, and Eastern
Standard Time 75� W.
6. A new day begins at the International Date Line (180�). When
crossing this line westward, the calendar is moved forward to the nextday.
When crossing the line eastward, the calendar is moved back to the previous
day.
7. The earth revolves west to east in its orbit around the sun every
365 1/4 days (astronomical year). The plane of this orbit is called the
plane of the ecliptic.
8. The earth's seasons and different lengths of day and night are
caused by revolution, inclination (the 23 1/2� tilt of the earth's axis from
the perpendicular to the plane of the ecliptic) and parallelism of the
earth�s axial tilt.
9. The angle at which the sun strikes the earth�s surface varies with
latitude and season. At the equator, the sun is directly overhead at noon
(subsolar point) twice a year during the equinoxes; March 21 (Vernal
Equinox), and September 23 (Autumnal Equinox). During the equinoxes,the
circle of illumination (a line dividing the lighted portion of the globe
from the dark side) passes through the poles to give equal lengths of day
and night worldwide.
10. The northernmost and southernmost points to receive the sun�s direct
rays at noon are called the tropics. The sun is directly overhead at noon at
the Tropic of Cancer (23 1/2� North) on June 21, the summer solstice. The
sun is directly overhead at noon at the Tropic of Capricorn (23 1/2� South)
on December 22, the winter solstice.
11. As the earth changes its position relative to the sun, the length of
daylight also changes. The biggest differences in daylight occur during the
summer and winter solstices when locations within the Arctic and Antarctic
circles receive either 24 hour days or 24 hour nights.
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InSolAtion is incoming solar radiation. This refers to energy from the sun.
All energy that enters Earth is either absorbed or reflected by our
atmosphere. Most of the energy that enters Earth is visible light. This is
because visible light has a high frequency and short wavelength. The harmful
radiation (short wave radiation) generally slows upon entering our
atmosphere and changes into visible light.
Earth�s atmosphere absorbs ultraviolet light and infrared radiation. Both
of these types of energy is absorbed by the ozone layer in the upper
atmosphere. Water vapor, carbon dioxide, and methane absorb infrared waves.
The absorption increases the energy on Earth, raising the temperature.
However, the icy surfaces on Earth and the bodies of water reflect other
forms of energy that lower the temperature on Earth. This interaction
between absorption and reflection keeps temperatures balanced on Earth.
InSolAtion is affected by several factors. The first of these is the angle
of incidence. This is the angle at which the sunlight hits the Earth�s
surface. The closer the angle is to 90 degrees, the stronger the heat energy
is. This is why the Equator is hotter than the Poles. Sunlight strikes there
at 90 degrees while it strikes the Poles at almost 0 degrees.
The second factor is the texture of the surface. Smooth surfaces (ice and
water) reflect sunlight, lowering temperatures. Rough surfaces or rocky
surfaces absorb heat, raising temperatures. This is why deserts are hotter
than oceans and icy areas. When matter changes phase, heat is needed for
such phase changes. Therefore, the heat absorbed is not used to raise the
temperature, but to change phase. When ice caps are melting, the temperature
is still cool, although a lot of heat is absorbed while changing phase.
Whether you live near the coast or inland is important in understanding
temperature changes. Since water has a higher specific heat than land, its
temperature climbs slower than land. This is why coastlines are cooler in
summer than inland and warmer in winter than inland.
When we increase pollution, we increase the amount of carbon dioxide in the
air, leading to higher temperatures because heat can not pass through the
CO2 in the air to escape the atmosphere. This is what causes global warming.
However, a decrease in carbon dioxide levels or massive volcanic eruptions
are enough to block sunlight from entering Earth, causing Ice Ages.
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The amount of InSolAtion received by Earth is not constant. It always
changes. Think about when the highest or lowest temperatures are reached
during the day. This is proof of this. Earth�s shape, your latitude,
seasons, and the time of day are all factors determining how strong or weak
InSolAtion is.
Earth is round. The Equator bulges. Therefore, not all points will receive
sunlight at the same time or in the same amount. The closer you are to the
Equator, the stronger the energy is received because sunlight strikes at a
90 degree angle. The further you are from the Equator, the smaller the angle
is, resulting in less energy received.
Latitude is related to this directly. The lower the latitude, the hotter
the temperature, and vice versa. Enough said.
Seasons are a factor for the amount of InSolAtion because temperatures in
the summer are higher than in winter. This is because we face the Sun at a
more direct angle than in winter. This more direct angle results in more
energy absorbed by Earth.
