Weather and Climate

Chapter 24 -- pg. 744-787

Chapter 24.1 The Atmosphere

Key Terms: Atmosphere Air pressure Barometer Troposphere Weather Stratosphere Ozone layer Mesosphere Thermosphere Ionosphere Aurora

24.1 Key Concepts

How does the atmosphere affect conditions on Earth?

What is Earth’s atmosphere composed of?

How do pressure and density vary with altitude?

What are the characteristics of the major layers of the atmosphere?

24.1 The Atmosphere

The study of the atmosphere is called Meteorology.The study of the atmosphere is called Meteorology.

The study of meteorology also covers the study of The study of meteorology also covers the study of weather and climate.weather and climate.

Weather is the general condition of the atmosphere at a particular time and place.

Climate is the general weather conditions over a period of years.

24.1 The Atmosphere

Atmosphere: A layer of gas that surrounds Earth

The atmosphere forms a protective boundary between Earth and space and provides conditions that are suitable for life

24.1 The Atmosphere

The atmosphere holds in heat and helps regulate temperatures that are suitable for life.

The two most prevalent substances in our atmosphere are carbon dioxide and water vapor (both are waste products we exhale).

24.1 The Atmosphere

Air Pressure: the force exerted by the weight of a column of air on a surface. This weight is a result of

gravity

Air pressure changes with altitude.

Is most dense near surface and less dense as altitude rises.

As altitude increases, air pressure and density decreases

24.1 The Atmosphere

Barometer: an instrument used to measure air pressure.

As air pressure increases, mercury in the column rises.

As air pressure decreases, mercury in the column falls.

24.1 The Atmosphere

Layers of The Atmosphere:

1. Troposphere

2. Stratosphere

3. Mesosphere

4. Thermosphere

5. Ionosphere

24.1 The Atmosphere

Troposphere: lowest layer

Contains almost all atmosphere’s water vapor

Most weather takes place here

Average height is 12 km

24.1 The Atmosphere

Stratosphere: 2nd layer of atmosphere

12-50 km is height

Layer in which ozone is present Absorbs UV radiation

which is harmful to life

Layer in which planes and weather balloons travel

24.1 The Atmosphere

Mesosphere: 3rd layer of atmosphere

50-80 km in height

At top of mesosphere temps reach -90

Air moves 320 km/hr

Meteoroids that enter the atmosphere burn up here

24.1 The Atmosphere

Thermosphere: outermost layer of the atmosphere

80-? Km no boundaries

marks end of atmosphere

24.1 The Atmosphere

Ionosphere: not a distinct layer

Region of charged particles, or ions, that overlaps the lower thermosphere

Aurora: a colorful display of light in the sky

Ions become attracted to magnetic poles of Earth and start to glow. EXAMPLE: Northern Lights

24.2 The Sun and the Seasons

Key terms: Rotation Revolution Tropic zone Temperate zones Polar zones Solstice Equinox

24.2 Key Concepts

What are two ways in which Earth moves?

Who is Earth’s surface divided into zones based on latitude?

What causes the seasons?

24.2 The Sun and the Seasons

The Earth moves in two different ways

Rotation: the spinning of Earth on its axis Causes day and night 24 hours for Earth to make

one rotation

Revolution: the movement of one body around another Earth revolves around the

sun Takes 365.25 days for Earth

to make one revolution

24.2 The Sun and the Seasons

Latitude Zones: three regions within which the temperatures are generally the same

Tropic zone Temperate zone Polar zone

24.2 The Sun and the Seasons

Seasons: caused by the tilt of Earth’s axis as it moves around the sun 23.5 degree tilt

Summer Fall Winter Spring

24.2 The Sun and the Seasons

Solstices: occurs on the two days a year when the sun is directly overhead

Northern hemisphere: Summer solstice June 21st

Longest day of the year

Winter solstice December 21st Shortest day of the year

24.2 The Sun and the Seasons

Equinox: neither hemisphere is tilted towards the sun, the length of both day and night are approximately equal.

Northern Hemisphere Vernal equinox March 21st Autumnal equinox September 21st

24.3 Solar Energy and Winds

Key terms: Greenhouse effect Wind Local wind Sea breeze Land breeze Global winds Coriolis effect Monsoon Jet stream

24.3 Key Concepts

What happens to the energy the Earth receives from the sun?

How is energy transferred within the troposphere?

What causes winds?

What are some examples of local winds and global winds?

