Basic info on layers of atmosphere & atmospheric science Ch 17

The Composition of the Atmosphere Volcanic eruptions probably played a major role in forming the early atmosphere. – Carbon dioxide – Sulfur dioxide – Water vapor – Nitrogen – ****no oxygen Oxygen probably 1 st formed when sunlight split water vapor into hydrogen & oxygen – Amount increased significantly as early organisms (producers) carried out photosynthesis.

The Composition of the Atmosphere All other gasses: Ar, CO 2, Methane, etc.

% of nitrogen & oxygen fairly constant through atmosphere up to ~80 km (~mesopause) Amounts of some gases can vary from place to place & time to time – Ex. water vapor varies w/ location, season, time of day Highest near surface & decreases rapidly w/ altitude – Ex. carbon dioxide varies w/ seasons Lowest in summer (more p’syn, uses more CO 2 ) Highest in winter (less p’syn, uses less CO 2 ) Atmosphere also contains dust particles (rock, dirt, pollen, salt from sea spray, soot, etc.) The Composition of the Atmosphere

Recycling of Atmospheric Materials Earth’s 4 spheres are constantly recycling elements & compounds they contain. – Maintains an overall balance (in = out) through cycles – Carbon – Oxygen – Water

Carbon Cycle

The Water Cycle Exhalation

A Delicate Balance The balance of gases in the atmosphere may be disrupted by natural & human influences. – Ex. CO 2 levels have risen steadily in recent years Primarily due to human activities – Burning of fossil fuels » Coal » Gasoline » Natural gas Suspected of contributing to global warming There is also a balance in energy. – Amount of sun’s energy entering = to amount of energy reflected, absorbed, & reradiated Keeps Earth’s temperature at a level that makes life possible. – Can be disrupted » Global warming (or cooling)

Energy from the sun reaches Earth in 3 ways: – ________ is the transfer of energy through empty space. visible light, UV, & other electromagnetic (EM) waves – __________ is the transfer of energy (mostly in solids) by collisions of molecules or atoms. Air touching warm ground, feet touching cold floor – __________ is the transfer of energy by currents moving through liquids or gases (caused by density differences). Convection cells in magma, water boiling, air rising RADIATION CONDUCTION CONVECTION How Heat Energy Moves

Convection Conduction Radiation

Heat and Temperature Temperature is a measure of the average kinetic energy (or energy of motion) of the atoms or molecules in a substance. – Higher kinetic energy  higher temperature – Lower kinetic energy  lower temperature Heat is the total kinetic energy of a particular substance. – Large cup of tea  more heat than small cup at same temperature Heat flows from object of higher temperature to lower temperature

Structure of the Atmosphere The temperature of the atmosphere changes dramatically at varying altitudes (heights). – Used to divide the atmosphere into 4 layers Troposphere Stratosphere Mesosphere Thermosphere Try Smiling Many Times

Troposphere – Lowest layer, up to ~15 km above surface – Temperature decreases with altitude Earth absorbs solar radiation & transfers heat to atm – Air at surface  warmest – 78% nitrogen, 21% oxygen – 80% mass of atm (b/c of high density) – Contains most of the water vapor in atm where weather occurs – The “trouble sphere” Tropopause (~15 km) – Boundary btw troposphere & stratosphere – Altitude varies with latitude Lower at poles, higher at equator Structure of the Atmosphere

Stratosphere – 2 nd layer, kilometers above surface – Clear, dry – Temperature increases with altitude Due to presence of ozone (O 3 ) – O 3 absorbs UV radiation & releases some of it as heat Stratopause (~50 km) – Boundary btw stratosphere & mesosphere Structure of the Atmosphere

Mesosphere – 3rd layer, km above surface – Temperature decreases with altitude Due to very little ozone Mesopause (~90 km) – Boundary between mesosphere & thermosphere Structure of the Atmosphere