The time of day affects InSolAtion because at different times, the Sun sits
at different angle sin the sky. When the Sun is at its highest point, we
receive the most energy. We receive the least energy when it is at its
lowest point.
We receive the most energy in summer and the least in winter. Just think
about the temperatures in those seasons. On the first day of spring/autumn
(spring equinox/vernal equinox) we receive exactly 12 hours of daylight and
night. Between spring and autumn, the days have more sunlight. This means
more energy and higher temperatures. Between autumn and spring the opposite
is true. Between the Arctic Circle and North Pole and between the Antarctic
Circle and South Pole, there are 24 hours daylight between spring and autumn
and 24 hours of night between autumn and spring because of the tilt of the
axis.
The hottest time of day is approximately 3:00 PM and the coldest is before
sunrise because it takes time to heat up and cool off. The hottest time of
year is July and the coldest time is January for the same reason.
What causes the seasons? Changes in the amount of moisture and temperature
causes seasons. How? When we revolve, we change position around the Sun.
These changes result in differences in the energy received here. Thus, a
seasonal change. The tilt of Earth�s axis also causes seasons because of an
imbalance in InSolAtion. Any changes here would cause extreme seasonal
shifts. When our orbit moves toward the Sun, temperatures rise, and if we
move away, temperatures fall.
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Earth has a heat budget that works the same way your parents� budget works.
The amount of heat received by the Sun should equal the amount of energy
emitted by Earth. If we receive more energy than we emit, we heat up. If we
receive less energy than we emit, we cool off. Energy is either reflected
into space or absorbed by Earth. The energy that is absorbed is circulated
through the atmosphere by conduction, convection, and radiation.
What happens when we receive too much energy? Global warming occurs, and
the polar ice caps melt. We go through natural periods of global warming,
when we move closer to the sun as our orbit shifts. However, our rate of
pollution these days is causing global warming too. Therefore, is this
global warming naturally occurring or artificial?
What happens when we receive less energy? We cool off, like in an Ice Age.
This occurs when our orbit shifts away from the sun, or massive volcanic
eruptions cause this. There have been at least seven Ice Ages in our history.
Sometimes wind patterns change when the heat budget shifts slightly. This
causes ocean currents to shift somewhat, resulting in hot summers and mild
winters. This is El Nino. It takes about seven years for El Nino to occur.
The heat budget shifts when the number of sunspots changes. When the sun
has more sunspots, it emits more energy and vice versa. The position in
orbit also affects the heat budget because of the change in seasons. If the
axis were to tilt more, temperatures would be cooler and if it were to tilt
less, temperatures would increase. Volcanic eruptions are another cause. See
above. Human actions (deforestation, desertification, pollution,
urbanization) all cause shifts in the heat budget as well.
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METEOROLOGY
Meteorology is all about weather variables, or those factors that change on
an hourly basis. These variables are: temperature, air pressure, wind,
moisture conditions, cloud cover, precipitation, and storms. All weather
(which is the study that meteorology focuses on) occurs in the bottom layer
of the atmosphere. That layer is called the troposphere. The troposphere
climbs up to about 8 miles above sea level (12 kilometers). All water vapor
exists in the troposphere only. As we climb through the troposphere,
pressure decreases as does temperature. That�s why it is so common for
planes to ice up during flight. All the heavier gases (oxygen, carbon
dioxide, carbon, nitrogen, hydrogen, etc.) exists here.
At an elevation of 8 miles (12 kilometers), there is a break in the
atmosphere called the tropopause. This is an interface between the
troposphere and the next layer � the stratosphere. Above this pause,
temperatures switch direction. This is called a temperature inversion. The
stratosphere climbs from 8 miles to 31 miles above sea level (12 � 50
kilometers). Pressure continues to drop, but temperature climbs as you
climb. No water vapor exists here. Therefore, no weather occurs here.
At 31 miles (50 kilometers), there is another interface called the
stratopause. Above this pause there is another temperature inversion. The
mesosphere exists from 31 to 50 miles above sea level (50 � 81 kilometers).
No water vapor exists here. Pressure continues to drop, and temperatures
drop as you climb.
At 50 miles (81 kilometers) there is yet another interface called the
mesopause, above which there is another temperature inversion. The
thermosphere exists here. There is no water vapor here. Pressure drops
rapidly, and temperatures soar here. This is the outer layer of the
atmosphere which receives a majority of the sun�s insolation.
