Ch 17 - The Atmosphere

17.1 Vocab Charts (Example) WordDefinitionPicture 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 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% Nitrogen 21% Oxygen 0.93% Argon (inert gas) 0.039% Carbon Dioxide

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

–Ozone (O 3 ) is concentrated between km from surface Block harmful Ultraviolet (UV) rays –Air pollution is mainly from car exhaust

Structure 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)

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 22 nd. N.H. leans 23.5 degrees away from the sun.

Equinoxes Midway between solstices. September 22 nd or 23 rd date of Autumnal Equinox. March 21 st or 22 nd date of Spring Equinox

17.2

Heating the Atmosphere Within 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 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 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…. 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 Assignment THIS IS WORTH 25 POINTS! Page #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 Words Autumnal EquinoxConduction Convection Greenhouse Effect MesosphereOzone RadiationReflection Spring Equinox Stratosphere Summer Solstice Thermosphere Troposphere Winter Solstice