Transcript Atmospheres

Ch. 22 The Atmosphere
• The layer of gases that
surround the Earth or a
mixture of gases that
surrounds a planet.
• Protects us from most of
the sun’s harmful
radiation
• Regulates the
temperature of Earth’s
surface
Composition of the Atmosphere
• Air = a mixture of gases (elements and compounds),
liquids, and solid particles
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•
Nitrogen = 78%
Oxygen = 21%
Argon = 0.9%
Carbon dioxide = 0.04%
(400 PPM)
Nitrogen
Oxygen
• 78% N₂
• 21% O2
• The biological processes of
Photosynthesis and Cellular
Respiration
move oxygen from the
atmosphere to living
organisms and back to the
atmosphere.
• Forest fires, the burning of
fossil fuels, and the
weathering of some rocks
also remove oxygen from air.
• Oxygen is necessary for
making ATP, the energy
source of cells.
• Nitrogen cycle - moves
nitrogen from the air
to the soil (bacteria),
then to plants and
animals, and then
back to the air.
• Nitrogen is necessary
for creating DNA
(nitrogen bases) and
proteins (amino
acids).
Water vapor
• Gaseous water H2O(l)
• Varies depending on time of
day, location, and season.
• Both biological
(transpiration, which is
evaporation from plants)
and geological
(evaporation) processes can
add water vapor to the
atmosphere.
• Both condensation and
precipitation can remove it.
Ozone
• O3 - a gas made of 3
Oxygen molecules.
• Forms the ozone layer
• Absorbs or reflects harmful UV
(ultraviolet) radiation from the
sun.
• Chlorofluorocarbons (CFC’s)
destroy ozone particles by
breaking them apart.
• CFC’s were originally found in
the coolants of refrigerators
and air conditioners.
• Two “holes” in the ozone, one
over each pole.
• CFC ‘s were banned, it will take
years and years to recover.
Ozone hole
• UV radiation damages DNA
• This protective layer is not evenly distributed and varies with latitude
and time of year.
• In 1985, it was noticed that the ozone layer was unusually thin over
Antarctica; a similar hole exists over the Arctic.
• The thinness allows greater amounts of UV rays to reach the surface.
Think, Pair, Share
What kinds of solid
particles do you think are
found in the atmosphere?
Particulates
• Solid particles
• Volcanic ash and dust from
eruptions
• Ash from forest fires
• Microscopic organisms
• Soil or mineral particles lifted by
winds, esp. tornadoes and wind
storms
• Pollen from plants carried by the
wind
• Salt from the ocean as sea spray
evaporates
• Particles from meteors that are
vaporized as they enter and burn
up in Earth’s atmosphere
Air Pressure – decreases with altitude
Link
Atmospheric Pressure
• Gravity holds the gases of the atmosphere near Earth’s surface.
• As a result, the gases are compressed and exert a force on the
surface they are pushing down on.
• The force per unit area that is exerted on a surface by the weight
of the atmosphere.
• Atmospheric pressure is exerted equally in all directions.
• The atmosphere gets thinner at higher altitudes. The pull of gravity
decreases with height and the air molecules spread further apart
and exert less pressure on each other.
• Atmospheric pressure decreases as altitude increases.
• As temperature increases (hotter), Atm. pressure (at sea level)
decreases. Heat causes the molecules to move farther apart.
• Air that contains a lot of water vapor is less dense than drier air
because water vapor has less mass than nitrogen or oxygen; the
lighter water vapor molecules replace an equal amount of nitrogen
and oxygen, which makes the volume of air less dense.
Measuring Atmospheric Pressure
• Three units for measuring
atmospheric pressure.
• Atmospheres (atm)
• Millimeters or inches of mercury
(mmHg or inHg)
• Millibars (mb)
• Standard atmospheric pressure:
1 atm = 760 mm Hg = 1000 mb
• Average atm. Pressure at sea level
= 1 atm.
• Instrument – Barometer
Mercurial
Barometer
• Atm. Pressure pushes on the
liquid mercury in a well at the
base of the barometer.
• The pressure pushes the mercury
up to a certain height inside a
tube.
• The greater the atm. pressure,
the higher the mercury rises.
Aneroid
Barometer
• More commonly used
• Contains a sealed metal container
that has had most of the air
removed to form a partial
vacuum.
• Changes in the atm. Pressure
cause the metal container to
bend inward or bulge out.
• These changes move a pointer on
a scale.
• Can also be used to measure
altitude above sea level altimeter.
• Since higher altitudes have lower
pressures, a lower pressure
reading can be interpreted as an
increased altitude reading.
4 Main Layers of the Atmosphere
• Show distinctive
temperature
changes with
increasing
altitude.
• Temperature
differences
mainly result
from how solar
energy is
absorbed as it
moves through
the atmosphere.