We illustrate temperature on a weather map by connecting areas of equal
temperatures with isolines. The rules for drawing isolines are the same as
contour lines. See the notes on contour lines for more information.
How does the atmosphere heat up and cool off? Energy enters Earth. The
energy circulates through the atmosphere through convection. Warm air rises
and cool air sinks. The amount of greenhouse gases in the atmosphere also
determines the heating and cooling of the atmosphere. Conduction occurs when
warm air hits the surface and transfers directly into the immediate air
around the surface. Certain forms of electromagnetic energy is absorbed by
the atmosphere. Phase changes are also responsible for the changing of
temperatures in the atmosphere as is the Coriolis Effect moving the currents
around the Earth. The movement produces friction, which is measured as heat.
The changing temperatures of the air will affect density of the air, which
creates convection currents.
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Air pressure (also called barometric pressure or atmospheric pressure)
refers to the weight of air pushing down on a surface. It will continuously
change with changes in the environment. More dense air yields more weight,
resulting in more pressure. We measure air pressure using a barometer.
Mercury barometers are the most commonly used barometer. Standard air
pressure is 14.7 lbs/square inch, 29.92 inches of mercury, or 1013.2
millibars at sea level. This is called one atmosphere. We can convert from
inches of mercury to millibars using the Earth Science Reference Tables. To
use this table, just slide your finger across from inches to millibars and
vice versa (like we did with the temperature scales). We illustrate air
pressure on a map using isobars (lines that connect areas of equal air
pressure). The rules for drawing isobars are the same as for isolines and
contour lines.
What causes air pressure to change? Anything that will shift density will
change air pressure. Therefore, it is not surprising that when the
temperature shifts, air pressure will fluctuate. How? When air heats up, the
molecules expand, taking up more space. This increase in volume reduces
density. The lower density causes the air to rise. When temperature drops,
the molecules contract, taking up less space. This contraction increases
density, causing the air to drop.
When water evaporates into the air, its weight reduces the weight of the
air. Why? Water vapor weighs less than oxygen and nitrogen � the two most
abundant gases in the air. When more and more water vapor is present, the
air�s weight decreases. This decrease results in density dropping, making
the air rise. When the air loses water vapor, the air�s weight increases.
This increase leads to the weight of air increasing, causing the air�s
density to rise. Thus, the air sinks.
As we climb higher and higher up, the less air is present � especially
oxygen � which results in less weight above you. The reduced weight
translates into less density. Less density translates into less pressure.
The further down you descend, the more weight is above you, which translates
into higher density. Higher density translates into higher pressure.
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Wind is the horizontal movement of air parallel to Earth�s surface. We
measure wind using two types of instruments. The first is called a wind
vane. You have all seen these before. They sit on top of buildings or in
front of houses. They are shaped like arrows and spin when the wind is
blowing. The direction the front of the arrow points is the direction the
wind came from.
The second instrument is an anemometer. This is a series of semi-circular
cups that spin when the wind blows. The direction that the semi-circle faces
is the direction that the wind came from.
All wind blows from areas of colder temperatures to areas of higher
temperatures. This is why we feel cold when the wind blows. Put in another
way, wind blows from areas of higher pressure to areas of lower pressure.
The difference in pressure between two areas is called the air pressure
gradient, whose formula is found in the Earth Science Reference Tables. The
steeper the gradient, the stronger the wind. The gentler the gradient, the
weaker the wind.
Wind is measured in knots. A knot equals 1.15 miles per hour. The faster
the wind blows, the higher the speed will be. More on this later.
Two types of wind shifts are common. The first is a land breeze. The second
is a sea breeze. A land breeze is when wind blows from the land to the sea.
This occurs when high pressure sits over land and low pressure sits over
water. When does this happen? It happens when cooler air is over land and
warmer air is over water. For those of you who have been to the beach or
live near water, you know that this occurs at night.
If a land breeze occurs at night, then a sea breeze occurs during the day.
This is because water will heat up slower than land due to its higher
specific heat. This allows the land to climb in temperature faster than the
water, producing a lower pressure over land and a higher pressure over
water. This allows the wind to blow from the water to the land.
If we name these two wind shifts for where the wind came from and if wind
vanes/anemometers point to where the wind came from, it stands to reason
that winds are named for where they came from. The common wind types are
northeast winds, southwest winds, northwest winds, and southeast winds.
