Chapter 17

The Atmosphere: Structure and Temperature

Intro. to unequal heating…

Why is it colder toward the poles than it is near the equator?

Does this relate to climate?

First off, let’s describe…

Weather Defined

Weather is …… The state of the atmosphere at any

time and place is. Continually changing. The combination of Earth’s motions

and energy from the sun produce a variety of weather.

Climate Defined

Climate is….based on observations of weather that

have been collected over many years. Climate helps describe a place or

region. Often refers to average temperature

and rainfall amounts at given times of the year.

Composition of the Atmosphere Earth’s early atmosphere was much

different. Volcanic activity provided most of

the original gases. Oxygen didn’t start to accumulate

about 2.6 billion years ago. Photosynthetic organisms began

Interactive Atmosphere

The atmosphere continuously exchanges materials with the ocean and life on Earth.

Major Components

Air is a…..

A. compoundB. Mixture

MIXTURE

Composition of Atmosphere Air is mostly gas with a few variable

components. Gases include: Nitrogen – 78% Oxygen – 22% The remaining 1% includes: Argon - .93% CO2 - .039% - Although only a small amount,

this gas absorbs energy given off by Earth. This is very important in heating the

atmosphere.

Variable Components

These components vary from time to time and from place to place…….

Variable components include: Water vapor Dust Ozone

Variable Components

These components can have significant effects on weather and climate.

The water vapor varies from almost none to about 4% by volume.

Water Vapor

Why is this small amount so significant?

Water vapor is the source of all clouds and precipitation.

It also absorbs heat given off by the Earth and absorbs some solar energy.

Movement of Atmosphere

Movements of the atmosphere allow a large quantity of solid and liquid particles to be suspended within it.

Microscopic dust can stay in the atmosphere for many years.

Example: Volcanic dust may stay in the atmosphere for 100 years.

Other substances include: Sea salts Fine soil blown into the atmosphere Smoke Soot Pollen Microorganisms

Ozone Ozone – is a form of oxygen that

combines three oxygen atoms (O3) into each molecule.

REMEMBER: This is not the form of oxygen we breathe.

Ozone

Ozone is not evenly distributed. It is concentrated about 10-50 km above the Earth’s surface.

At this altitude 02 is split into single atoms when they absorb ultraviolet radiation.

Ozone forms from the collision of single oxygen atoms (0) with a molecule of 02.

0 + 02 = 03

UV rays are very, very harmful Ozone is crucial to life on Earth.   Imagine what Earth would like if all

the sun’s ultra-violet radiation was not filtered out.

The Changing Hole in the Ozone Layer

Human Influence Air pollutants are airborne particles and

gases that occur in large enough quantities to endanger the health of organisms.

Primary pollutants include: CO – 49.1% Nitrogen oxides – 14.8% Volatile organics – 13.6% Sulfur oxides – 16.4% Particulates – 6%

Air Pollution

Sources include: transportation fuel combustion industrial processes solid waste disposal

Secondary Pollutants Secondary pollutants form in the

atmosphere when reactions occur between primary pollutants.

Example: After sulfur dioxide enters the atmosphere it combines with oxygen to form sulfur trioxide. Sulfur trioxide combines with water to form H2SO4 or sulfuric acid.

Smog

Example: Some reactions are triggered by sunlight and are called photochemical reactions.

When nitrogen oxides absorb solar energy a chain of complex reactions begins.

If certain volatile organic compounds are present, secondary products form that are reactive, irritating, and toxic….. smog

Height and Structure of the Atmosphere

The atmosphere thins as you travel away from Earth until there are too few gas molecules to measure.

Pressure Changes Atmospheric pressure is simply the weight

of the atmosphere. At sea level the average air pressure is

just over 1000 millibars (14.7 lbs/in2). One half of the atmosphere lies below the

altitude of 5.6 kilometers. Above 100 kilometers, only .00003% of

the gases exist. Therefore, as you gain altitude there is

less air pressure.

Temperature Changes Most of the time

temperature decreases with altitude.

The atmosphere can be divided into four vertical layers

Earth – Sun Relationships How much of the sun’s energy

actually reaches the Earth? (1/2,000,000,000) One – two billionth. This energy is not evenly distributed,

it varies with latitude, time of day, and season of the year.

Depends on the angle the sun’s rays hit the earth.

Uneven Heating

This uneven heating causes the winds and drives the ocean currents.

Think of how ocean currents try to even the distribution of heat around the Earth (Oceanography again?)

Earth’s Motions The Earth rotates once is about 24

hours. It orbits the sun at about 113,000

km/hr in an elliptical orbit.

Earth’s Orientation Seasonal changes occur because the Earth is

tilted 23.50. The constant movement of the Earth causes

solar noon to vary up to 470.Example: New York City has a maximum solar

angle 0f 73.50. As you can see the sun is never actually straight

(900) overhead. This occurs on June 21st. Six months later solar noon reaches a minimum

of 26.50.

Solstices and Equinoxes

Length of Day The farther north you are from the

equator on the summer solstice, the longer the period of daylight. When your reach the Arctic Circle, at 66.5 degrees N. latitude the length of daylight is 24 hours.

Arctic Summer

Heating the Atmosphere The concept of heat is often

misunderstood…. Heat is the energy transferred from one

object to another because of a difference in their temperatures.

Temperature is the measure of the average kinetic energy of the individual atoms or molecules in a substance 

Energy Transfer

When energy is transferred to the gas atoms and molecules in air, those particles move faster and air temperature rises.

When air transfers energy to a cooler object, its particles move slower, and air temperature drops.

Energy Transfers as Heat Three mechanisms of energy transfer as

heat are: Conduction – is the transfer of heat

through matter by molecular activity. Good conductors include metals. Air is a

poor conductor of heat. Conduction only occurs between the air

and the Earth’s surface that is direct contact with the air.

