AIR, W

EATHER, C

LIMAT

E

OBJECTIVES

• Summarize structure and composition of atmosphere

• Explain how jet streams, prevailing winds, and frontal systems determine local weather

• Describe how tornadoes and cyclonic storms form and why they are dangerous

• Explain how El Nino cycles change ocean surface temperatures and affect continental climate

• Understand the driving forces thought to bring about normal climatic change

• Analyze human contributions to global climate change and what affects our actions are having on physical and biological systems

• Debate policy options for responding to threats of global climate change

VOCAB

ChlorofluorocarbonsalbedoGreenhouse gasesRain-shadow effectSpecific HeatSecond law of

thermodynamicsStratospheric ozone

layerCoriolis effect

TroposphereStratosphereMesosphereThermosphereExosphereMagnetosphereConvection CurrentElectromagnetic SpectrumROYGBIV

MAIN CONCEPTS

Atmosphere

• Definitions

• Origins

• Composition

• Structure

• Function

ATMOSPHERE - DEFINITIONS

ATMOSPHERE - ORIGINS

Earliest atmosphere 4.5 bya Hydrogen H and helium He (solar origins) Water vapor H2O, methane CH4, ammonia NH3 (as in gas giant planets)

Second atmosphere 3.8 bya Asteroid collisions and Volcanic eruptions add carbon dioxide CO2, Nitrogen N2,

and inert gases

Third atmosphere – 2.7 bya Organic molecules evolve into first organisms—prokaryotes Prokaryotes evolve into “cyanobacteria” (can photosynthesize) Photosynthesis releases molecular oxygen O2. Aerosols – minute particles

MAJOR GEOLOGIC EVENTS IN EARTH’S HISTORYGeological event Billions of years

ago

Origin of Earth 4.5

Formation of oldest known bedrock 3.9

First evidence of organic matter in rocks 3.7

Photosynthesis evolves in plants 3.0

Limestone deposits become common 1.8

Many fossils of marine invertebrates 0.55

Earliest land plants 0.44

Earliest land animals 0.40

Dinosaurs dominant 0.17

CHANGES IN ATMOSPHERE OVER TIME

Billions of years before present

GAS 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 Present

CO2 80% 20% 10% 8% 5% 3% 1% 0.07%

0.04%

0.037%

N2 10 35 55 65 72 75 76 77 78 78

H2 5 3 1 0.5 0 0 0 0 0 0

O2 0 0 0 0 0 1 5 10 15 21

Other gases

5 42 34 26 23 21 18 13 7 1Set up a graph to show how the major gases of the atmosphere have changed over the past 4.5 billion years. Use a different color for each gas. The events from the previous slide should appear vertically below the X-axis.

ATMOSPHERE - COMPOSITION

DRYNitrogen N2 78%Oxygen O2 20.9%Argon Ar 0.9%Trace Gases 0.037%

(CO2 0.035%)

GREENHOUSE GASESWater vapor 0.25% by mass. Carbon dioxide CO2Methane CH4Nitrous Oxide N2OOzone O3

ATMOSPHERE - STRUCTURE

Four layers – absorb solar energy differentlyTROPOSPHERE•From earth’s surface to ~10 km•Air circulates, redistributing heat•Weather, clouds•Dense, contains water vapor•Temperature decreases with altitudeSTRATOSPHERE•From troposphere to 50 km •Ozone layer; no water vapor•No mixing – particles remain suspended•Absorbs UV-B solar radiation (protects life)•Temperature increases with altitude

STRUCTURE

Four layers, continuedMESOSPHERE•From Stratosphere to 80 km•Temperature decreases to -80 celsius•Meteors chill out here

THERMOSPHERE•Highly energized gases are ionized by solar and cosmic radiation•Aurora Borealis and Aurora Australialis occur here•1500 celsius•International Space Station orbits here

ELECTROMAGNETIC RADIATION– BACKGROUND

Electromagnetic spectrum is the term for the range of known energies in existence.

• EM spectrum ranges from very long waves (hundreds of meters) to very short waves (nanometers)

• Continuum of low energy (not harmful to humans) to very high energy (deadly to humans)

• Radio – Microwaves – Infrared waves – Visible Lilght – UV Light – X-Rays – Gamma Rays

• Visible Light is the range of the electromagnetic spectrum that can be seen by the human eye.