These winds are not named north, east, south, and west because the Coriolis
Effect bends them as they move. These winds are responsible for driving
ocean waves. When the wind comes in contact with water, friction is produced
that drives the waves. When we begin oceanography, we will study this in
depth.
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The atmosphere transfers energy by convection � warm air rising and cool air
sinking. Therefore, it should come as no surprise to anyone that the
atmosphere is composed of several convection cells. These cells are
sometimes called Hadley Cells because Hadley discovered them. There are
twelve cells in the world � six in the Western Hemisphere and six in the
Eastern Hemisphere. How are they situated?
Two cells are located between 60 degrees North and 90 degrees N � one on
each side of the world. There are two cells between 60 degrees N and 30
degrees N � one on each side of the world. There are two cells between 30
degrees N and 0 degrees latitude � one on each side of the world. There are
two cells between 0 degrees latitude and 30 degrees S � one on each side of
the world. There are two cells between 30 degrees S and 60 degrees S � one
on each side of the world. There are two cells between 60 degrees S and 90
degrees S � one on each side of the world. These are found in your Earth
Science Reference Tables. At 60 degrees N and S and 30 degrees N and S there
are jet streams, which are bands of air traveling at 200 miles an hour or
more. These streams drive all weather in the United States west to east.
This is why storms typically move from the Midwest to New York.
If you study the Earth Science Reference Tables, you will note that there
are several areas listed as Dry and Wet. When we studied pressure, we said
that more moisture equals low pressure. When we studied winds, we said that
wind drives moisture. Therefore, if you look at the wind direction, you will
see that at 0 degrees latitude and 60 degrees N and S there are wet areas
identified because winds converge (meet) there. These areas are areas of low
pressure. These are Earth�s low pressure belts.
At 30 degrees N and S as well as 90 degrees N and S winds diverge
(separate), driving moisture away, creating dry areas. These are Earth�s
deserts. These are also areas of high pressure. These are the high pressure
belts.
The Equator is referred to as the Inter-Tropical Convergence Zone, or ITCZ.
These are the tropics of the world. Winds converge in this zone. Hence, the
name of the zone. At 30 degrees N and S are the horse latitudes. At 60
degrees N and S are the trade winds. 0 degrees latitude is also the
doldrums.
Note that winds from 60 degrees to 90 degrees N are northeast winds, from
30 degrees to 60 degrees N are southwest winds, from 0 degrees to 30 degrees
N are northeast winds, fro 0 degrees to 30 degrees S are southeast winds,
from 30 degrees to 60 degrees S are northwest winds, and from 60 degrees to
90 degrees S are southeast winds. Any east wind is a prevailing easterly and
any west wind is called a westerly. These winds bend because of the Coriolis
Effect. These winds also drive the ocean currents. See the Earth Science
Reference Tables for the comparison.
Jet streams shift with the seasons. They follow the sun�s light. That�s why
in the summer they shift north because the North Pole is in total daylight.
This allows southwest winds to drive in dry air, heating up our city. In the
winter it shifts south toward the Equator because the North Pole is in total
darkness. This allows northeast winds to strike with cold air and plenty of
moisture. This leads to blizzards.
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So far, we have studied three weather variables � temperature, air pressure,
and wind. Now we are able to discuss the fourth weather variable � moisture.
We already know that, in order for moisture to enter the atmosphere, there
must be evaporation. Evaporation is the process by which liquid water
changes to water vapor as it heats up. Therefore, evaporation occurs when
temperature climbs. This is because the liquid water molecules gain enough
energy to leave the Earth�s surface. These molecules are much hotter than
the surrounding environment. Therefore, when the water molecules leave the
Earth�s surface, the rest of the environment remains cooler than the heated
water. As a result, the process of evaporation is a cooling process. Just
think of when you step out of the shower � you feel a chill as the water
evaporates from your skin.
Water vapor enters the atmosphere in several ways. The first way is through
evaporation. The second way is through plants� leaves. As you know, plants
are living organisms. They sweat. The process of plants sweating is called
transpiration. Collectively, the total amount of evaporation and
transpiration in the world is called evapotranspiration. The environment is
in equilibrium when the amount of evaporation and condensation are equal.
