Unit 6
Chapter 19
The Atmosphere
Meteorology – the study of the atmosphere
Meteorologist – the person that people think can’t tell the weather.
But they really try.
The atmosphere is the gaseous layer that surrounds the Earth. It is
made up of chemical elements that protect the earth from the
sun’s radiation while providing us with a climate that will sustain
life.
See page 1 ESRT
Remember:
Early atmosphere came from the volcanoes
CO2, SO2 , H20, N2
Then sunlight split the water molecules into hydrogen and water.
Then photosynthesis kicked in.
Today our Air is:
78% N2
21% O2
<1% Ar
CO2
He, H2, Ne, O3 (Ozone)
And other particulates and pollutants
The % of Nitrogen and Oxygen stays constant up to 80km
Nitrogen makes up about 78% of the Earth’s Atmosphere. Nitrogen is
added to and removed from the Atmosphere through the nitrogen
cycle (chpt 2).
Oxygen in the Atmosphere
Oxygen makes up about 21% of the Earth’s Atmosphere. O2 is added to
and removed from the Atmosphere through the Oxygen Cycle (chpt
2).
Plants take in CO2 release O2
Animals take in O2 release CO2
Plants decompose to CO2
H2OV is released in evapotranspiration & exhaling
Water leaves by way of precipitation
This stays in a semi-balance. However the levels of CO2 maybe on the
rise according to the Mauna Loa Observatory in Hawaii which has
been monitoring it from 1959 – Present.
Water Vapor (H2O(v), H20(gas)) is present in most air but the percent
changes constantly. It is highest near the surface and then lower
as you go up in altitude.
Dry Air has less than 1% water vapor which in turn has a higher
pressure reading.
Moist Air has approximately 4% water vapor which has a lower
pressure reading.
The more water vapor in the atmosphere, the lower the pressure is.
Water weighs less than oxygen, therefore, the more water in the
air, the lower the pressure.
Ozone (O3) in the upper atmosphere absorbs harmful UV Rays.
Chlorofluorocarbons (CFC’s) – reduce the ozone in the air therefore
increase the ultraviolet light reaching the surface (us). CFC’s can
come from coolants, foam products and cleaning supplies for
electronic components.
The most common particulates are
Volcanic Ash, dirt/dust, pollen and salt from sea spray.
Others are:
Air Pollution:
An Air borne gas or particle that occurs at a concentration that is capable of harming humans.
In 1970 the Clean Air Act was passed. It tried to limit the amounts of CO, NO2, SO2,
particulate matter, pb (lead) and O3 that were being released into the atmosphere.
Acid Rain
SO2 or Nitrogen Oxides react with water causing the levels of acid in the precipitation to rise.
Acid is measured on the pH scale.
pH scale: 10 times more acidic than the number before.
more acidic the rain is.
The lower the pH number the
Can do more harm than anyone thinks. It is harmful to lakes, streams and forests. It will
roughen surfaces and remove the delicate carved details.
Smog
The term was made in the early 1900’s. It refers to the smoky fog in London. Now it means
the photochemical smog. Because smog is so thick it can create weather conditions that
are very unique, one is temperature inversion.
Gravity holds the gases down, the molecules get compressed and exert a force
on the Earth’s surface. The pressure exerted is called the atmospheric
pressure. It is exerted equally in all directions.
We say “light as air” but air is not really light. From the top of the
atmosphere to sea level it is approximately 14.7 pounds per square inch
(yep this is on top of you too).
Think about this, when you stretch your hand out palm up, we don’t even
think about any pressure being on it. We don’t feel it, therefore, we don’t
think it’s there. We have pressure pushing down on our hand, while
pressure is pushing up and out. This keeps us in balance so we can
perform our daily stuff. An astronaut and submariner need to pressurize
their environment to be the same as normal.
Pressure decreases as elevation increases. Air pressure decreases about 50
percent for every 5 km increase in elevation.
Mile High Stadium (Denver) is 1.6 km above sea level; pressure is about
82% than at sea level (approx 18% decrease).
Keep in mind. A molecule of water will weigh less than a molecule of “air”.
The more water in the air, the lower the pressure.
Mercurial Barometer
The more air pressure the higher the Hg moves up the tube lower air
pressures allow the Hg level to drop
An aneroid barometer uses a metal capsule to measure the pressure
changes. It operates in the same manner as a seismograph.
Troposphere
Lowest Level of the Atmosphere
Contains approx 80% of the total mass
All weather occurs in this layer (water vapor)
Most small jets fly in this layer
Temperature decreases as you increase altitude.
Most air temperature decrease approx. 6.5OC per km
Tropopause
The interchange between the troposphere & stratosphere
At equator it is approximately 16km
At the poles it is approximately 9km
The jet stream is located just below the pause.
