Unit 2

Seasons and Atmosphere

Day 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)

Day 2

¥  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

Day 3

The Atmosphere: Structure and Temperature

¥ 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

Composition of the Atmosphere ¥ Main Components

¥  Nitrogen – 78% ¥  Oxygen – 21%

¥ CO2 < 1% ¥ Argon < 1%

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

Pressure and Temperature Changes u  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 u  As you increase in altitude in the

Troposphere the temperature decreases.

u  Density Changes

Human Influences and Primary Pollutants

¥  Air pollution is airborne particles and gases that occur in concentrations large enough to endanger the health of organisms

¥  Primary Pollution: emitted directly from identifiable sources

¥  Secondary Pollutions: not emitted directly into air (agriculture)

Day 4

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

¥ 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

The Heating Song

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

What Happens to Solar Radiation? Reflection vs. Scattering

¥  Reflection ¥  occurs when light

bounces off an object. ¥  30 % of all radiation is

reflected back to space

¥  Scattering produces a larger number of rays that travel in many directions.

¥ Absorption:

¥  50 % of the solar energy that strikes the top of the atmosphere reaches the Earth’s surface

¥  20% is absorbed in the clouds

¥  30% is reflected back to 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

Ozone Video

Greenhouse affect

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

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

VIDEO

World Distribution and Temperatures

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

Day 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)

¥ Precipitation ¥ Condensation ¥ Evaporation

Air Mass

Water Cycle

© Precipitation is any form of water that falls from a cloud.

© When it comes to understanding atmospheric processes, water vapor is the most important gas in the atmosphere

Think about it…

¥ Have you ever been outside and the air seemed “sticky” or “wet”? Maybe it gave you “frizzy” hair…what causes this?

¥ TURN AND TALK…discuss this with your partner

Video Link: http://www.youtube.com/watch?v=7GS5jl4nLek

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

Cloud Formation

Clouds form when air is cooled to its dew point as it rises

Video: How Clouds Form

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.