24.3 The Sun and the Seasons

Some solar energy that reaches Earth’s atmosphere is reflected back, some is absorbed by the atmosphere, and some is absorbed by Earth’s surface.

50% absorbed by surface 25% reflected by clouds, dust,

and gases 20% absorbed by clouds and

gases 5% reflected by surface

24.3 The Sun and the Seasons

Greenhouse effect: Gases in the atmosphere releases absorbed energy to the Earth’s surface

Energy is transferred in three ways:

Radiation Conduction Convection

24.3 The Sun and the Seasons

Wind: horizontal movement of air Caused by differences in air pressure

Caused by unequal heating of Earth’s surface

Naturally flows from areas of high pressure to areas of low pressure.

As air is heated it expands and becomes less dense and rises. Cool air flows to replace it thus creating wind.

24.3 The Sun and the Seasons Local Winds: The breezes that occur where land meets a large body

of water are examples of local winds. Water has a higher specific heat than land.

The sun heats and cools the land quicker than the water. The air above the land heats quicker than the air above the water

During the day: The warmer air above the water will expand and rise,

creating a low pressure area above the water. The cooler air above the land flows to replace it.

During the night: The warmer air above the water will expand and rise,

creating a low pressure area above the water. The cooler air above the land flows to replace it.

24.3 The Sun and the Seasons

Sea Breeze: The cooler air over the water flows towards land Occurs during the day time

Land Breeze: The cooler over land flows towards the water Occurs during the night time

24.3 The Sun and the Seasons

Global winds: Winds that blow over long distances from a specific direction

24.3 The Sun and the Seasons

Convection Cells: global winds move in a series of huge bands

If Earth wasn’t rotating on its axis winds would flow in straight lines.

24.3 The Sun and the Seasons

Coriolis Effect: the curving effect the Earth’s rotation has on all free-moving objects.

If the United States shoots a rocket towards the north pole it will travel exactly in a straight line. It’s the Earth’s rotation underneath the rocket that gives it the illusion of curving.

24.3 The Sun and the Seasons

Monsoon: a wind system that is characterized by seasonal reversal of direction

Extreme land and sea breeze

Summer monsoon: Brings cool temperatures

and heavy rain

Winter monsoon: Brings very hot and dry

weather

24.3 The Sun and the Seasons

Jet stream: a belt of high-speed wind in the upper troposphere

Develop at high altitudes by great differences in air pressure.

24.4 Water in the Atmosphere

Humidity: the amount of water vapor in the air.

Relative Humidity: is expressed in %. 40% humidity means

the air contains 40% water vapor.

24.4 Water in the Atmosphere

Clouds form as warm, moist air rises and water vapor condenses in the atmosphere.

Types of clouds: Stratus Cumulus Cirrus

24.4 Water in the Atmosphere

Stratus: flat layers of clouds that cover much or all of the sky. Meaning: “Spread

out”

When Nimbo or Nimbus is added to cloud’s name, it means that the cloud produces precipitation.

EXAMPLE: Nimbostratus

24.4 Water in the Atmosphere

Cumulus: puffy white clouds that look like piles of cotton balls with flat bottoms. Meaning: “Heap”

24.4 Water in the Atmosphere

Cirrus: Thin, white, wispy clouds, often with a feathery or veil-like appearance.

Often blow into an area ahead of rain-producing clouds.

24.4 Water in the Atmosphere

Forms of precipitation: Rain Snow Hail Sleet Freezing Rain

24.5 Weather Patterns

Air Mass: forms when a large body of air becomes fairly stationary over a region of Earth’s surface or as air moves over a large, uniform region like an ocean.

24.5 Weather Patterns

Fronts: a defined boundary that forms when two unlike air masses meet. 4 types of fronts:

Cold Warm Stationary Occluded

24.5 Weather Patterns

Cold front: occurs when a cold air mass overtakes a warm air mass. Cumulus or cumulonimbus clouds are often

produced. Causing severe wind and thunderstorms

24.5 Weather Patterns

Warm fronts: occurs when a warm air mass overtakes a cold air mass. Usually produces stratus or nimbostratus clouds

and a heavy steady rain.

24.5 Weather Patterns

Stationary front: two unlike air masses have formed a boundary but neither is moving.

24.5 Weather Patterns

Occluded front: occurs when a warm air mass is caught between two cold air masses

A rare front that forces the warm air mass up, cutting it off from the ground and trapping it between two cold air masses. Causes cloudy days and some precipitation.