Transcript AIR, CLIMATE, AND WEATHER

Thursday 10/4 Agenda
1. Read ORANGE lab on your table
2. Review Notes Air, Weather,
Climate slides 1-15
3. Labs: Albedo & Greenhouse
Effect
HW:
finish questions chapter 23, Action Savings
in CO2, simulation on CO2
AIR, CLIMATE, AND
WEATHER
CHAPTER 23
APES
Weather vs. Climate
• Weather
– Daily changes in the
physical conditions
of the atmosphere
(moisture, temp,
pressure, wind)
– Controlled by solar
energy which controls
winds which push
moisture & temp
around planet
• Climate
– Long term patterns
of weather in a
particular area.
– Undergo cyclic
changes over
decades, centuries,
and millenia
Past Composition of the Atmosphere
• Millions of years ago
mostly H and He
• Volcanic emissions
added C, N2, O2 & S
• Most oxygen was
produced by
photosynthetic bacteria
and algae
• Now- 78% N2, 21% O2,
1% various gases (see
chart)
Earth’s Atmosphere
• compared to the size
of the Earth (104
km), the atmosphere
is a thin shell (120
km).
http://www.gsfc.nasa.gov/gsfc/earth/pinatuboimages.htm
Atmosphere
Layers
• Thermosphere
– (Ionosphere)
• Mesosphere
• Stratosphere
• Troposphere
Troposphere
• 8 to 14.5 km high (5 to 9 miles)
• most dense
• the temperature drops from about 17 to
-52ºC
• almost all weather is in this region
Stratosphere
• extends to 50 km (31 miles) high
• dry and less dense
• temperature in this region increases
gradually to -3ºC, due to the absorption
of ultraviolet radiation
• ozone layer absorbs and scatters the
solar ultraviolet radiation
• 99% of "air" is located in first two layers
Thermosphere
Mesosphere, Ionosphere,
Thermosphere
• Mesosphere- middle layer
– -80ºC
• Thermosphere
– Ionosphere is lowest part of thermosphere
where aurora borealis appears
– 1000 miles from surface
– 500 C-200 C
Mesosphere, Ionosphere,
Thermosphere
• Mesosphere- middle layer
– -80ºC
• Thermosphere
– Ionosphere is lowest part of thermosphere
where aurora borealis appears
– 1000 miles from surface
– 500 C-200 C
WEATHER
Physical conditions of temp,
humidity, pressure, wind, &
precip.
The Great Weather Machine
• THE SUN causes global cycling of wind
and water that creates our climate and
distributes energy & material thru
environment.
1. Seasonal
Changes
• Occur because
the earth’s axis is
tilted
• Creates opposite
seasons in the
northern and
southern
hemisphere
• Factor that
determines global
air circulation
patterns
What types of radiation does the
earth get?
• Visible light- comes
thru undiminished
• Ultraviolet lighttrapped by ozone
layer in stratosphere
• Infrared radiation
absorbed by CO2 and
H2O in troposphere
2. SOLAR RADIATION
•
•
•
•
Incoming energy
Insolation- absorbed sunlight
Albedo- reflected sunlight
Earth’s insolation & albedo:
– Surface & oceans absorb 50%
& reflect 4%
– Clouds absorb 3% & reflect
20%
– Atmosphere absorbs 16% &
reflects 6%
– Bottom line:
• 70% absorbed
• 30% reflected
http://www.epa.gov/hiri/about/videos.html
Videos on Heat Island Effect
Quickwrite
• 1. How does the heat island effect form?
• 2. Which surfaces have high albedo?
Why?
3. THERMAL RADIATION
• Outgoing energy
• Mostly infrared radiation
• Can be reradiated from
surface, clouds & atmosphere
• Longer wavelengths absorbed
by GASES in lower levels of
atmosphere, trapping heat
close to earth’s surface
• This phenomena is called the
“greenhouse effect”
• Our planet would be too cold to
live on if we didn’t have the
greenhouse effect.
4. Ocean Currents
• Sea-surface temperature
influences air temperature as
the ocean exchanges heat with
the overlying atmosphere.
• It also influences evaporation
rates which are generally higher
where sea-surface temperature
is higher
5. Convection Currents
• Sun heats earth’s surface
• Some heat transferred to
air layers
• Air expands & becomes
less dense
• This lighter air rises & is
replaced by cooler,
heavier air resulting in
vertical convection
currents
• http://www.schoolportal.co.uk/GroupDownl
oadFile.asp?File=39949
Convection Currents
• At the Equator- solar energy is
intense- comes straight down
so energy is high- creates
energy surplus
• At the Poles- solar energy
comes in at an angle so much
energy lost from absorption
thru long columns of air. Also,
tilt of earth’s axis means no
sunlight during much of winter
• This energy imbalance is
evened out by mvmt of air &
water vapor in atmosphere &
by liquid water in rivers &
oceans.
http://www.usatoday.com/weather/tg/wglobale/wglobale.htm
6. Coriolis Effect
• Coriolis effect- Effect
of earth’s rotation on
wind direction
• http://www.classzone.
com/books/earth_scie
nce/terc/content/visua
lizations/es1904/es19
04page01.cfm
Coriolis Effect
• Since winds are just molecules of air, they are also
subject to Coriolis forces.
• Winds are basically driven by Solar heating.
• Solar heating on the Earth has the effect of
producing 3 major convection zones in each
hemisphere.
• If solar heating were the only thing influencing the
weather, we would then expect the prevailing winds
along the Earth's surface to either be from the North
or the South, depending on the latitude.
