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 1st 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, CO2, 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 CO2)• Highest in winter (less p’syn, uses less CO2)

• 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. CO2 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– 2nd layer, 15-50 kilometers above surface– Clear, dry– Temperature increases with altitude• Due to presence of ozone (O3)

– O3 absorbs UV radiation & releases some of it as heat

• Stratopause (~50 km)– Boundary btw stratosphere & mesosphere

Structure of the Atmosphere

• Mesosphere– 3rd layer, 50-90 km above surface– Temperature decreases with altitude• Due to very little ozone

• Mesopause (~90 km)– Boundary between mesosphere & thermosphere

Structure of the Atmosphere

• Thermosphere– 4th 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 90-500 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

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) = MORE concentrated solar energy transferred to Earth.

B. (Diffused Rays) = LESS concentrated solar energy transferred to Earth.

HOTCOOL

INSOLATION CHANGES

EastWest

DAILY 1. Noon - more direct rays.

2. Pm/Am less direct (diffused) rays.

Summer in the Northern Hemisphere

SUN

Most of the sun’s direct rays hit the Northern Hemisphere

Diffused rays hit the Southern Hemisphere

EQUATOR

EQUATOR

Diffused rays hit the Northern Hemisphere

Most of the sun’s direct rays hit the Southern

Hemisphere

SUN

Winter in the Northern Hemisphere

Sunlight & Seasons Visualization

Path of Sun Latitude, Time, Season

Latitude0˚ to 30˚ ray

0˚ to 30˚ ray

45˚ to 60˚ ray

45˚ to 60˚ ray

90˚ direct ray

Diffused Ray

Diffused Ray

DirectLight

Concentrated

Light Spread out.

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