Ch 17 - The Ch 17 - The AtmosphereAtmosphere

17.1 Vocab Charts (Example)

Word Definition Picture

Weather the state of the atmosphere at a given time and

place

Weather = the state of the atmosphere at a given time and place (constantly changing)

- controlled by Earth’s motions & energy from the sun

Climate = the given weather conditions of an area over many years

- covers average rainfall, avg. temperature, avg. humidity, avg. wind direction, avg. air pressure etc…

Composition of the AtmosphereComposition of the Atmosphere

• Earth’s early atmosphere thought to be created by large volcanic eruptions of gas

• Oxygen was not present in the atmosphere until ~2.5 billion years ago

• Current atmosphere constantly exchanging gases with oceans and life on Earth

• Current composition of atmosphere:78% Nitrogen21% Oxygen0.93% Argon (inert gas)0.039% Carbon Dioxide

Composition cont…Composition cont…

Also present in atmosphere = water vapor, dust, ozone, and pollution–Water vapor makes up clouds &

precipitation

– Ozone (O3) is concentrated between 10 -50 km from surface

• Block harmful Ultraviolet (UV) rays

– Air pollution is mainly from car exhaust

Structure of AtmosphereStructure of Atmosphere

- There is no distinct boundary between the atmosphere and outer space, but it does thin as you increase in altitude

The atmosphere is divided into 4 layers based on temperature:

1. Troposphere = temperature decreases as you increase altitude

- Extends from surface to ~12 km- All weather occurs here

2. Stratosphere = slight increase in temperature

- Extends from 12km to ~50 km

- Contains the Ozone Layer (absorbs UV to increase temperature)

http://en.wikipedia.org/wiki/File:Atmosphere_composition_diagram.jpg

3. Mesosphere = temperatures decrease with altitude

- No definite upper limit - Temperatures near

-90ºC

4. Thermosphere = temperatures increase due to absorption of high energy solar radiation

- No definite upper limit

Troposphere, Stratosphere

Earth’s Orientation

Seasonal changes occur because Earth’s position relative to the sun continually changes as it travels along its orbit.

Solstices and Equinoxes

Solstices

• Summer Solstice: First official day of summer. Northern Hemisphere leaning 23.5 degrees towards sun.

• Winter Solstice: (opposite side of the orbit) December 21 or 22nd. N.H. leans 23.5 degrees away from the sun.

Equinoxes

• Midway between solstices.

• September 22nd or 23rd date of Autumnal Equinox.

• March 21st or 22nd date of Spring Equinox

17.2

Heating the AtmosphereHeating the AtmosphereWithin the atmosphere heat is transferred 3

ways:

1. Conduction = transfer of heat through direct contact of molecules

- heat flows from the hotter object into the colder object

2. Convection = transfer of heat by mass movement or circulation within a substance

- heat from below (ground) conducts heat near the base of the atmosphere, the air rises & expands causing cooler air to sink = circulating air patterns within the atmosphere

Convection

3. Radiation = heat is radiated (travels by waves) from the sun and hits the atmosphere

- some radiated energy is absorbed and some is reflected (bounced) back into space

~30% is reflected back into space

~50% is absorbed by land & sea

~20% is absorbed by clouds & atmosphere

Radiation

Greenhouse EffectGreenhouse Effect• Earth’s atmosphere naturally

absorbs heat from the sun because of water vapor & carbon dioxide composition

• The atmosphere also traps heat (infrared waves) near the Earth’s surface

• Without this natural greenhouse effect, Earth’s temperature would be much colder (uninhabitable for humans)

• Increased levels of carbon dioxide (mainly from car exhaust) increases the atmosphere’s ability to trap heat = Earth’s temperature is getting warmer

Global Warming • Increased levels of

CO2 (mainly from car exhaust) which increases the atmospheres ability to trap heat.

• Earths’ Temperature is getting WARMER

17.3

Why do temperatures vary Why do temperatures vary so much on Earth?so much on Earth?

5 Reasons:

1. Latitude (distance from the equator)– Differences in amount of solar radiation

received– Variations in the angle of sun’s rays– Length of daylight

2. Heating of land & water- Land heats more rapidly and to higher temperatures than water- Land also cools more rapidly and to lower temperatures than water

- Cities near water have a smaller daily temperature change compared to cities more inland

3. Altitude

- The higher the altitude, the colder the temperatures

Continued….Continued….4. Geographic Position (related to

prevailing wind direction)- A town on the ocean, with the wind

blowing in from the ocean, will, experience moderate temperatures (cool summers & mild winters) EX: S. California

- A town near mountains and the ocean will experience moderate temperatures & increased rain because mts act like a barrier to wind & rain

EX: Seattle, Washington

5. Cloud Cover

- Clouds reflect a significant amount of solar radiation

- Cities with lots of cloud cover will have significantly lower temperatures than a location with sunny weather

- Clouds at night keep heat trapped at surface, clear nights allow heat to escape into space and make chilly nights

Albedo- fraction of total radiation that is reflected by any surface

(Clouds have high albedo bc large portion of sunlight is reflected back to spaces.

Word Distribution of Temperature

• Map used to study global temperature patterns and effects of factors on temperature such as latitude, distribution of land, and water and ocean currents.

• Isotherms- are lines that connect points that have same temperature

Ch 17 Final AssignmentTHIS IS WORTH 25 POINTS!

Page 499 - 500

#1, 2, 4, 6, 8 = write out both question and answer

#11, 12, 13, 17, 18, 27 = write out only answers in complete sentences

Vocabulary WordsAutumnal Equinox ConductionConvection Greenhouse Effect

Mesosphere Ozone

Radiation Reflection Spring Equinox StratosphereSummer Solstice ThermosphereTroposphere Winter Solstice