The Atmosphere: Structure and...

Unit 5

Seasons and Atmosphere

Standard 1:

Revolution Motion of a body along a path

around some point in space.

Earth’s orbit is elliptical

Earth’s distance from the sun

varies

Perihelion

Earth is closest to the sun

147 million km away

Occurs on January 3rd

Aphelion

Earth is farthest from the sun

152 million km away

Occurs on July 4th

Rotation The turning or spinning of

a body on its axis

Causes day and night

Two kinds of measurement

Mean Solar Day – time interval from one noon to the next (24 hours)

Sidereal Day – time it takes for Earth to make one complete rotation (360’) with respect to a

star other than the sun (23 hours, 56 minutes, 4 seconds)

Seasons are caused by the tilting of the earth on its axis (23.5°)

When the Earth is tilted towards the Sun – warmer seasons

When the Earth is tilted away from the Sun – cooler seasons

Formation of the Universe

The Big Bang Theory

At one time, the entire universe was confined to a dense, hot, super-mass ball.,

About 13.7 billion years ago a violent explosion occurred, hurling this material in all directions.

Marks the beginning of the universe.

VIDEO LINK

Earth’s Motions

Precession

Slight movement over a period of 26,000 years

where Earth’s axis points in different directions.

Points to two stars

Polaris

Vega

Current pointing to Polaris

Has no affect on seasons.

Earth’s Motions

Nutation

Oscillatory movement of the axis of a rotating

body (wobble)

Observed during precession

Occurs about 18.6 years

Earth’s Motions

Barycenter

The point between two objects

where they balance each other.

The center of mass where two

or more celestial bodies orbit

each other.

Barycenter website with animation

The Atmosphere: Structure and

Temperature

Standard 2:

Composition of the Atmosphere

Main Components

Nitrogen – 78%

Oxygen – 21%

CO2 < 1%

Argon < 1%

Pressure and

Temperature Changes

The atmosphere rapidly

thins as you travel away from

Earth until there are too few

gas molecules to detect.

Pressure Changes As you increase in altitude, or

travel away from Earth, pressure

decreases

Temperature Changes

As you increase in altitude in the

Troposphere the temperature

decreases.

Density Changes

Layers of the Atmosphere The Troposphere - the

bottom layer Temperature decreases with an

increase in altitude.

Where weather occurs

Tropopause: boundary of the troposphere

The Stratosphere Above the troposphere

Temperature remains constant, then gradually starts to increase

Contains the ozone layer

Stratopause: boundary of the stratosphere

The Mesosphere Above the stratosphere

Temperature decreases with

height

Mesopause: boundary of the

mesosphere

The Thermosphere: Upper layer of the

atmosphere Temperature increase with

height Auroras occur here

Fades into space

Ozone

• Ozone is a form of

oxygen that

combines three

oxygen atoms into

each molecule (O3)

• Ozone filters and

absorbs harmful

UV radiation by

the sun

Heating the Atmosphere Heat: the energy

transferred from one object to another because of a direct difference in their temperature

Temperature: measure of the amount of heat

Ways Heat Can be

Transferred

Heat transfer from HOT to COLD objects

Conduction

The transfer of heat through matter by molecular activity

Transfer by touching

Convection

The transfer of heat by a mass movement or circulation within a substance

Radiation

Travels out in all directions

Solar energy reaches earth by radiation

Standard 3:

© Air pressure is the pressure

exerted by the weight of air

above

© Exerted in all directions (up,

down, and sideways)

© The air pressure pushing

down on an object exactly

balances the air pressure

pushing up on the object

© Average Air Pressure at sea

level is © 1 kg/cm2

⬜ Barometer: device

used for meaasuring air

pressure

⬜ Unit:

⬜ millibars (mb)

⬜ inches of mercury

⬜ Torricelli: invented the

mercury barometer in 1643

⬜ Wind is a result of

horizontal differences

in air pressure

⬜ Air flows from areas of

high pressure to

areas of lower

pressure.

