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THE ATMOSPHERE
18.1
The Atmosphere Made up of mainly two
gases:–Nitrogen 78%–Oxygen 21%–Trace Gases 1%
Layers of the Atmosphere
made up of 5 layers:–Troposphere–Stratosphere–Mesosphere– Ionosphere–Thermosphere
1. Troposphere The atmospheric layer we live in. Almost all weather occurs here. Contains water vapor and oxygen. Highest density Temps decrease as you increase
altitude until you reach the top of the layer called the tropopause.
Troposphere Within the troposphere a
temperature inversion may occur. This is a condition where warmer
air traps cooler air near the Earth’s surface.
This can cause air to get thick with pollution, where it can’t escape.
Temperature Inversions
2. Stratosphere– Lacks O2 and water vapor. (no weather)
– Contains the ozone (O3) layer. (this layer absorbs solar UV radiation)
– Temperatures increase as you gain altitude.
– Higher altitude than most aircraft would fly
Stratosphere
3. Mesosphere–The coldest of layer of the atmosphere. (-800C)
–Temperature decreases with altitude
4. Ionosphere Consists of upper mesosphere and lower
thermosphere. Contains charged ions that reflect radio waves
allowing transmissions to travel great distances.
Radio waves will travel farther at night than during the day. (less ions)
Where the aurora borealis can be seen. (excited photons)
Aurora Borealis – Northern lights
5. Thermosphere Most outer layer. Hottest layer (9800C) temperatures will increase with increase altitude
It absorbs solar radiation
Early Atmosphere Early atmosphere was much
different during Earth’s early days.
Volcanic eruptions released H2, ammonia, methane. CO, CO2 and N2.
No oxygen was present
Changing Atmosphere
Around 2.5 billion years ago single celled organisms evolved to capture the suns energy and CO2 to start the photosynthesis process
Then plants began appearing releasing oxygen into the atmosphere.
Present Atmosphere 350 million years later aerobic
organisms came along and balanced the atmosphere.
They took in oxygen and released carbon dioxide as a by product during respiration.
And thus the O2 and CO2 cycle was created.
Carbon Dioxide/ Oxygen Cycle
Our effect on the atmosphere.#1 Natural Stratosphere Ozone
Protects us from UV radiation. Can be destroyed by
chlorofluorocarbons or CFC’s Used during 1950s thru 1980s
in refrigerators and spray cans. CFCs are now banned in most
countries Ozone layer is repairing itself
#2 Man-made Ozone Ozone while helpful in stratosphere, is very toxic if trapped in the troposphere.
Main gas pollutant from cars, trucks, factories that causes smog.
Ozone Issues:
Greenhouse effect The process by which the
atmosphere traps some of the energy from the sun in the troposphere.
CO2, water vapor, and other gases absorb the suns energy (greenhouse gases)
Keeps the planets climate balanced
#3 Enhanced Greenhouse Effect
We are adding more and more CO2 and other greenhouse gases into the atmosphere:– Forest fires and volcanoes– Air Pollution from fossil fuel burning
– Increasing human population– Decrease in plant life and rain forest
– Increase of cattle grazing
Melting Ice Caps
Melting Glaciers
Rising Sea levels
Increasing Extreme Weather Events
WATER AND WIND
18.2
The Water Cycle The continuous movement of water from atmosphere to Earth and back.
4 mechanisms of travel
The Water Cycle Water enters the
atmosphere:1.Evaporation
Evaporation occurs at the lakes, rivers, and oceans.
2.Transpiration evaporation of water through plant’s leaves.
Transpiration
The Water CycleWater Exits: 3. Condensation
Water vapor rises until it is cool enough to condense to form clouds.
4. Precipitation When the cloud become full of
water droplets they will release moisture back down to Earth in the form of rain, sleet, ice, or snow.
Condensation
Evaporation
Water Vapor Water vapor is always in the air Humidity
– The quantity/amount of water vapor in the atmosphere
Relative humidity (percentage)– is the actual amount of water in the atmosphere compared to maximum amount it can hold.
The higher the temperature, the more water that can be held in the air.
Dew Point The temperature at which
water vapor molecules start to form liquid water.
Higher the humidity the higher the dew point.
dew point
Clouds Made up of tiny condensed droplets of liquid water.
3 main types
1. Cirrus Clouds highest altitude clouds
appear wispy and light.
Cirrus Clouds
2. Stratus Clouds layered or sheet like clouds
form at lower altitudes.
Stratus Clouds
3. Cumulus Clouds white and fluffy appear at many levels.
Cumulus Clouds
Other Clouds Other clouds are a
combination of the 3 cloud types.
The root nimbus means the cloud contains precipitation. (grayer color)
Ex. cumulonimbus produce thunderstorms
Nimbostratus
Cumulonimbus
Air pressure (Barometric Pressure)
The pressure due to the weight of the atmosphere.
Measured with an instrument called a barometer.
Air pressure decreases with altitude in the troposphere
Mercury Barometer
Wind Caused by differences in air
pressure between air masses. The greater the difference
the stronger the wind. Air always flows from high
pressure to low pressure– Pressure inside a plane is greater, so air would be sucked out if a window broke
Cabin Pressure
Wind and the Earth Coriolis effect.the change in direction of an object’s path due to Earth’s rotation.
Wind and the Earth Winds in the Northern hemisphere curve right.
Winds in the southern hemisphere curve left.
Weather The condition of the
atmosphere at any given time
Weather is caused by traveling air masses.–Large bodies of air with the same general characteristics throughout.
Fronts A boundary where two air masses with different densities meet.
Fronts cause precipitation, change in temperature, and a change in wind direction.
Front Types Warm front-warm air moves over cooler air forming clouds.
-Produces steady rain or snow for a couple of days.
Cirrus and cirrostratus clouds
Front Types Cold fronts-Cold air moves under slow moving warm air
-Brings high winds, thunderstorms, and possible tornadoes.
Cumulonimbus clouds
WARM/COLD FRONTS
Stationary Front
Two air masses meet Neither is displaced Air masses move side by
side Similar to warm front
weather
Weather Events 1. Thunder Storms
Lightening is caused by a build up of electrical charges from water droplets and ice crystals in clouds.
When opposite charges are found on the ground or other clouds, lightening strikes.
Thunder is the sound of lightening.
Thunder Storm Safety
If you count to 10 or less after seeing lightning before hearing thunder, then the storm is less than two miles away.
2. Tornadoes Form during severe
thunderstorms. Form from cool air from the
north, and warm air from south.
Tornadoes begin as a funnel cloud that intensifies until it touches ground
Most violent winds on Earth 310mi/hr
Most common in the Midwest
3. Hurricanes Very large storms with high
winds. Also known as cyclones and
typhoons Form in the tropics Created by rising warm water
vapor from warm ocean water. Then powered by the energy
released from water vapor condensing into clouds
Weather maps Produced by meteorologists to help
forecast weather. They use many variables
–Precipitation and cloud cover–Wind speed-Air pressure (isobars)– fronts
Climate Average weather
condition over many years for a particular region.
It is not measured day by day.
Climate Affected By:
1. Latitude (closeness to equator) Angle at which the sun hits Earth
2. Cycling of seasons and season Length
The tilt of the earth’s axis as it travels a revolution around the sun is the reason that we have seasons.
3. Yearly rainfall4. Topography (type of land)
Elevation, amount of water, mountains or flatness
