Chapter One: The Atmosphere

Weather

Section 1: Characteristics of the Atmosphere

• Composition of the atmosphere: • made mostly of nitrogen and oxygen• 21% oxygen, 78% nitrogen• Remaining 1% made up of: argon, carbon

dioxide, water vapor, and other gases

Atmospheric Pressure and Temperature

• Atmosphere is held around Earth by gravity• Air pressure is strongest at Earth’s surface

because more air is above you• As altitude increases air pressure decreases• Air temperature changes as altitude increases• Some parts are warmer because they contain a

high % o gases that absorb solar energy• Other parts contain less of these gases and are

cooler

Layers of the Atmosphere

• Thermosphere: the edge of the atmosphere

• Mesosphere: the middle layer

• Stratosphere: the home of the ozone layer

• Troposphere: the layer in which we live

• Look at figure 3 page 6

• Troposphere:• Densest layer• Contains almost 90% of the atmosphere’s total

mass• Almost all the Earth’s carbon dioxide, water

vapor, clouds, air pollution, weather, and life forms are in the troposphere

• Stratosphere:• Air is thin, contains little moisture• Lower stratosphere= extremely cold• Temp rises as the altitude increases• Stratosphere=in ozone layer• Ozone layer= protects life on Earth by

absorbing harmful ultraviolet radiation

• Mesosphere:• Middle layer above atmosphere• Coldest layer• Temperature decreases as altitude increases• Temp can reach -93 degrees celsius

• Thermosphere:• Uppermost layer• Temp increases as altitude increases (particles

moving very fast)

Ionosphere: Home of the Auroras• Electrically charged particles=therefor called the

ionosphere• In polar regions these ions radiate energy as

shimmering lights called auroras

Section Two: Atmospheric Heating

I. Energy in the atmospherea. Earth receives energy from the sun by radiationb. Energy transferred by wavesc. Conduction: energy transfer by contact

1. thermal conduction2. thermal energy is transferred from warm to cold

areasd. Convection: energy transfer by circulation

1. cycle of warm air rising and cool air sinking causes movement of air-convection current

II. Greenhouse Effect

A. 70% of the radiation that enters the Earth’s atmosphere is absorbed by clouds and Earth’s surface-this is converted into thermal energy (energy that warms the planet)

-short wave visible light is absorbed and reradiated into the atmosphere as long-wave thermal energy

B. Atmosphere is like a blanket that traps enough energy to make Earth livable

C. Radiation Balance: for Earth to be livable-energy received from sun and amount of energy returned to space must be approximately equal-the balance of incoming energy and outgoing energy is called the radiation balance

D. Increasing levels of greenhouse gases could cause a global warming

Section 3 (p. 14)Global Winds and Local Winds

• Wind= the movement of air caused by differences in air pressure

• Air rises at the equator and sinks at the poles:-the equator receives more direct solar energy-the air at the equator is warmer/less dense-warm air rises and creates a low pressure area-the warm air flows towards the poles-the poles are colder and more dense so the air sinks-this creates an area of high pressure

Pressure belts are found every 30 degrees

• Air travels in many large circular patterns called convection cells

• Convection cells are separated by pressure belts

• Pressure belts=bands of high pressure and low pressure found at every 30 degrees latitude

The Coriolis effect

• Winds do not travel directly north or south because the Earth is rotating

• The apparent curving of winds and ocean currents due to the Earth’s rotation is called the Coriolis effect

Global Winds

• The combination of convection cells found at every 30 degrees latitude and the Coriolis effect produces patterns of air circulations called global winds

• The major global wind systems are:• Polar easterlies• Westerlies• Trade winds

Jet Streams: atmospheric conveyer belts

• Jet streams are narrow belts of strong winds that blow in the upper troposphere

Local Wind

• Local winds move short distances and can blow from any direction

• Shorelines or mountains can produce temperature differences that cause local winds

• Mountain and valley breezes are other examples of local winds caused by an area’s geography