Thermosphere – 4 th layer, >90 km above surface – Extremely thin – Temperature increase with altitude (1000+ °C) Due to intense solar radiation – Separated into layers of different gases Heavier gases on bottom  lighter gases on top – Nitrogen, oxygen, helium (~2400 km), hydrogen (thins into space) – Ionosphere Part of thermosphere from km – Affected by solar events » Ionized (charged) particles deflected by Earth’s magnetic field to poles & interact to form auroras (colorful light) Structure of the Atmosphere

Insolation and the Atmosphere As insolation (incoming solar radiation) enters the atmosphere, the different gases absorb, reflect, or scatter particular wavelengths (colors) of light. – Red light is absorbed the least= red sunsets – Blue light is scattered by air molecules all over sky= blue sky – Ultraviolet light is absorbed by ozone= protects skin

A global heat budget model represents the overall flow of energy into & out of the atmosphere. – In balance  fairly constant temperatures – Out of balance  global warming or cooling Insolation and the Atmosphere

Heat Budget of Earth & the Atmosphere Much of the solar radiation that is absorbed by Earth’s surface is radiated back into the atmosphere as infrared radiation (heat). – Excess water vapor & carbon dioxide absorb this IR, preventing it from radiating directly back into space. Greenhouse effect – a little = good, a lot = bad

Local Temperature Variations What causes the temperature to vary from location to location? – The sun heats Earth unevenly. Due to: Time of day Latitude Time of year – The characteristics of a material also affect how much energy is absorbed, which affects temperature.

Intensity of Insolation Intensity of insolation depends on the angle at which the sun’s rays hit Earth’s surface – Highest angle (90°) = maximum intensity – Lowest angle (0°) = minimum intensity Time of day – Sun’s rays closest to vertical at noon  max. intensity Latitude – Earth’s rounded shape causes variations Equator  higher angle of insolation  greater intensity Poles  lower angle of insolation  lower intensity Time of Year – Tilt of Earth affects insolation Towards sun  max. intensity Away from the sun  min. intensity

A.Direct Rays) A. (Direct Rays) = MORE concentrated solar energy transferred to Earth. B.Diffused Rays B. (Diffused Rays) = LESS concentrated solar energy transferred to Earth. HOT COOL

INSOLATION CHANGES EastWest DAILY 1.Noon 1.Noon - more direct rays. 2. Pm/Am less direct (diffused) rays.

Summer in the Northern Hemisphere SUN direct rays Most of the sun’s direct rays hit the Northern Hemisphere Diffused rays Diffused rays hit the Southern Hemisphere EQUATOR

Diffused rays Diffused rays hit the Northern Hemisphere direct rays Most of the sun’s direct rays hit the Southern Hemisphere SUN Winter Winter in the Northern Hemisphere Sunlight & Seasons Visualization Path of Sun Latitude, Time, Season

Latitude 0˚ to 30˚ ray 45˚ to 60˚ ray 90˚ direct ray Diffused Ray Direct Light Concentrated Light Spread out.

Cloud Cover Clouds reflect more sunlight, so clear days are warmer than cloudy days. Clouds trap more heat that is reradiated from the Earth, so cloudy nights are warmer than clear nights.

Heating of Water and Land Land heats and cools faster than water. – Heat/insolation penetrates deeper into water and spreads more easily by convection – Some heat is used in evaporating water – Water has a higher specific heat than land (specific heat = the amt of heat needed to raise 1 g of a substance by 1° C) Water takes more energy to heat up than land Water loses energy more slowly than land Land has more drastic temp. differences than water. – This is why water has a moderating effect on temperature.

Different types of land also absorb (and reflect) heat differently. – Dark  absorb more energy heat up more – Light  reflect more energy (absorb less) heat up less – Rough  absorb more energy Heat up more – Smooth  reflect more energy (absorb less) Heat up less Heating of Water and Land

Temperature Maps Where are warmest temperatures in relation to: – time of year? land & water? Why??? Isotherm: – Line connecting places with the same temperature Iso = equal Therm = heat