Download The Atmosphere - Belle Vernon Area School District

The
Atmosphere
Section 11-1
Atmospheric Basics
Objectives:
• Describe the composition of the atmosphere
• Compare and contrast the various layers of
the atmosphere
• Identify three methods of transferring energy
throughout the atmosphere
Atmospheric Composition
The ancient Greeks believed that air along with
fire and Earth were fundamental elements that
could not be broken down into anything else
Atmospheric Composition
• Today we understand that “air” is a
combination of gases, each with its own
unique set of characteristics.
• Together these gases form the Earth’s
atmosphere
Atmospheric Composition
•
•
•
•
•
•
78% nitrogen
21% oxygen
0.03% carbon dioxide
0.04% water vapor
0.02% argon
0.01% hydrogen
Atmospheric Composition
The percentages of nitrogen and oxygen are
critical to life on Earth and stable, the lesser
gases are subject to small changes that can
have dramatic effects
Key Atmospheric Gases
The percentage of water vapor in the
atmosphere varies with the seasons, the
altitude of the air mass that it is in, and the
surface features beneath the air
Key Atmospheric Gases
• The amount of carbon dioxide also varies
with season and human activity.
• Water and carbon dioxide are critical in
regulating the amount of heat the
atmosphere absorbs and retains.
• They regulate the Earth’s climate
Dust, Salt, and Ice
These three substances in
the atmosphere play a huge
role in cloud formation
Ozone
Ozone is a gas made up of three oxygen
molecules that exists high up in the
atmosphere
Ozone
Ozone is an important component of the
atmosphere because absorbs the harmful ultraviolet radiation released by the sun
Structure of the Atmosphere
The atmosphere is made up of five different
layers that each vary in temperature and
composition
The Lower Atmospheric Layers
The closest layer to the Earth’s surface is called
the troposphere, it makes up the bulk of the
atmosphere.
It is where the weather occurs,
extending an average of 12 km
above the surface
The Lower Atmospheric Layers
The stratosphere is the second layer up and
contains most of the ozone.
The Upper Layers of the
Atmosphere
• The mesosphere is the third layer up and
contains very little ozone or oxygen.
• The thermosphere is the fourth layer up and
is actually 1000 degrees C but the gas
molecules are so spread apart that they
cannot hold the heat.
• The exosphere is the fifth layer up and is the
boundary between Earth and outer space
The Sun is the source of all of the energy
in the atmosphere, this energy is
transferred to the Earth and throughout
the atmosphere in three ways.
Radiation
• Radiation is the transfer of energy through
space by visible light and ultra-violet
radiation
• Due to the reflection of the Suns light by the
oceans and the atmosphere only 50% of the
Suns light is actually absorbed by the Earth’s
surface.
Radiation
• The surface of the Earth absorbs light and
heat at different rates due to differences in
the amount of vegetation and water
• The atmosphere is not heated up directly by
sunlight, but by the heat rising as the land
heats up from the sunlight
Conduction
Conduction is the transfer of energy (heat) that
occurs as molecules collide and spread their
energy around. Heat of contact.
Convection
• Convection is the flow of energy by the flow
of a heated substance.
• As substances are heated, they rise.
• As substances cool, they sink
• This cycle makes energy move and even
causes wind and the weather
Section 11-2
State of the Atmosphere
Objectives:
• Describe the various properties of the
atmosphere and how they interact
• Explain why atmospheric properties change
with changes in altitude
Temperature vs. Heat
• Most people think that they are the same
thing…they are not.
• Temperature is a measure of how quickly or
slowly molecules move around
• Heat is the transfer of energy that occurs
because of the difference in temperature
between substances
Measuring Temperature
• Temperature can be measured in three ways
– Fahrenheit
– Celsius
– Kelvin (-273C and -523F)
Dew Point
• Dew point is the temperature to which air must be
cooled at constant pressure to reach saturation
• Saturation is the point at which air can no longer
hold water vapor anymore
• Condensation occurs when vapor changes into
liquid
Vertical Temperature Changes
• The height at which condensation occurs in
the atmosphere is where the base of the
cloud layer is because clouds are made from
water droplets.
Air Pressure and Density
• Just like the water in the ocean, air has mass
and constantly exerts pressure on our bodies,
our bodies have adapted to this pressure and
we barely notice these changes.
• The pull of gravity forces “air” gas particles
more toward the Earth’s surface
Pressure-Temperature-Density
In general, as temperature goes up
density goes down and as temperature
goes down density goes up.
Pressure-Temperature-Density
If the density of an air mass remains constant
(the number of particles remains the same),
then if the temperature goes up the pressure
goes up. If the temperature goes down, the
pressure goes down.
Wind
• Cool air is “heavy” or dense and wants to
sink, as it does it pushes the warmer “less
heavy” air upwards to fill in the space. This
exchange causes wind
• It occurs all the time, if the change in temp is
sudden you get strong winds.
Relative Humidity
• The amount of water vapor in the air is called
humidity.
• Warm air can hold more water vapor than
cold air, as it get colder in the winter…it
won’t snow as much
• The amount of water vapor a mass of air
actually holds compared to what it can hold
altogether is called relative humidity
100% Humidity (Saturated)
Section 11-3
Moisture in the Atmosphere
Objectives:
• Explain how clouds are formed
• Identify the basic characteristics of different
cloud groups
• Describe the water cycle
Cloud Formation
• Clouds form when warm moist air rises,
expands, and cools in a convection current.
• As the air reaches its dew point, the water
vapor in the air condenses around a
“condensation nuclei” (dust) and a cloud
forms
Cloud Formation
• Clouds can also when wind encounters a
mountain and has no where to go but up and
the air cools and water vapor condenses
• A third way that clouds can form is when a
warm and cold air mass meet and the water
vapor in the warm air begins to cool and
condense
Stability
• Stability is the ability of an air mass to resist
rising.
• If a warm air mass flows over a cold land
surface, the heat will flow to the land and the
air mass will tend to not rise
• If cold air flows over a warm land surface, the
cold air will absorb heat and rise, making it
unstable
Latent Heat
• Heat is stored in water droplets when they go
from water vapor to water droplets. When it
begins to rain, the energy is released and this
contributes to thunderstorms.
Types of Clouds by Height
• Clouds are generally classified using a system
developed by the Englishman, Luke Howard,
in 1803
– Low Clouds (Strato below 2000 feet)
– Middle Clouds (Alto between 2000 and 6000
feet)
– High Clouds (Cirro above 6000 feet)
Types of Clouds by Shape
Nimbus
Stratus
Cumulus
Cirrus
Nimbus (Low, gray, rain clouds)
“cloud”
Stratus (featureless sheets of clouds)
“layer”
Cumulus (puffy, white)
“pile or heap”
Cirrus (wispy, stringy)
“hair”
When cloud droplets collide,
they form larger and larger
droplets, until they get heavy
enough to fall as precipitation
(rain, snow, sleet, and hail)
Coalescence