Transcript Chapter 23 : Characteristics of the Atmosphere

The Atmosphere
BIG Idea:
• The composition, structure, and
properties of Earth’s
atmosphere form the basis of
Earth’s weather and climate.
Who studies atmospheric
conditions?
•Meteorologists…that’s who!
• How would you describe the
difference between
WEATHER and CLIMATE?
I. Characteristics
of the Atmosphere
• Weather = day-to-day changes
in atmospheric conditions.
•These conditions include:
•Temperature
•Air movements
•Moisture content
• Climate = general weather
conditions averaged over
many (about 30) years
A. Composition of the
Atmosphere
•
•
•
•
78% Nitrogen
21% Oxygen
0.9% Argon
0.1% Other
• Ozone – protects us
from harmful UV
(ultraviolet) rays
Damaged by CFCs
(poisons in ACs
and refrigerators)
Ozzy Ozone
• Have you
noticed the
weather
today?
• How would
you describe
it?
B. Properties of the
Atmosphere
1) Temperature
2) Air Pressure
3) Humidity
1. Temperature
• measure of the
average kinetic
energy of particles in a material
• more energy = moving faster =
higher temperature
• measured with a thermometer
2. Atmospheric (Air)
Pressure
• the ratio of the force of the
air to the area of the surface
on which it presses
• the weight of the atmosphere
pressing down on Earth’s
surface
BAROMETER
• an instrument that measures
atmospheric pressure
a. Mercurial Barometer
b. Aneroid Barometer
• Aneroid = ‘without liquid’
3. Humidity
• the amount of water vapor in
the atmosphere at a given
location on Earth’s surface
C. Layers of the
Atmosphere
- Based on temperature
differences, scientists
identify four layers of
Earth’s atmosphere
- Each layer is separated by a
“pause”
• Visualizing the Layers of the
Atmosphere
1. Troposphere: all weather
occurs here
• Layer closest to Earth’s surface
2. Stratosphere: where most
of the ozone is
3. Mesosphere: coldest layer
(-90°C )
4. Thermosphere: hottest
layer (over 2000°C); nitrogen
and oxygen atoms absorb
solar energy
• Components of the Atmosphere
- Quiz
II. Solar Energy
A. Radiation: all
forms of energy
that travel
through space
as waves
What happens to solar energy
that reaches Earth’s surface?
1. reflected (sent in a new
direction), or
2. absorbed
• Why does the
inside of a
closed parked
car heat up,
while the
windows stay
cool?
B. Greenhouse Effect:
atmosphere traps (long) infrared
rays
• The Sun’s energy
is trapped
inside.
• What are the ‘greenhouse
gases’ that trap heat within
our atmosphere?
1. Water vapor
2. Carbon dioxide
 produced by humans
 burning of fossil fuels (oil,
gas, coal)
C. Heat Energy Transfer
1. Convection: transfer of heat
energy in gases or liquids due
to density differences.
2. Conduction: transfer of heat
energy through matter from
particle to particle;
most effective in
solids.
3. Radiation: waves that directly
transport energy through
space; brings
HEAT to our
planet.
III. Winds
• Created by uneven heat
distribution at Earth’s surface
–The amount of energy
reaching any given point on
Earth’s surface is controlled
by the angle of sunlight
striking the surface
• What causes the amount
of energy to vary?
• Our tilt!
• Where on Earth will you
receive more of the sun’s
energy per unit area?
• Where will you receive
less?
• The Coriolis Effect: Earth’s rotation
causes winds to deflect (curve) to
the right in the Northern
Hemisphere and to the left in the
Southern
Hemisphere.
• Same with water
A. Global Winds
Winds are named according to the
direction FROM which they flow!
1. Trade Winds (Tropical Easterlies) –
winds in both hemispheres
flowing towards the equator
 between 30° (N and S) and 0°
latitude
a. Doldrums – weak and
unpredictable air mix, 5° N and S
of the equator
*winds CONVERGE here to form an
area of LOW pressure
b. Horse Latitudes – very weak air
movement 30°- 35° N and S
2. Westerlies – between 30° and 60°
N and S.
3. Polar Easterlies – weak winds at
60° N and S that flow away from
the poles.
TICKET ITEM!!
• Why does warm air rise
from the equator, and cold
air sink at the poles?
4. Jet Stream – bands of highspeed high-altitude westerly
winds.
B. Local Winds / Breezes
1. Sea Breeze – in the daytime,
winds from cooler water replace
warm rising land air
2. Land Breeze – at night, winds
from cooler land replace warm air
over the water
3. Valley Breeze – in the day
warm air rises UP the valley
4. Mountain Breeze – at night, cool
air sinks DOWN the mountain
What causes weather?
• uneven heating by the
Sun due to Earth’s axis
tilt
• energy transfer between
Earth’s surface and the
atmosphere