Stratosphere
Height of approx 50km
No water in this layer so it is clear & dry
About as cold as the tropopause- but warms as
you go up.
Contains ozone layer which absorbs UV Light
Large jets fly here
Strong steady winds
Stratopause
The boundary between the stratosphere and mesosphere
The Mesosphere
Mesosphere
Between 50 – 90 km
Temperatures drop as you increase altitude
Mesopause
The boundary between the upper mesosphere and thermosphere
The Thermosphere
Thermosphere
About 90km
Atmosphere is extremely thin
Temperature can rise to about 1000oC
Separated into layers of gases
Heavier – lower (nitrogen)
Middle – Oxygen at approx 1000km
Higher – lighter (Helium) approx 2400km
Highest – lightest (Hydrogen)
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Ionosphere
A layer of the atmosphere containing Ions (Charged atoms)
The ions are deflected by the magnetic field to the North and South Poles. They interact with air molecules
to form auras.
Radio waves are reflected in this layer causing waves to travel further when the solar flares occur. TV
waves need to be captured by satellite and bounced back to earth.
The Exosphere
Exosphere
It is the last layer of the atmosphere, truly outer space.
Normally as altitude increases, temperature decreases. In a
temperature inversion the temperature at the surface is cooler than
at higher altitudes. On clear dry nights – the surface and air just
above the surface cools quickly. The land cools faster than the air
which cools the air even more up to a few hundred meters. Cool
or cold air is denser than warm air so this air can get trapped
under warm air. This can trap pollution in the air near the surface
and cause health problems. Strong winds or strong sunlight can
destroy temperature inversions.
The Earth is heated by the transfer of energy from
the sun either directly or indirectly.
Heat energy enters and moves through the
atmosphere in 3 ways:
Radiation, Convection and Conduction
Radiation is the transfer of energy in the form of visible light, ultra
violet rays and other forms of electromagnetic energy. It does not
require a medium, making it the only way energy can travel
through space.
Insolation – Incoming Solar Radiation
Sunlight
Source of most heat on the earth and in the air
As long as heat budget is in balance, earth is OK. Out of
balance: It can either heat up (Global
Warming**), or cool down (Ice Age).
Scattering
Clouds, dust, water droplets and gas disrupt the path of the radiation.
The scattering makes the sky appear blue during the day and red
at sunset.
Reflection
The amount of sunlight (solar energy) can either be absorbed or
reflected. The characteristics of the area will determine whether it
is reflected or absorbed.
Albedo
It is the fraction of the solar radiation that is reflected by a
particular surface. Because 30% of the insolation is already
reflected, we are considered a 0.3 albedo.
The sun’s energy that reaches us is absorbed by rocks, soil, water and
other surface materials. The short wavelengths (infrared and
visible light) heats up the surface when the surface absorbs the
radiation. It then re-emits the energy at longer wavelengths. Gas
and water vapor absorbs these rays which heats up the lower
atmospheric layers. This keeps the Earth nice and warm.
It can bend the light rays and produce a mirage too.
The greenhouse effect occurs when infrared radiation remains in
Earth’s atmosphere. Usually insolation has short wavelengths; it
can easily pass through the atmosphere, infrared radiation has
longer wavelengths and cannot leave the atmosphere as easily.
This creates a situation that will keep re-heating the atmosphere,
bringing the temperatures up.
Water and Carbon Dioxide easily trap infrared radiation. (H20 and
CO2 are greenhouse gases)
Burning fossil fuels release C02 and H20 may be increasing the
greenhouse effect.
Actually the greenhouse effect is keeping the planet at a habitable
temperature right now.
The intensity of the sun varies with the time of day, latitude and
season (time of year). Certain materials also affect the intensity.
Time of Day:
As we know the sun is at it’s highest at solar noon. This allows for the
most intense rays of the sun to be radiated to us.
The warmest part of the day is 1 – 2 hrs after solar noon. Why?
For several hours after solar noon, the lower air still receives heat
from the sun & ground keeping in the heat.
So the coldest part of the day is just before sunrise
Why?
Latitude is the primary factor that affects the amount of solar energy.
When the amount of sunlight changes on each location, different
portions will experience different seasons.
At 90o the sun warms the earth the most
At 0o the sun warms the earth the least plus the sunlight has to go
through more atmosphere
Equator – warm – sun high in the sky
Poles – cool – sun low in the sky
Long Island – warm summer – sun high in the sky:
Cool winter – sun low in the sky
The sun is the highest in the sky on June 21 in the Northern
Hemisphere. The warmest time is July/August. The sun is the
lowest in the sky on December 21 in the Northern Hemisphere.
The coldest time is in January/February.
Cloud Cover:
More insolation is available on clear days then on cloudy days
because it is reflected back into the atmosphere.