The rate of evaporation depends upon several factors. The first is the
amount of energy in the area. The higher the temperature is the more
evaporation will occur. Thus, the summer has more evaporation than the
winter. The second factor is the surface area of the water. The bigger the
body of water is the more interaction with air exists. This translates into
more evaporation. Thus, coastal areas have more evaporation than areas with
small streams. The third factor is the degree of saturation in the air. If
the air has a great deal of water already, evaporation will be less than if
the air is dry. Thus, the Equator has less evaporation than mid-latitudes.
The fourth factor is wind speed. Wind drives air, so if there is moist air
being driven out of an area by wind, there will be dryer air replacing it.
The rate of evaporation increases. However, if dry air is being pushed out
of an area and is replaced by moist air, evaporation is less.
The amount of moisture in the air is called humidity. Since different
temperatures can hold different amounts of moisture, the amount of moisture
in the air at a given temperature is called relative humidity. Humidity is
measured in grams of water vapor per cubic meter of air. I do not know about
you, but I have never heard a meteorologist give this unit of measure when
reporting humidity. Therefore, a meteorologist reports relative humidity,
which is the percentage of moisture in the air that can be held at that
temperature.
Meteorologists can calculate relative humidity by using a sling
psychrometer. A sling psychrometer is actually two thermometers in one. The
first thermometer measures the air temperature. This is the dry bulb
thermometer. The second thermometer has a wet wick attached to the bulb
which allows the water to evaporate. This is the wet bulb thermometer. The
wet bulb will always be equal to or less than the dry bulb temperature. The
difference between these two numbers is important. The closer they are to
each other, the more relative humidity there is. At 100% relative humidity
precipitation may occur because the air is fully saturated. See the Earth
Science Reference Tables to calculate relative humidity.
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The opposite of evaporation is condensation. Condensation is the process of
water vapor cooling into liquid water. For condensation to occur, there must
be particles floating in the air for liquid to attach itself upon. These
particles are called condensation nuclei. These include, but are not limited
to, ash, chemicals, pollen, and other small substances. When the liquid
water molecules become too heavy, they fall as precipitation. We will study
this later.
The point at which condensation forms is called the dew point. The dew
point is calculated the same way as relative humidity. Therefore, by using a
sling psychrometer, we can calculate the relative humidity and the dew
point. When the dry and wet bulbs are equal, the dew point is also that
temperature. It is that temperature that you will see moisture called dew on
the grass or your windows. When the temperature is below freezing, there
will be frost instead.
Sometimes there may be fog formed from condensation. Fog is a cloud on the
cloud. Clouds need condensation nuclei to form; therefore, fog forms when
condensation nuclei are near the ground. Furthermore, temperature inversions
are needed for fog to form. When the ground radiates heat on a clear night,
the heat is lost and the air cools off rather quickly, forming radiation
fog. When warm air blows from the south and there is snow on the ground,
advection fog forms.
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We saw yesterday that fog is a cloud on the ground and depends upon
condensation. Therefore, clouds in the sky also depend upon the same. Today
we will focus upon those clouds. Cloud cover is the fifth weather variable
that we will study.
There are three types of clouds � 1) cirrus clouds are feathery and exist
extremely high in the troposphere. Ice crystals are the basis of their
formation, 2) stratus clouds are formed in the lower troposphere. They are
layered clouds and are usually seen on a clear day, and 3) cumulus clouds
are formed by vertical development. A cumulonimbus cloud brings rain and
storms.
There are four families of clouds � 1) high clouds in the upper
troposphere, 2) middle clouds in the middle portion of the troposphere, 3)
low clouds near the base of the troposphere, and 4) vertical clouds which
bring moisture and storms. When a cloud is above freezing it contains
liquid, and when it is below freezing it contains snow and ice. Near 0
degrees Celsius contains both forms of water.
If temperature drops below dew point, water condenses. Above the surface a
great deal of condensation will produce clouds. The density of the cloud
allows us to see it. Low density clouds produce haze in the atmosphere or
fog on the ground. Cloud cover, therefore, is the amount of the sky covered
by clouds. A cloud�s base (the bottom of the cloud) is the point in the
atmosphere where the dew point and the air temperature are equal. For
different clouds, this is a different altitude. We need the Generalized
Graph for Determining Cloud Base Altitude in Appendix 3 on page 304 in the
review book. Dashed lines are dew point temperatures and solid diagonal
lines are air temperature. We have practiced this in class. To locate the
cloud base, do the following:
1) Find the temperature and dew point that you are given.
2) From the temperature mark, follow the diagonal upward and left.