Low Pressure Centers High Pressure Centers

Centers of Low Pressure High Pressure

AKA Cyclones Anti-cyclones

Pressure

Behavior

Pressure drops Pressure increase

Wind Behavior Winds blow

counterclockwise

Winds blow outward and

clockwise

Weather

Associated

Severe and stormy Fair and Sunny

Symbol “L” that is RED “H” that is BLUE

© The unequal heating of

earth’s surface

generates pressure

differences

© Solar radiation is the

ultimate energy source

for most wind

© Jet streams are

fast-moving rivers

of air

© Speed: 120 and

240 kilometers per

hour

© Direction: West-

to-east direction.

⬜ The atmosphere

balances itself by

acting as a giant

heat-transferring

system

⬜ Moves warm air to

the poles and cool

air towards the

equator

⬜ Coriolis Effect

⬜ Trade winds ⬜ Two belts of winds that blow

almost constantly from east to west

⬜ Westerlies ⬜ Dominate west to east motion of

the atmosphere (Jet Stream occurs here)

⬜ Polar easterlies ⬜ Winds that blow east to west

⬜ Polar front ⬜ Interaction of warm and cool

air masses produces a stormy belt

⬜Direction

⬜Labeled by the direction

from which they blow

⬜Ex: winds blowing from

the Southeast.

⬜Tool: Wind Vane

⬜ Anemometer

⬜ Measures how fast

wind is blowing

Standard 4:

The study of

weather, climate,

and atmospheric

processes

What is Meteorology?

How Does

Weather differ

from Climate? Weather is constantly changing

and it refers to the state of the atmosphere at any given time and place

Climate is based on observations of weather that have been collected over many years to help describe a place or region

Why Do

Temperatures Vary?

Factors:

Heating of land

Heating of water

Altitude

Geographic position

Cloud cover

Ocean currents

Land and Water Temperatures

Land heats and cools more rapidly

and to higher temperatures than

water

Water – heats up longer and will

retain the heat longer

World

Distribution and

Temperatures

Isotherms - lines on a weather map that connect points that have the same temperatures

⬜ Isobars

⬜ lines on a map that

connect places of

equal air pressure

⬜ A pressure gradient

⬜ The spacing of

isobars indicates

the amount of

pressure change

over a given time

⬜ Closely spaced isobars:

indicate a steep pressure

gradient and high winds.

⬜ Widely spaced isobars:

indicate a weak pressure

gradient and light winds.

Standard 5:

What is the

significance of Water

Vapor?

Water vapor - source of

all clouds and

precipitation.

The three states of matter solid, liquid, and gas

(plasma is the fourth)

amount of water vapor in air.

© Ratio of the air’s actual water-vapor content compared with the amount of water vapor air can hold at that temperature and pressure.

© Lowering air temperature causes an increase in relative humidity

© Raising air temperature causes a decrease in relative humidity

⬜ Instrument: Hygrometer ⬜ Psychrometer : a type of

hygrometer consisting of two identical thermometers mounted side by side

⬜ Dry bulb: give the present air temperature

⬜ Wet bulb: has thin wet wick tied around the end

Dew point is the temperature to which a parcel of air would need to be cooled to

reach saturation.

Clouds are classified on the basis of their form and height.

Cirrus (cirrus = curl of hair) high, white, and thin

Cumulus (cumulus = a pile) rounded individual cloud masses that have a flat base and the appearance of rising domes or towers

Stratus (stratus = a layer) best described as sheets or layers that cover much or all of the sky

Clouds form

when air is

cooled to its

dew point

Albedo the fraction of total

radiation that is reflected by any surface.

Daylight Cloud Cover

Clouds reflect solar radiation back to space

Temperatures are lower than on a clear day

Nighttime Cloud Cover

Clouds absorb radiation from land and reradiates some of it back to Earth

Temperatures are higher than on a clear night

For precipitation to form, cloud droplets must grow in volume by roughly one million times.

© The type of precipitation that reaches Earth’s surface depends on the temperature profile in the lower few km of the atmosphere

© Rain: drops of water that fall from a cloud and have a diameter of at least 0.5 mm

© Snow: light, fluffy, six-sided ice crystals

© Sleet: fall of small particles of clear to translucent ice

© Glaze: when raindrops become

supercooled as they fall through subfreezing air and turns to ice when they impact objects

© Hail: form of solid precipitation which consists of balls of irregular lumps of ice produced in cumulonimbus clouds

⬜ A cloud with its base at or very near the ground.