• It consists of waves we see as different colors – ROYGBIV

Red light ~ 400 nm Violet light ~ 700 nm

• All waves in the EM spectrum travel at a speed of 3 x 108 meters per second (m/s)

• And what is light? Energy emitted from the nucleus of an atom due to nuclear instability.

EM energy can travel through empty space, while sound and heat waves require matter to transmit energy from one place to another.

ATMOSPHERE FUNCTION

Reflects, absorbs, transmits solar radiation to Earth

• 25% reflected by clouds and gases

• 25% absorbed by greenhouse gases (traps heat)

• 50% transmitted to Earth’s surface

• The wavelength of energy (and the medium) determines if and how energy is reflected, transmitted or absorbed.

REFLECTION, TRANSMISSION, ABSORPTION

Albedo – the reflective property of a surface. For example, fresh snow and cumulus clouds have a high albedo.

Transmission and Absorption depend on the wavelength of the light.

Transmission – the process of light passing through a transparent material. Shorter wavelengths of light are transmitted through the atmosphere to Earth’s surface.

Absorption – the process of light being taken in by a surface and changing into heat energy. Longer wavelengths of light are absorbed by the atmosphere.

Albedo of specific surfaces

DEMONSTRATION – CONVECTION CELLS

Draw a diagram in your notes to show:

• The set up

• The proceedure

• The movement

Discuss with a neighbor and then summarize in your notes how this demonstration is a model for energy transfer in Earth’s atmosphere.

https://www.youtube.com/watch?v=WEDUtS0IMws

https://www.youtube.com/watch?v=GyCoyhFnnj8

https://www.youtube.com/watch?v=5QOVwX-6g-Q

FUNCTION – HEAT TRANSFER

Water vapor absorbs energy as latent heat

As water vapor condenses, heat energy is released.

Convection cells – circulation patterns of air that redistribute heat and water vapor. Hot air rises due to decreased pressure. As air rises, it cools, and falls again.

Precipitation occurs as rising air cools (cannot hold the same amount of water vapor)

FUNCTION – HEAT TRANSFER

Hot air rises, cool air rushes in to take its place = wind

CORIOLIS EFFECT

Air circulation plus Earth movement create wind pattern called Coriolis Effect

These atmospheric wind currents create climate on land and ocean water currents

OCEAN CURRENTS

Climate conditions are modified by ocean circulation

SEASONAL CHANGES

Amount of energy received depends on angle of incidence

Earth’s tilt remains the same as Earth revolves around the Sun

Earth’s tilt is the reason for the seasons

When northern hemisphere has summer (Jun-Sep) southern hemis-phere has winter.

In December when northern hemisphere tilts away from the sun, southern hemisphere tilts towards the sun.

THE IMPACT OF SPECIFIC HEAT

Geography impacts weather.

Coastal conditions are different than inland conditions

This is due largely to differences in specific heat between water and land.

DEMONSTRATION:

Put two beakers side by side under a heat lamp.

Fill one with water, the other with sand and soil.

Measure and record the temperature in both every 60 seconds for 10 minutes.

Turn off the heat lamp. Again measure and record temperatures for 10 minutes.

QUESTIONS:

How do the two substances compare in heat absorption? Which material absorbs heat faster? Which material loses heat faster?

RAINSHADOW EFFECT

http://www.youtube.com/watch?v=GJR893xiTr0 (northern hemisphere)

http://www.youtube.com/watch?v=YWZ6yEv-gI4

http://www.youtube.com/watch?v=9OHt4wVuIwI

http://www.youtube.com/watch?v=feJ0D1DjH2M (southern hemisphere)

HOW WEATHER FORMS

Air masses form by the amount of heat and moisture they contain. When two air masses meet, the boundary between them is called a front.

• Cold air • Denser; stays near the ground• Creates a mass of high pressure

• Warm air • Rises, causing low-pressure areas• Cools as it rises

• Interactions between air masses cause weather patterns

Fronts are indicated by the red and blue lines

HURRICANES

Hurricanes form in the ocean near the equator where water receives most energy from the sun.

Water evaporates from the surface of the sea and the moist warm air then rises.

The water vapor releases latent heat as it cools and condenses into clouds. This is the source of energy which forms the hurricane.

Hurricanes lose their power when travelling over land where there is much less moisture.

At the top of the low pressure region (the eye) winds from the updraft of convection spread outwards and the coriolis force deflects the winds to make the rotational hurricane we see.

TORNADOES

Tornadoes occur over land when cold fronts collide with warm humid air moving north. The greater the temperature difference, the stronger the air currents.