3) From the dew point, follow the dash upward.
4) The place of intersection is the cloud base altitude.
The atmospheric transparency is the amount of insolation that is absorbed.
When more clouds exist, there is more reflection, resulting in less
transparency. When no clouds are present, more transparency exists because
more absorption is occurring. Transparency is directly related to visibility
(the amount of the surface you can see on a clear day expressed in miles).
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Precipitation is the falling of water from clouds in any form. Precipitation
forms when liquid water condenses onto condensation nuclei and its weight
increases to the point where the cloud no longer is able to support the
weight. That is the time that precipitation occurs. This point in time is
when the relative humidity is 100% and the dew point is the same as the
temperature.
There are six forms of precipitation that exists. The first is rain, which
is liquid water falling from clouds. When the cloud is above 0 degrees
Celsius, rain forms, regardless of the temperature on the ground. There are
two variations of rain here. Both variations are two other forms of
precipitation. Therefore, the second form of precipitation is drizzle. This
is when water droplets are very fine droplets of water. They are close
together and may fall slowly due to their size. It forms in clouds of
temperatures more than 0 degrees Celsius. The third form of precipitation is
freezing rain. The rain forms in clouds with temperatures more than 0
degrees Celsius, but it falls on grounds that are lower than 0 degrees
Celsius. The fourth type of precipitation is snow. This is solid water that
falls on the ground. You may see snow in areas where it is warmer than the
freezing point. This is because snow forms in clouds that have temperatures
lower than 0 degrees Celsius, regardless of ground temperatures. The fifth
form of precipitation is sleet. This forms in clouds above 0 degrees
Celsius, but the clouds are in areas that are below 0 degrees Celsius.
Therefore, it starts out as rain and freezes into ice pellets as it falls.
The sixth form of precipitation is hail. This forms in cumulonimbus clouds.
Hailstones start as ice crystals or frozen water droplets that collect more
moisture over time. The hailstone falls and is kicked up by a back draft of
wind, so that it returns to the cloud and collects more moisture, growing
heavier and falling again until it is heavy enough to pass the back draft
and reach the surface.
We measure precipitation with a rain gauge, which measures depth. Snow can
be measured with a ruler. 10 inches of snow equals 1 inch of rain. Rain
showers are fast and brief, like thunderstorms, while snow showers are fast
and brief periods of snowfall.
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Since different locations receive different amounts of insolation, their
temperatures will be different. This translates into different pressures and
different moisture conditions. We could recognize these differences on any
given day. A day that rains has different characteristics than a day that is
clear. This is because air moves in blocks. We call these blocks of air �air
masses�. The types of air masses that affect New York State are maritime air
masses, which form over the ocean and are wet, and continental air masses,
which form over North America and are dry. There are tropical air masses
that form along the Tropic of Cancer and are hot, and polar air masses that
form over Canada and are cold. Combinations of these are possible. The
combinations are:
1) maritime Tropical (mT) � wet and hot, forms over the central Atlantic
2) maritime Polar (mP) � wet and cold, forms over the North Atlantic
3) continental Tropical (cT) � dry and hot, forms over the American
southwest
4) continental Polar (cP) � dry and cold, forms over Canada
Since each of these air masses have different moisture and temperature
conditions, they have different pressure conditions. High pressure systems
are cP and cT while low pressure systems are mT and mP. Wind in high
pressure systems move in a clockwise direction from the center out because
the highest pressure is inside and the lowest pressure is outside. Wind in a
low pressure system moves in a counterclockwise direction from outside in
because the highest pressure is on the outside. High pressure systems have
clear weather because they are dry while low pressure systems have stormy
weather because they are wet.
The boundary between two air masses is called a front. A warm front is the
front of a warm air mass, a cold front is the front of a cold air mass, a
polar front is the front of bitterly cold air, a stationary front is the
front of an air mass that is hot and cold and won�t move, and an occluded
front is a combination of a polar front with another front.
When fronts meet each other, warm air rises over cold air, cools off,
condenses, and forms clouds that will ultimately bring rain. That is how
storms are born.
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Storms are violent disturbances in the atmosphere that create dangerous
conditions on the surface. Characteristics of storms include heavy
precipitation, strong winds, fronts, and low pressure. All storms that
affect New York State are called mid-latitude cyclones, or cyclonic storms.
Warm air is lifted over polar fronts and form low pressure that rotates due
to the Coriolis Effect.