Land heats up faster and higher than water
Land cools down faster and lower than water
Land near the oceans does not warm up as much or cools down as
much as land locked areas
Dark rough
absorbs more sunlight than light smooth surfaces
Road, forests, green fields
Light smooth
Reflects more sunlight
Water, ice, snow
Land
Ocean
Low specific heat
High specific heat
Heats up quick
Heats up slowly
Cools down quick
Cools down slowly
Sunlight penetrates
Sunlight penetrates
Surface only
many feet
Heat only moves by
Heat moves by
Conduction
conduction and convection
The heat is transferred by direct contact. It is actually the transfer of
energy through the collision of the atoms or molecules of a
substance.
Ex. Pot on the stove: Air touching warm ground.
Heat transfer by density differences. Works best with liquids and
gases.
Ex. The water in the pot boiling.
Air near the surface generally flows from the poles towards the
equator. This is because air flows from high pressure (cold) to low
pressure (warm).
High Pressure-clockwise winds
-winds blow out from the center
-called an ANTICYCLONE
Low Pressure-counterclockwise winds
-winds blow in towards the center
- called a CYCLONE
Northern Hemisphere
All movement is deflected to the right of straight-ahead
Southern Hemisphere
All movement is deflected to the left of straight ahead.
Because of the Coriolis Effect and the fact that pressure goes from
High to Low creating the wind, it gives us the direction of winds
in a High or Low.
Winds are greater near the poles
It does not depend on direction of movement (compass direction).
It is noticeable for objects (rockets, airplanes, etc) traveling over great
distances and at great speeds. Also true for wind and water
currents.
The winds are affected by friction between the air and the ground.
Friction reduces the impact of the Coriolis Effect and the surface
winds. The smoother the surface, the faster the winds, the
stronger the Coriolis Effect will be.
Higher altitude winds are not affected by the friction. At heights
about 2km the Coriolis Effect is great. This curves the winds in a
High or Low pressure.
http://www.classzone.com/books/earth_science/terc/content/visu
alizations/es1904/es1904page01.cfm?chapter_no=visualization
Some winds are predictable, while most are affected by other
variables.
Ex. Temp differences, time of year, topography
Without the coriolis effect the winds would only shift seasonally
warm air rises to polar regions in summer. Cold air moves
towards the equator in winter. This would produce one circular
cell in each hemisphere.
Both Hemispheres have 3 cells
Equator 0o – 30o
30o - 60o
60o - 90o
Caused by alternating bands of high and low pressure
60o – Polar Front – cold air moves down, warm up
30o – flows back to equator because it is high
Air blowing from the Poles is deflected to the right
90o – 60o - Easterlies
60o - 30o - Westerlies
30o - 0o – Easterlies
In the Southern Hemisphere it is reversed.
Trade Winds
Occur between Oo and 30o north or south. In the Northern Hemisphere they flow from
the Northeast. In the Southern Hemisphere they flow from the Southeast. They
were used in the 18th and 19th century for trade ships.
Westerlies
Occur between 60o and 30o. In the Northern Hemisphere they flow from the southwest.
In the Southern Hemisphere, they flow from the Northwest. They blow throughout
the contiguous United States.
Polar Easterlies
Occurs at 60o North or South of the equator. It is a zone of low pressure. The winds are
the strongest where they flow off of Antarctica.
The Doldrums and Horse Latitudes
The Doldrums are also known as the Inter-Tropical Convergence Zone. It is a low
pressure zone at the surface in the tropics due to heating. It is a place where both
hemispheres converge.
It is Hot & Humid; has little to no wind; rain is common
The Horse Latitudes are between 20o and 30o, occurs when sinking air forms a
subtropical high pressure zone. Little to no precipitation; most of the deserts are
located within this zone.
This occurs because of the shift in the position of the sun during the
seasonal changes. Different areas receive different amounts of
heating, which causes the shift in wind patterns. Some areas that
usually have Westerlies in the winter may experience a trade wind
in the summer.
The jet stream is narrow bands of swift moving winds that blow
in the upper troposphere and lower stratosphere. They
blow from the West to the East in North America (West
Winds). They can reach speeds of approximately 400 km/h.
Typically 100’s of km wide and approx 2 – 3 km thick. They
push cold dry air down from Canada in the winter – Polar
Jet Stream. They push warm moist air up from the Gulf
region in the summer (subtropical, does not change speed or
position). Not continuous around the globe.
A breeze is any wind that is less than 50 km/h.
Land and Sea Breezes
During the day land heats up and causes a low pressure
area. The water is colder (high pressure area) so air
will rush from high to low pressure, creating a wind.
At night the opposite occurs. The water will retain heat
longer so it becomes the low pressure and the land
loses heat quicker becoming the high pressure. Wind
will rush from the land to the sea.
During the day the air blows up hill because it is cooler in the valley,
the sun warms the hill first. At night the colder air blows down
slope.