• However, the Coriolis force deflects these wind
flows to the right in the Northern hemisphere and to
the left in the Southern hemisphere.
7. Jet Streams
• Two major ones in N.
Hemisphere
– Midlatitude- just below
the circumpolar vortex
– Subtropical- about 30º
N latitude
• Like a massive river
of air moving wind,
water, heat, etc.
• Usually westerlycome from the west
8. Air Pressure
•
caused by the weight of the air
pressing down on the Earth, the
ocean and on the air below
•
falls as you go higher
•
changes with weather
•
air in a high pressure area
compresses and warms as it
descends
•
the warming inhibits the formation
of clouds, meaning the sky is
normally sunny in high-pressure
areas
•
haze and fog might form
•
the opposite occurs in an area of
low pressure
9. Humidity
• relative humidity is the amount of water vapor
in the air compared with the potential amount
at the air's current temperature
– expressed as a percentage
– depends on air temperature, air pressure, and
water availability
10. Cloud cover
• moisture in the atmosphere forms clouds which
cover an average of 40% of the Earth at any given
time
• a cloudless Earth would absorb nearly 20 percent
more heat from the sun
• clouds cool the planet by reflecting sunlight back
into space. (Remember…This is known as Albedo)
However
• clouds reduce the amount of heat that radiates into
space by absorbing the heat radiating from the
surface and reradiating some of it back down
• the process traps heat like a blanket
11. Precipitation
• Air containing water vapor cools in
atmosphere and therefore condenses to
form droplets of liquid water
– Rain: liquid, falls, d >0.5 mm (sphere)
– Freezing Rain: occurs when drop touches
frozen surface
– Sleet: ice pellets, d < 0.5 mm, begins as rain
but enters air below freezing
– Snow: water deposits in hexagonal nuclei
below freezing
– Hail: 5-190 mm in diameter, concentric rings
of ice
12. Fronts
•
•
Boundary btwn 2 air masses of different
temp. & density
Cold–
–
–
–
–
–
•
Cooler air displaces warmer air
Cold air more dense, hugs ground &
pushes under warm air
Warm air moves up, cools, precipitates
Cool air upper layers move faster due to less
drag from the ground
Strong storms- thunderheads
Weather afterwards is clear, dry, & pleasant
Warm–
–
–
–
Less dense so will slide up over cool, air
pockets creating long wedge shaped profile
Prevents violent updrafts
Layers of clouds at different levels
Can bring days of drizzle & could skies
13. Cyclonic Storms
• Low pressure generated
by rising warm air
• Winds swirl into low
pressure area
• Rising air is full of water
vapor
• latent energy released by
condensation intensifies
• Storm cells will build as
this cycle continues
a. Hurricanes
•
•
•
•
•
•
•
Atlantic & E. Pacific- hurricanes
W. Pacific- typhoons
Indian Ocean- cyclones
Winds as high as 200 mph
cause most property damage and loss of life
begin over warm oceans of the tropics
solar insolation (water >80ºF) provides
energy for huge evaporation, cloud
formation, and atmospheric lifting
b. Tornadoes
• swirling masses of air with speeds of 300 mph+, may
have hail
• waterspouts occur over water
• center of tornado is extreme low pressure which causes
buildings to implode
• Faster moving upper air speeds, lower speeds close to
ground cause rotation
• destruction is usually less than 0.5 miles wide and 15
miles long
• Tornado Alley is from Texas to Indiana
– Cold air from Canada collides with warm air from Gulf of Mexico
• Downbursts are less organized air masses but very
strong
c. Seasonal Winds
• Monsoon- seasonal reversal of wind
patterns caused by different heating &
cooling rates of ocean & continents
– Cause massive amounts of rain & flooding
– Common in India due to India’s geography
– Also in N. Africa
CLIMATE
Pattern of weather in a region
over long time period
Climatic Catastrophes
• Can be drastic- (Ice Age) entire
communities can be destroyed, species
can become extinct
– 65 million years ago- Cretaceous- 75% of
life (including dinosaurs) became extinct
due to sudden cooling of atmosphere
(Sulfur dioxide from volcanoes?)
• Can be gradual- allows population to
become adapted or migrate
Patterns in Weather Cycles
• Milankovitch cyclesperiodic shifts in earth’s
orbit and tilt
– Orbit stretches & shortens
every 100,000 years
– Axis of rotation changes
angle of tilt every 40,000
years
– Axis wobbles like a top
every 26,000 years
• These variations change
the distribution & intensity
of sunlight
• Evidence of this in
sedimentary rock layers
Patterns in Weather Cycles
• 1400’s- “little ice age”
– Temps dropped, crops failed
– Fish did not migrate north
– People starved or killed by
Inuits forced south due to cold
• 135,000-115,000 years ago
temp. flipped from warm to
cold over a period of decades
instead of centuries
– Scientists think might be due
to shift in ocean currents or
dilution of ocean with
freshwater
– Or volcanic eruptions
El Nino Southern Oscillations
(ENSO)
• Occurs every 2-7 years
• Occurs when prevailing westerly winds cease or
slow down allowing surface of ocean to warm up.
• Warmer waters drive schools of fish away affecting
South American fishermen
• El Nino- means “Christ child” because it happens
around Christmas in Peru
• La Nina- means “little girl” represents time when El
Nino is not occurring.
• These two cycles are called the El Nino Southern
Oscillation or ENSO
How does ENSO affect us?
– Northern jet stream is split & drawn over
Southern U.S.
– This pulls moist air from Gulf of Mexico up
causing more intense storms & heavy rain
– La Nina has opposite effect causing hot, dry
weather