characteristics of the atmosphere 18-1. layers of the atmosphere earth’s atmosphere began to...
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Characteristics of the Atmosphere
18-1
Layers of the Atmosphere
Earth’s Atmosphere began to develop about 4.4 billion years ago.– Earth’s surface cooled and formed a crust.
Out-gassing, primarily from volcanoes, released the gasses that made up the primitive atmosphere (NH3, CH4, CO2, CO, H2O, N2).
Additional water was added to the planet by icy comets that struck the surface of the Earth.
Layers of the Atmosphere
About 2.5 billion years ago, the earliest forms of plant life evolved. – These organisms were capable of photosynthesis,
and oxygen gas (O2) was slowly added to the atmosphere.
Photosynthesis
CO2 + H2O X sunlight = C6H12O6 + O2
(carbon dioxide + water X sunlight = sugar + oxygen)
Layers of the Atmosphere
Photosynthesis Gas in the air
Layers of the Atmosphere 350 million years ago, oxygen gas reached levels
similar to what they are today (approximately 21% oxygen).
Present atmosphere has four primary layers that are distinguished by changes in temperature and pressure as altitude increases.
1. Troposphere: 10 miles high; all weather ; most dense 2. Stratosphere: from 10 to 30 miles; ozone layer 3. Mesosphere: from 30 to 50 miles; middle layer - Ionosphere: where auroras are made 4. Thermosphere: from 50 to 300 miles; very hot - Exosphere: from 300 to ?; the outer layer of the
thermosphere
Atmospheric Layers
Layers of the Atmosphere
The Oxygen/Carbon Dioxide Cycle - the processes by which plants and animals share and exchange oxygen and carbon dioxide.– Plants take in CO2 during photosynthesis and
produce O2 as a by-product.
– Animals (aerobic, Oxygen-breathing organisms) take in O2 during respiration and produce CO2 as a by-product.
This has kept the level of Oxygen stable in our atmosphere.
Layers of the Atmosphere
Respiration
C6H12O6 + O2 CO2 + H2O
(sugar + oxygen yields carbon dioxide + water)
All mammals carry out this process to breathe
** Plants also release water vapor through transpiration
Layers of the Atmosphere The Greenhouse Effect - caused by the
absorption of the Sun’s heat by the greenhouse gasses (mostly CO2, H2O,) in the atmosphere.
– These gasses trap heat near the surface of the planet helping to keep it warm (like blankets).
– There has been a huge increase in the amount of CO2 in our atmosphere mostly due to the burning of fossil fuels (gas, oil, coal, etc.) during the last century.
Layers of the Atmosphere
Layers of the Atmosphere
This has resulted in global warming, or too much heat energy being trapped by the atmosphere.– Increases in the Earth’s average temperature could
bring about major changes on our planet: Polar icecaps could melt, raising ocean levels. Weather patterns could be changed causing severe
droughts and floods to occur. The ocean currents could slow or stop, bringing on the
next ice age.
Exit Slip
How old is Earth? When did the atmosphere begin to form? When did today’s oxygen levels become established?
Compare and Contrast Earth’s atmosphere today compared to 4.4 billion years ago.
Do Now
What are shooting stars? How was Earth’s atmosphere different when
it was first created compared to today? What was responsible for putting oxygen
into our atmosphere? In your own words, describe the
oxygen/carbon dioxide cycle and its importance to plants and animals.
Layers of the Atmosphere
Temperature inversions occur in the troposphere Cooler air gets trapped beneath a layer of warmer air. – This shuts down the natural convection processes
and the lower air cannot rise.– We live in an area where this inversion layer
regularly occurs.
Layers of the Atmosphere
Our valley is surrounded by mountains and deserts. Cooler ocean air, carrying pollutants from the Los Angeles area, gets trapped by the mountains and a layer of warmer air above.
Layers of the Atmosphere
Ozone gas (O3) - formed when oxygen (O2) molecules are split by UV (ultraviolet) radiation in the Stratosphere.– The split oxygen, now just O and O, collide with
regular O2, and form O3.
– The Ozone layer that has formed in the stratosphere absorbs much of the dangerous UV radiation and protects us from its harmful effects.
Layers of the Atmosphere
Chlorofluorocarbons (CFC’s), a man-made chemical pollutant, reacts chemically with Ozone molecules and destroys them. – Now, dangerous UV radiation can reach the surface
of the Earth, leading to more eye problems and skin cancer.