One such storm is a hurricane. These storms form over tropical waters in
the Atlantic Ocean near Africa. They gain energy from the evaporation of
millions of gallons of water from insolation. The pressure gradients formed
as a result create winds of at least 74 miles an hour. Different parts of
the world call these storms hurricanes, typhoons, or cyclones, but they are
all the same. They all have clouds full of precipitation, an eye in the
center with the lowest pressure, and winds higher than 150 miles an hour.
Once a hurricane reaches land or cold water, it loses energy. Friction with
the ground kills a hurricane over land. Floods form on land and debris flies
due to the high winds.
A second type of storm is a thunderstorm. There are about 2000
thunderstorms at any point in time on Earth. These storms bring heavy
precipitation, thunder, and lightning. Severe enough thunderstorm clouds
could bring hail. Thunderstorm clouds are called cumulonimbus clouds. These
clouds form when warm air is forced to rise above cold air quickly. This
could occur along a cold front, in a warm air mass that comes in contact
with cool ground, or in a hurricane. The warm air rises, condenses, and
forms the clouds. There is constant upward movement forming the cloud while
precipitation falls at the same time. These two movements produce opposite
charges, expelling lightning, and producing thunder. Characteristics of
these storms include hail, high winds, lightning, and heavy rain. To avoid
being struck by lightning, lie down in an open area, stay in a car, don�t
touch electrical appliances, stay off the phone, etc.
A third type of storm is a tornado. Tornadoes are the most violent storm.
They are rapidly rotating, extremely low pressure funnel winds that hang
down from cumulonimbus clouds towards Earth�s surface. They must reach the
surface to be a tornado. They are narrow, but they can cover quite a
distance. They could reach speeds of at least 318 miles an hour, though it
is believed they can reach 350 miles an hour. We do not understand their
formation, but they form in late afternoon when it is warmest, and when
fronts that have a wide difference in temperature meet. The extremely low
pressure in a tornado �vacuums� up materials. Hide in a basement to avoid
danger.
The last storm is a blizzard. These storms have wind speeds of at least 35
miles an hour and heavy falling/blowing snow. They form at fronts during
winter. These disrupt life in general in many ways. Stay indoors where it is
warm.
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It is important to be able to predict the weather so that people know what
to prepare for the day to avoid danger when they step outside. All forecasts
are based upon the probability of an occurrence taking place. Meteorologists
use statistics from the past to create the forecasts they generate for us.
These statistics are collected over a wide time frame (ex: 30 years). Based
on these statistics, they could read the signs and produce their forecast.
Statistics are collected using satellites in space, radar detection of
electromagnetic energy waves off clouds, and Doppler technology that detects
echoes and changing weather conditions. Some simple relationships used by
meteorologists to forecast the weather are:
1) Air pressure is associated with changes in temperature.
2) Precipitation will occur as air temperature and dew point get closer
together.
3) If the air pressure gradient increases, so does wind speed.
All the statistics collected are put onto a weather map, where a circle is
plotted to represent the city where the statistics were collected. The
circle is the station and all symbols used there are the model. Therefore,
weather maps use station models. The complete list of symbols is in the
Earth Science Reference Tables. To create the model, plot the temperature
(without units) in the upper left, dew point (without units) in the lower
left, the visibility and the type of precipitation in the middle left in
that order from left to right. Air pressure is plotted in the upper right
using the last three numbers and no decimals, the amount of precipitation is
in the lower right, and the barometric trend is in the middle right. There
is no decimal here so the number is read as a decimal (it is understood that
way). For example, a pressure of 33 is read as �3.3�. A �+� in front of the
pressure is an increase in pressure, a �-� in front of the pressure is a
decrease in pressure. A �/� after the pressure means that pressure is
rising, a backwards �/� after the pressure means that pressure is falling,
and �-� after the pressure means that pressure is steady. Wind direction is
a line on the side of the compass that represents the wind direction. A
south wind is on the south side of the station while a northwest wind is on
the northwest side. Wind speed is represented by feathers on the line for
wind speed. A full feather is 10 knots while a half feather is 5 knots. A
wind speed of 15 knots is a full feather and a half feather.
If you need to read the model, keep these in mind. They will help. For
example, if a model has a pressure of 132, the air pressure is 1013.2
millibars. If it has a pressure of 999, air pressure is 999.9 millibars. All
pressure readings that are 500 or less start with �10� while all pressure
readings more than 500 start with �9�.
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