Thursday 10/4 Agenda1. Read ORANGE lab on your table

2. Review Notes Air, Weather, Climate slides 1-153. Labs: Albedo & Greenhouse EffectHW: 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)

• compared to the size of the Earth (104 km), the atmosphere is a thin shell (120 km).

Earth’s Atmosphere

http://www.gsfc.nasa.gov/gsfc/earth/pinatuboimages.htmhttp://www.gsfc.nasa.gov/gsfc/earth/pinatuboimages.htm

• Thermosphere

– (Ionosphere)

• Mesosphere• Stratosphere • Troposphere

AtmosphereLayers

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

WEATHERPhysical 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 light- trapped 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.htmlVideos 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 Currents4. 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.school-portal.co.uk/GroupDownloadFile.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_science/terc/content/visualizations/es1904/es1904page01.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 westerly- come 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. Humidity9. Humidity

• relative humidityrelative humidity is the amount of water vapor is the amount of water vapor in the air compared with the potential amount in the air compared with the potential amount at the air's current temperatureat the air's current temperature– expressed as a percentageexpressed as a percentage

– depends on air temperature, air pressure, and depends on air temperature, air pressure, and water availabilitywater 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

CLIMATEPattern 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 cycles- periodic 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