Exit Slip
Draw and label the layers of the atmosphere.
What are CFC’s and why are they bad for the environment?
Do Now
What is the significance of the ozone layer? What is happening to deplete it? Can it be fixed? How?
Explain how carbon dioxide in the atmosphere relates to the greenhouse effect.
How is ozone formed?
Water and Wind
18-2
The Water Cycle
The atmosphere is like an “ocean of air”. We live on the bottom of this ocean in the troposphere. – The pressures, temperatures, and water in this
layer of atmosphere interact in different ways to create precipitation, winds, weather, and climate.
– The Water Cycle - describes how water molecules continuously move or recycle on our planet.
The Water Cycle
The Water Cycle We will start the water cycle at evaporation -
(water is changed from a liquid to a gas) – Evaporation - adding enough heat energy to liquid
water to allow molecules to escape from its surface and become water vapor in the atmosphere. The source of this heat energy is the sun. Humidity, or the amount of water vapor in the air, is
determined by the temperature of that air.
EXAMPLE: the warmer the air, the more water vapor it can hold (and vice versa)
The Water Cycle Relative humidity - a measure of how much
water vapor is present versus how much could be present.
Condensation - when the temperature of water vapor decreases as heat energy is lost in air and water molecules condense back into liquid droplets on the surface of a solid particle. – results in clouds, fog, or dew formation.
The Water Cycle
Precipitation - the result of the condensation droplets coming together to form larger drops that are pulled back to Earth as either rain, snow, or hail.
Precipitation enters one of the many reservoirs for water on our planet where it can be held for a very short or very long time before it evaporates and starts the cycle again.
The Water Cycle Examples of reservoirs:
– Ice and/or snow: polar icecaps, glaciers, seasonal snows, etc.
– Surface waters: lakes, ponds, rivers, streams– Ground waters: Underground aquifers– Oceans and seas: the largest source of evaporation
SEE: WATER CYCLE HANDOUT
Exit Slip
In your own words, describe the water cycle. How can pouring harmful chemicals down
the gutter have an effect on the water cycle as a whole?
Using the terms humidity and dew point explain why you might find small droplets of water on your lawn in the morning.
Do Now
What are the different sources of water?
Cloud Formation and Types Clouds - formed when warm (less dense) air
rises and water vapor condenses as it cools.– occurs in the troposphere
Clouds are named based on shape and altitude 1. High clouds start with “cirrus” or “cirro-” 2. Mid level clouds start with “alto-” 3. Low level clouds have no prefix 4. Clouds that have precipitation have
“nimbo” or “nimbus” in the name
Cloud Formation and Types Cirrus – high, thin, wispy clouds, 4-7miles
above earth.
Cloud Formation and Types Stratus – gray to white, sheet like and layered
clouds, 2-4 miles above earth.
Cloud Formation and Types Cumulus – fluffy columns with flat bottoms, low
to high altitude
Cloud Formation and Types
Cloud Formation and Types Combinations of the 3 clouds give you many
more types of clouds. EXAMPLES
a. Nimbostratus – rain clouds
b. Cumulonimbus – thunderstorm clouds
Cloud Formation and Types Clouds scatter some incoming solar radiation
Air Pressure
High Pressure – air molecules are close together and press down on Earth’s surface.
1. Air warms under pressure a. The Deserts and Poles Low Pressure – air molecules are far apart and
rise away from Earth’s surface.– Air cools and condenses with less pressure
The Equator and tropics
– Both measured with a barometer
Air Pressure
High Pressure vs. Low Pressure
Air Pressure Some scientific laws explain the relationship
between temperature, pressure, and volume in gasses.
P T V
. . . There is a relationship between all three of
them. EXAMPLE: By holding the volume (V) and increasing the pressure (P), you will get an increase in temperature (T) in the air.
Air Pressure These changes in pressure, temperature, and
volume have a dramatic affect on the water molecules (vapor) in the air.
Exit Slip
What is the relationship between air pressure, temperature and clouds?
Do Now
What type of clouds are low lying, grey, rain clouds?
What type of clouds bring thunderstorms? What altitude would you expect cumulus
clouds to be at in July? In December?
Wind
Differences in high and low pressure create wind, or moving air– Pressure gradient – when air pressure varies from
one place to another. air always moves from areas of high pressure to low
pressure.
