*
*Describe what weather is, what
affects it, and where it occurs.
*Explain the connection between
air pressure and wind.
*
*atmosphere - The layer of gases
that surround Earth.
*troposphere - The layer of the
atmosphere closest to the surface
*insolation - The amount of the Sun’s
energy that reaches earth at a
given time or place.
*air pressure - The force exerted on a
given area by the weight of the air
above it.
*convection cell - A circular pattern of
rising air, sinking air, and winds.
*sea breeze - Wind that blows from sea
to land.
*land breeze - Wind that blows from
land to sea.
*Coriolis effect - The shift in winds to
the right or left caused by Earth’s
rotation.
*
*As you climb a high mountain, the air
gets colder.
*This change in temperature would
occur because you were traveling
upward through the atmosphere, the
layers of gases that surround Earth.
*The atmosphere extends about 700
kilometers high.
*The layer of the atmosphere closest to
Earth’s surface is the troposphere; this
is where most of our weather occurs.
*The troposphere is about 11 kilometers
(7 miles) thick and contains about 80
percent of the total amount of air in
the atmosphere.
*Air is mainly a mixture of gases, dusts,
and water vapor.
*Jet airplanes normally fly within the
stable stratosphere; the stratosphere
contains the ozone layer, which absorbs
the harmful rays from the Sun.
*Rock fragments from space sometimes
burn up in the next layer, the
mesosphere, where the coldest
temperatures are found.
*The outermost layer the thermosphere,
is where space shuttles orbit.
*
Weather is the state of Earth’s
troposphere at a given time and place.
Weather variables which include
temperature, wind, moisture, cloud
cover, and precipitation can change
periodically.
*People have always tried to predict
weather.
*The ancient Egyptians relied mainly
on stars so they would know when
the Nile River would flood.
Scientists can obtain data
by using weather balloons
which get readings while
going through the
atmosphere, weather
satellites which provide
information from space,
and Doppler radar can show
an area’s current weather,
including precipitation,
wind direction, and wind
speed.
*
Fact and Opinion
“Oxygen is the most important gas in
the troposphere, because people need
it to breath.”
Is this a fact or an opinion? Explain.
This statement is an opinion because we
need all of the gases equally.
They all support our and other living
organisms life functions.
Critical Thinking
Why is it important to be able to
predict the weather accurately?
How to dress appropriately,
whether food must be gathered in
advanced,
when to plant or harvest crops,
and to know when to build shelter.
*
*In February it might be hot in
Argentina and cold in Michigan
because as the sunlight reaches the
Earth, the Sun’s energy penetrates the
atmosphere at different angles and
warms Earth’s surface.
*As the surface is warmed it also
warms the air above it.
*The angle of insolation is the angle
at which sunlight hits Earth’s
surface.
*As the angle of insolation increases,
the air becomes warmer.
*The greater the angle, the more
intense the Sun’s rays.
*The rays are the most intense when
the Sun is directly overhead.
*The angle of insolation depends on
several factors: latitude, time of
year, and time of day.
*The angle is greater near the
equator and smaller near the poles.
*The Sun’s rays are less
concentrated and more spread out
near the poles, so they do not warm
the surface there as much.
*Because Earth is on a tilted axis,
seasonal differences affect
insolation.
*In the summers of the Northern
Hemisphere, the Sun’s rays hit Earth
at steeper angles than it does for
the winter.
*Insolation also varies during the course
of the day.
*At dawn, the Sun appears close to the
horizon, and the angle of insolation is
small.
*By midday, the Sun appears much
higher in the sky, and the angle of
insolation is the greatest.
*At dusk, the angle of insolation is
small once again.
*You can measure the angle of
insolation by the shadows it casts.
*The shorter the shadow, the steeper
the angle of insolation.
*
*We use three different scales, the
Fahrenheit scale, the metric Celsius
scale, and the Kelvin scale.
*The Kelvin scale does not have any
negative numbers.
*Water freezes at 320F, 00C, or 273 K.
Water boils at 2120F, 1000C, or 373 K.
*An average room temperature is about
720F, 220C, or 295 K.
*
Fact and Opinion
“Solar energy enters the atmosphere
and warms Earth’s surface and the air
above it.”
Is this a fact or an opinion?
This is a fact, based on evidence.
The Sun’s energy’s warming of Earth is
not an opinion.
Critical Thinking
Why does the angle of insolation
change between midday and
evening, and how does this affect
the air temperature?
The angle of insolation decreases
because of Earth’s rotation, and the air
temperature usually decreases.
*
*Leaves scatter in the wind because the
force of the impact of the air particles is
what pushes the leaves.
*Air particles still move even if it is not a
windy day.
*Air particles have mass so Earth’s gravity
attracts them.
*Standard air pressure or the air pressure
at sea level is about 1 kilogram per square
centimeter.
*A balloon that is filled has expanded
until the air pressure inside the balloon
is higher than the air pressure outside
the balloon.
*When you release the balloon the higher
pressure air can escape, reducing the
pressure inside the balloon.
*When air flows out of the balloon,
moving from an area of high air pressure
to an area with low air pressure it is
called wind.
Earth’s air pressure varies; the higher
you go - the less air pressure. This
happens because there aren’t as many
air particles being pulled toward Earth
by gravity.
Air
pressure
variations
help
produce
wind.
As air warms it spreads out and takes up a
larger area resulting in less air in a given
volume. The air is then less dense and its
pressure decreases. Warmer air with lower
density and pressure rises above cooler air.
*
If a nearby place is warmer and at a
lower pressure, air will move from
the high-pressure area to a low-
pressure area.
This is called surface wind.
Unequal heating and cooling of a
region’s air forms a convection cell.
*
During the day the wind blows from the
water to the land, a sea breeze; at
night the wind usually reverses, going
from the land to the sea, a land breeze.
During the day, air expands over the
land faster than air over water, and the
cold air blows towards land.
Anemometer is a device that has cups
on it, it measures wind speed.
A weather vane is a device that
measures the wind’s direction; the
arrow points in the direction the wind
blows.
*Barometer measures the surrounding air
pressure.
*The old
barometers
measured the air
pressure in
millibars, the air’s
ability to maintain
the height of a
column of
mercury.
*
Fact and Opinion
"Land breezes are more refreshing
than sea breezes." Is this statement a
fact or opinion? Explain your answer.
This statement is an opinion. It is based
on one’s preference, not on facts.
Critical Thinking
What role do changing air temperatures
play in a convection cell?
In a convection cell, warm air rises and is
replaced by surrounding cooler air. As the
warm air cools, it sinks, and completes the
cycle.
*
*Winds blow from
areas of higher
pressure to areas of
low pressure.
*However, Earth’s
rotation pushes the
winds to either the
right or the left; this
is called the Coriolis
effect.
*The Coriolis effect causes winds in the
Northern Hemisphere to curve to the
right, or clockwise.
*In the Southern
Hemisphere,
the winds curve
to the left, or
counter-
clockwise.
*
*Global winds are sometimes called
prevailing winds.
*The Coriolis effect causes these winds to
curve.
*Trade winds, the winds that blow toward
the equator, are curved to the west by
the Coriolis effect.
*The winds that blow towards the poles
curve to the east.
*They are called westerlies.
*These
winds are
referred to
by the
direction
from which
they come.
*
Fact and Opinion
“The Coriolis effect causes winds to
curve to the right or the left.” Is this
statement a fact or an opinion?
Explain your answer.
It is a fact, based on verifiable evidence.
Earth’s rotation pushes the winds to
either the right or the left, this shift is
called Coriolis effect.