The Air Around You
Earth's atmosphere is the envelope of gases
that surrounds the planet.
up of nitrogen, oxygen, carbon
dioxide, water vapor, and many other
gases, as well as particles of liquids and
Weather is the condition of Earth's
Importance of Atmosphere
Contains gasses that living things need
Keeps surface of earth warm
Protects from dangerous ultra violet
Allows water to exist as a liquid
Prevents the surface from being hit by
most objects from outer space
Air pressure is the
result of the weight of a
column of air pushing
down on an area.
1013.25 hPa (hecto
29.92 inches of Hg
1 in x 1 in
14.7 lbs at
Measuring Air Pressure
Barometer is an instrument that is used to
measure air pressure.
Mercury barometer consists of a glass
tube open at the bottom end and partially
filled with mercury
At sea level, the
is 76cm high
Aneroid barometer has an airtight metal
chamber, no liquid
Air Pressure & Altitude
Elevation – the distance above sea level.
As altitude increases Air pressure decreases
As air pressure decreases, so does density.
Layers of the Atmosphere
four main layers
Troposphere – tropo = changing
sea level to 12 km (9 km at poles
and 16km at equator)
All weather occurs here
Has almost all mass of atmosphere
Temp. decreases with altitude
12 to 50 km
layer, protects from UV, jets
Temp. increases with altitude
(middle part of stratosphere has
ozone layer which absorbs energy
from the sun and converts it to heat)
from 50 to 80 km
earth from meteoroids;
burn with friction
Temperature decreases with
altitude (fewer ozone molecules)
Thermo = heat
• .001 percent as dense as the air at sea level
80 km to space
• Temp up to 1800°C even though air is very
thin, because sunlight strikes the
thermosphere first, N2 and O2 molecules
convert this energy into heat
Thermometer will show 0°C because there are
not enough molecules to touch collide with a
thermometer and warm it.
made up of 2 layers
Ionosphere – 80 km to 400
• Gas particles electrically
• Radio waves reflect back to
Earth from here
• Aurora borealis occur here
Exosphere – above 400 km
• Satellites orbit here
Layers of the Atmosphere
Energy in Earth's Atmosphere
Energy travels to Earth as electromagnetic
radiation from the Sun. EM Waves are
classified according to wavelength
(distance between waves)
1. Visible Light – VIBGYOR
Red and Orange – longest wavelengths
Blue and Violet – shortest wavelength
2. Infra Red – invisible, longer than red, felt as
3. Ultraviolet – invisible, shorter than violet,
cause sunburns, skin cancer, eye damage
EMR travels through the atmosphere &
heats the surface of the Earth
solar radiation is absorbed –
Ozone (UV Rays), water vapor, clouds,
dust, CO2 absorb energy
Reflected – clouds, dust particles,
Air molecules, like oxygen and nitrogen for
example, are small in size and thus more effective
at scattering shorter wavelengths of light (blue and
violet). This produces our blue skies on a clear
During sunrise and sunset the distance that the
light has to travel from the Sun to an observer is
at its greatest. This means that a large amount of
blue and violet light has been scattered so the light
that is received by an observer is mostly of a
longer wavelength and therefore appears to be
droplets are large enough to scatter
all visible wavelengths more or less equally.
This means that almost all of the light
which enters clouds will be scattered.
Because all wavelengths are scattered,
clouds appear to be white.
clouds become very deep, less and
less of the incoming solar radiation makes
it through to the bottom of the cloud,
which gives these clouds a darker
When Earth's surface is heated, it radiates
most of the energy back into the
atmosphere as infrared radiation.
This IR radiation is absorbed by water
vapor, CO2 , methane, and other gases
Amount of energy absorbed by atmosphere
and earth’s surface = amount of energy
radiated into space
Heat Transfer in the Atmosphere
Thermal energy - total energy of motion in the
particles of a substance
Temperature – the average thermal energy of
the substance particles
Heat - transfer of thermal energy from a hotter
object to a cooler one
Transferred in 1 of 3 ways:
Heating the Troposphere
is the horizontal movement of
air from an area of high pressure to
an area of lower pressure.
Winds are caused by differences in air
pressure caused by unequal heating of the
Wind Direction / Wind Speed
Wind speed is measured with an anemometer.
The name of a wind tells you the direction the
wind is coming from.
Local Winds - winds that blow over short
Sea breezes & Sand breezes are Local
Winds caused by the unequal heating of
Earth's surface within a small area.
It takes more energy to warm up a body
of water than it does to warm up an
equal area of land.
Sea Breeze – Local wind from an
ocean/lake to land
• During the day, the land warms up faster
than the water.
• The air over land is warmer than air over
• This warm air expands and rises, creating
low pressure area.
• Cool air blows inland from over the water
and moves under the warm air
Land Breeze – Flow of air from land to a
body of water.
• At night.
• Land cools more quickly than water.
• Air over land becomes cooler than air
• Warmer air over water expands and
• Cooler air from over land moves beneath
this warm air.
Global Winds occur over a large area.
Caused by unequal heating of the
• More concentrated energy falls at the
• Air over the equator is warmer and
less dense than air near the poles.
• This cause differences in pressure.
• At the earth’s surface, global winds
blow from poles to equator.
Because Earth is rotating, global winds do
not follow a straight path. The way Earth's
rotation makes winds curve is called the
Coriolis effect. In the Northern
Hemisphere, global winds curve to the
right. In the Southern Hemisphere, global
winds curve to the left.
Doldrums along the equator
The sun heats the surface. Warm air rises, cool
air moves in but is rapidly heated. Very little
pressure difference so very weak winds
Horse Latitudes around 30° N & S – no
1. Trade winds
blow from the NE between Equator & 30° N
and from SE between Equator and 30° S
High pressure at 30N and S (horse latitudes);
low pressure at equator
Prevailing Westerlies –
between 30° and 60° N and S
Blow towards poles
Important for weather of US
Polar Easterlies –
Cold air near the poles sinks and flows back
towards lower latitudes
Polar Front – region where polar eaterlies meet
the prevailing westerlies (60°N & 60°S) –
effects weather of US
High speed wind
currents about 200
to 400km per hour
10-15 km above
west to east
Travel around the
Time (min.) Temp. Sand Temp. Water Time (min.) Temp. Sand Temp. Water