Wind
Santa Ana Winds
WindSea Breeze
Wind Earth’s rotation also affects wind direction.
– Winds all over the world are deflected because of Earth’s rotation.
– Coriolis Effect – the change in the direction of an object’s path due to Earth’s rotation.
Wind
N. POLE: Cold & DryMIDLATITUDES: Cool & Wet30 NORTH: Hot & Dry DesertsEQUATOR: Hot & Wet30 SOUTH: Hot & Dry DesertsS. POLE: Cold & Dry
Do Now
Why are winds patterns forever changing? What are the three steps in the water cycle? Determine whether wind moving southward
from the equator will curve eastward or westward due to the Coriolis Effect?
Describe a cumulus cloud
Weather and Climate
18-3
Weather Weather - a set of atmospheric conditions
found at any given time or location, that changes daily.– It includes a variety of short term changes in
temperature, pressure, humidity, and wind direction.– These changes are related to the development and
movement of air masses.– The storms that develop move on fast moving, high
altitude “rivers” of air called the jet stream.
Weather Meteorologists - scientists who study weather.
– they try to predict the effects on the weather by tracking the interactions between pockets of warmer or cooler air masses.
– When two air masses with different densities meet (warm vs. cold), they do not mix. Instead, they form a boundary or front. Stormy weather is often associated with a strong frontal
system.
Weather A warm front forms as a warm air mass (less
dense) moves into and over a slower moving cooler air mass.– The rise of the warm air can cause Stratus clouds
with moderate to light rains or drizzles.
Weather A cold front forms as a cold air mass (more
dense) moves into and under a slower moving warm air mass.– This creates a steep edge to the front and force the
warm air to rise very quickly creating Cumulonimbus clouds with heavy rains, or hail, as well as thunder and lightening plus wind.
Weather A stationary front occurs when two air masses
meet but neither is displaced. – Instead, the air masses move side by side creating
weather conditions similar to those near a warm front.
Weather Severe weather can arise during stormy
weather conditions and can be some of the most dangerous natural phenomena on Earth. – Lightning - a giant electrical “spark” or discharge
that can occur in a cold front (thunderstorm). Strong up-drafts force water droplets to collide with
larger drops creating an opposite charge in the top and bottom of the cloud.
A “giant spark” will jump between the two to equalize them; the heat generated is tremendous and the rapidly expanding air creates a sonic shock wave called thunder.
Weather
Just like in air pressure, lightning
wants all of the charges to be
balanced
Exit Slip
What is a front? What results from two fronts meeting?
Describe lightning
Do Now
Compare and contrast a warm front, a cold front, and a stationary front
Weather Tornadoes - high-speed, rotating winds that
extend to the ground from thunderclouds in cold front conditions.– Quickly rising warm air from the Gulf of Mexico
comes in contact with the cold jet stream from Canada and rotates creating a funnel cloud. A funnel cloud that reaches the ground (tornado) can
suck up objects through its center. Damage from strong winds of over 300 miles per hour. Happen most often in the Midwest
Weather Funnel clouds that touch down over water are
called water spouts.
WeatherTornado Damage
Weather Hurricanes/Cyclones/Typhoons
– Hurricanes – large circulating masses of clouds, wind, and rain about 375 miles wide.
Formation– Start as tropical depressions (an area of intense low
pressure).– Then become a tropical storm.– Finally, when winds are at least 74 mph and the
system spins, it is a hurricane.
Weather Hurricanes are driven by warm waters and the
condensation of water vapor. Damage
– high winds and storm surges
WeatherHurricane Damage
Climate Climate – the general weather conditions over
many years, or the average of the weather Climate is affected by latitude, seasons, and
elevation.– Temperatures are warmer near the equator.
Solar energy is more concentrated there, than at the poles.
Sun rays hit vertically year round.
Climate
Climate Earth’s tilt is why we have seasons We are tilted towards the sun in summer, and
away from the sun during winter.
Climate Topography, or the surface features on Earth
affect climate.– Mountains create rain shadow deserts like the
Mojave Desert
Climate Climate changes over time
– Climatic regions change as the continent move.– Ice ages have come and gone various times.– The planet has warmed in the past too– Tree rings, ice core samples, and ocean floor
samples tell us this.
Exit Slip
Describe how the rain shadow effect works. How is a hurricane formed? How is a tornado formed? What front is required for major weather to
occur?