Troposphere
• Closest to the Earth’s surface
• Extends from the surface to
approx. 12 km above the
surface
• Nearly all weather occurs
here
• Almost all water vapor and
carbon dioxide is found in
this layer
• Temperature decreases as
altitude increases.
(air is heated from radiation
off the surface)
• Tropopause
• 12 km above surface
• Boundary between
troposphere and stratosphere
• Temperatures stop decreasing
Stratosphere
• Extends from the tropopause to
50 km above the surface
• Contains almost all of the ozone
(ozone layer)
• Jet airplanes usually fly here
• Temperature increases as
altitude increases
– due to heat being absorbed
by the ozone layer
- Lower stratosphere = -60oC
- Upper stratosphere = 0oC
• Stratopause
• boundary between the
stratosphere and the
mesosphere.
Mesosphere
• approx. 50 km to 80
km above the surface
of the Earth.
• Temperature
decreases as altitude
increases
• the upper boundary of
the mesosphere:
temperature = -90oC
(the coldest temp.
in the atmosphere)
• Mesopause
– the upper boundary of
the mesosphere
– temperature = -90oC.
Thermosphere
•
•
•
•
•
Extends 80 km outwards
Temperature increases as altitude
increases.
– Warmer, due to the absorption of
solar radiation by nitrogen and
oxygen atoms
– Temperatures = 1,000oC +
Air particles are very far apart.
Ionosphere
• Lower region of thermosphere,
• 80 – 400 km
• Gases absorb solar radiation
causing the atoms to lose electrons
and to produce ions and free
electrons – create the auroras.
Exosphere
• Outer region of the thermosphere,
extends for 1000’s of km.
• Spacecrafts orbit here
• Blends with the complete vacuum
of space.
Aurora Borealis
• A glow in the night sky produced in the upper
atmosphere by ionized particles from the solar
wind interacting with Earth’s magnetic field
• Earth’s atmosphere is heated
– Mostly by the transfer of energy from the
sun
– Some absorption of the sun’s rays by
gases in the atmosphere
– Some heat enters the atmosphere
indirectly as ocean and land surfaces
absorb solar energy and then give off that
energy as heat
Radiation - travels at 300,000 km/s
• Refers to all energy that travels through space as
waves (Electromagnetic Spectrum).
The Atmosphere and Solar Radiation
Solar Radiation
• When solar energy reaches the surface, it is
either absorbed or reflected
• depends on color, texture, composition,
volume, mass, transparency, state of matter,
and specific heat of the material on which the
radiation falls
• The sun’s intensity and amount of time it is
shining also influence how much energy is
absorbed or reflected.
Albedo
• The fraction of the solar radiation that is reflected
by a particular surface is called the albedo.
• 30% of the solar radiation that reaches Earth is
reflected (Earth has average albedo of 0.3 or 30%)
Absorption
• All radiation with wavelengths shorter than visible light
are absorbed by molecules of N and O in the
thermosphere and mesophere (x-rays, gamma rays and
UV rays).
• In the stratosphere, UV rays are absorbed and act upon
Oxygen to form Ozone.
• Most of the waves that reach the lower atmosphere
(visible, infrared) have longer wavelengths.
• Infrared is absorbed by carbon dioxide, water vapor
and other complex molecules in the troposphere.
• Very little visible light is absorbed as it passes through
the atmosphere.
Scattering
Scattering is what
makes the sky
appear blue and the
sun appear red at
sunrise and sunset.
• Clouds, dust, water droplets, and gas molecules
disrupt the path of radiation and cause scattering.
• Scattering occurs when the rays are reflected and
bent so that the waves travel in all directions;
some rays go back out into space and some
continue towards Earth’s surface.
• As a result, sunlight hits the Earth from all
directions.
Absorption and Infrared Energy
• When rocks, soil, water and other surface materials
absorb solar radiation (short wave infrared and visible).
These materials get warmed.
• The heated materials convert the energy into infrared
waves of longer wavelengths and reemit them back
into the air.
• Water vapor and carbon dioxide in the atmosphere
absorb these rays.
• This absorption heats the lower atmosphere and keeps
Earth’s surface warmer than it would be if there were
no atmosphere (Greenhouse Effect).
• .
Global Warming
• Generally, the amount of solar radiation
entering Earth’s atmosphere equals the
amount escaping.
• However, human activities (burning of fossil
fuels) as well as natural causes are changing
the balance and are causing the average
temperature of the atmosphere to increase.
Latitude and Season
• Latitude is the primary factor that affects the amount of
solar energy that reaches any point on Earth’s surface.
• The earth is a sphere, the sun’s rays do not strike all areas
at the same angle.
• At the equator, it hits at nearly a 90o angle, but at other
areas it is spread out (shallow angle) and is not as intense.
• Temperature varies seasonally because of the tilt of
Earth’s axis.
• As Earth revolves around the sun once each year, the
portion of Earth’s surface that receives the most intense
sunlight changes.