For the atmosphere, conduction is the least important mechanism of heat transfer.

Convection

Convection – is the transfer of heat by mass movement or circulation with in a substance.

Convection takes place in fluids like the ocean and air where the atoms and molecules are free to move about.

Convection also occurs in solids that behave like fluids like materials in the mantle.

Electromagnetic Radiation All forms of light that originates at the

sun form the electromagnetic spectrum.

All forms and wavelengths of light travel at a speed of 300,000 km/sec

LIGHT SPEED

Radiation

Radiation – travels out in all directions for its source.

Radiant energy can travel through the vacuum of space.  

Solar energy reaches Earth by? radiation

Four Laws of Radiation

Four laws the govern radiation:1. All objects, at any temperature,

emit radiant energy. The sun, the Earth, the poles2. Hotter objects radiate more total

energy per unit area than colder objects do.

Laws Cont.

3. The hottest radiating bodies produce the shortest wavelengths of maximum radiation.

The sun emits energy with the visible light range while Earth emits light in the infrared range.

Laws Cont.

4. Objects that are good absorbers of radiation are good emitters as well.

The atmosphere does not absorb certain wavelengths or radiation, but is a good absorber of other wavelengths.

Write a small description that explains how this water is being heated… You must include the terms you think heat the water like radiation, conduction, and convectionSend via email or bring in a hard copy.

Now that you are an expert on heat transfer…………….

What Happens To Solar Radiation? When radiation strikes an object,

there are usually three different results:

1. Some energy is absorbed by the object.

When absorption occurs radiant energy is converted to heat energy.

Pass through or reflect…

2. Substances such as water and air are transparent to certain wavelengths of radiation.

Energy that is transmitted does not contribute energy to the object.

3. Some radiation may bounce off the object without being absorbed or transmitted.

Reflection and Scattering Reflection occurs when light

bounces off an object. The reflected radiation has the same

intensity as the incident radiation. Scattering produces a large number

of weaker rays that travel in different directions.

Albedo About 30% of the radiant energy

that reaches Earth’s atmosphere is reflected back into space.

This energy is lost and does not heat the Earth or its atmosphere.

Scattering

Some dust particles and gas molecules scatter some incoming radiation in all directions.

This is how some light reaches beneath a shade tree.

Scattering also accounts for the brightness and even the color of the atmosphere.

Why is the sky blue? As light moves through the atmosphere, most of the

longer wavelengths pass straight through. Little of the red, orange and yellow light is affected by the air.

Much of the shorter wavelength light is absorbed by the gas molecules. The absorbed blue light is then radiated in different directions. It gets scattered all around the sky. Whichever direction you look, some of this scattered blue light reaches you. Since you see the blue light from everywhere overhead, the sky looks blue.

Absorption

The atmosphere efficiently absorbs the longer wavelengths emitted by the Earth.

Water vapor and carbon dioxide are major absorbing gases.  

When a gas molecule absorbs light waves, this energy is transformed into molecular motion that can be detected as a rise in temperature.

Absorption About 50% of the energy that strikes the

top of the atmosphere reaches the Earth’s surface and is absorbed.

Most of this energy is reradiated skyward. Since the Earth is cooler than the sun it

emits longer wave radiation in the infrared range.

Greeenhouse Effect

This energy can be: Radiated away Reabsorbed by other gas molecules Absorbed by the EarthThis phenomenon has been termed

the greenhouse effect.

                                                                                    

              

Temperature Controls

Why Temperature Varies includes: 1. Latitude 2. Variation in the angle of sunlight 3. Heating land and water 4. Altitude 5. Geographic position 6. Cloud cover 7. Ocean currents

Land and Water Different land surfaces absorb varying

amounts of incoming solar radiation. The largest contrast is between land and

water. Land heats more rapidly to higher

temperatures than water. Land also cools more rapidly and to lower

temperatures that water.

Temperature Variations Therefore, temperature variations are

considerably greater over land than water.

More land in the north, more water in the south 61% of the Northern hemisphere is

covered by water and 39 % land. 81% of the Southern hemisphere is

covered by water and 29% land. Which hemisphere has smaller annual

temperature variations?The Southern hemisphere

Geographic position Compare the east coast of the U.S.

with the west coast of England. England has cooler summers and

milder winters.

Coastal vs. Interior

Seattle and Spokane, Washington – temperature variation occurs because of a mountain range.

Seattle has a more marine influence. Spokane is separated from the

ocean by the Cascade Range and has a more continental influence and larger temperature variation.

Altitude Temperatures tend to drop with

altitude.

Cloud Cover and Albedo Albedo is the fraction of total

radiation that is reflected by any surface.

Many clouds have a high Albedo, and therefore reflect a significant portion of the sunlight that strikes them back in space.

Cloud cover

The extent of cloud cover influences temperatures in the lower atmosphere.

At night clouds have the opposite effect. Clouds act like a blanket by absorbing outgoing radiation emitted by the Earth and reradiating a portion of it back to the surface.

Cloudy nighttime temperatures don’t drop and much as clear night temperatures.

Cloud Cover

The effect of cloud cover is to reduce the daily temperature range by lowering the daytime maximum and raising the nighttime minimum.

World Distribution of Temperatures Isotherms - are lines on a weather

map that connect points that have the same temperature.

3234

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34 33 32 3332

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44414245

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5556

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5157

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60

656664

6867

65

7376727473

World Records

Highest temperature ever recorded on Earth was 590C.

It occurred on September 13, 1922, at Aziza, Libya in North Africa’s Sahara Desert.

Lowest Temp. Ever

Lowest temperature ever recorded on Earth was –890C.

It occurred on August 24, 1960, at Antarctica.