• Tilted toward the sun, more intense and hotter
temperatures; tilted away, less intense, lower temperatures
SEASONS
Temperature Inversions
• An atmospheric condition when warm air (less dense)
traps cool air underneath it
• Temperature inversions can make pollution worse by
trapping polluted air near the surface of the earth.
• Air pollutants – any substance in the atmosphere that
is harmful to living organisms.
• Main source of air pollution – burning of fossil fuels
(sulfur dioxide gas, hydrocarbons, nitrogen oxides,
carbon monoxide, lead, etc.)
• Smog results (smoke and fog)
RADIATION
CONDUCTION
CONVECTION
Conduction
• Involves the transfer of
heat energy through
matter by direct contact.
– Heat causes molecules to
move faster.
• A conductor is a material
that can transfer heat.
– Air is a poor conductor.
• Only the lowest levels of the
atmosphere are heated by
conduction (from contact
with the earth that has
been heated by sun via
radiation).
Convection
• Involves the transfer of heat
energy within a liquid or gas
through the motion of the liquid
or gas caused by density
differences.
• As air is heated by radiation or
conduction, it becomes less
dense and rises (pushed up by
adjacent cooler air) the cooler air
becomes warmer and rises. As
the warm air rises it cools – being
more dense it sinks (convection
cell).
– Warm air exerts less pressure so
the atmospheric pressure is lower
beneath a warm air mass.
• As dense, cool air moves into a
low pressure region (warmer air),
the less dense warmer air is
pushed upward. These pressure
differences create winds.
Winds
• Winds are produced from
differences in air pressures
• Air moves from high
pressures to low pressures.
• Winds are named for the
direction from which they
blow (where they originate)
– Prevailing Westerlies blow
from the WEST.
– Polar Easterlies blow from the
EAST.
Instruments
• A wind vane
measures wind
direction
• An anemometer,
with spinning
cups, measures
the speed of
wind.
Beaufort Scale
Measures relative
Wind speed and force.
The Coriolis Effect
• The tendency of a moving object to follow a curved path
rather than a straight path because of the rotation of Earth
(winds and ocean currents).
• The farther a wind travels, the more it is influenced by the
Coriolis effect.
• The faster an object travels, the greater the Coriolus effect.
– Each point on Earth makes one complete rotation every day;
points near the equator travel farther and faster in a day than
points closer to the poles.
– When air moves toward the poles, it travels faster than the land
beneath it; due to rotation the air appears to follow a curved path.
• Objects are deflected to the right in the Northern
hemisphere and to the left in the Southern hemisphere.
Global Winds
• Move across the Earth’s surface.
• Curve due to the Coriolis effect.
• Winds always move from high to low
pressures.
– High pressure regions tend to form where colder
air sinks
– Low pressure regions tend to form where
warmer air rises
Wind Belts
Trade winds : 0o – 30o North and South Latitude
• Flow toward the equator.
• Northern hemisphere – Northeast trade winds
• Southern hemisphere – Southeast trade winds
Prevailing Westerlies: 30o – 60o N and S Latitude
• Flow toward the poles
• Blow throughout the contiguous United States
Polar Easterlies: 60o – 90o N and S Latitude
• flow toward the equator
Wind Cells
• Air masses that do NOT move across the surface
but move upward (away from Earth’s surface) due
to convection caused by warming (convection
cells).
Doldrums: at 0o (equator)
• In this warmer, low pressure air zone most movement
is upward (rising).
• Surface winds are weak and variable.
• Tropical storms are formed here.
Horse Latitudes: at 30o N and S Latitude
• In this cooler, high pressure air zone most
movement is down toward the surface
(sinking).
• Surface winds are weak and variable.
Jet Streams
• Circle the globe
• In upper troposphere
• A narrow band of
strong winds
• POLAR JET STREAM
• Affects the U.S.
• For the East Coast,
brings in weather
systems from the west
• Can bring in colder air
from the North.
• SUBTROPICAL JET
STREAM
Local Winds
* blow over a limited (smaller) area
* Local temperature variations cause local winds
* Land surfaces heat up faster than water surfaces
SEA BREEZES
LAND BREEZES
• A cool wind moving from the
cooler water to warmer land.
• During the day, the land heats
up faster than the water.
• The warm air above the land
rises and the cooler air over
the water moves to replace it.
• Sea breezes blow during the
day.
• A cool wind moving from
the cooler land to the
warmer water.
• At night, the land cools
more rapidly than the water
• Land breezes blow at night.
SEA BREEZE
LAND BREEZE
Valley Breezes
• During daylight hours, a
gentle breeze blows
upslope.
• Forms when warm air from
the valleys moves upslope.
• Days tend to be warmer.
Mountain Breezes
• At night, the mountains cool
more quickly than the
valleys do.
• The cool air descends from
the mountain peaks toward
the valleys.
• Nights tend to cool off.
Wind Chill
• The effect of the wind on temperature
• How the temperature really feels