Unit 6 Weather and Climate

Unit Essential Question: How does the sun interact with the Earth to produce weather and

climate?

LEQ: How do weather and climate differ?

Concept #1: Weather and Climate

What is weather?

In simple terms, weather is what is taking place in the air around you at a certain place and time.

Weather takes place in the troposphere, which is the lowest layer of Earth’s atmosphere.

The atmosphere is the envelope of gases that surrounds the planet.

Layers of Earth’s Atmosphere

Important facts to remember about weather: It is powered by the sun.

It changes from day to day. The daily condition of the

atmosphere, or weather, of a particular area is based on:

Temperature (Heat)Moisture (humidity,

clouds, precipitation)Wind (moving air, air

masses, fronts) Scientist who predict the

weather are called meteorologists.

What is climate?

Climate is the name for the general conditions of temperature and precipitation for an area over a long period of time.

The climate of a region is described according to two basic factors:

temperature precipitation

Factors that affect temperature of a region’s climate: Four natural factors that affect the

temperature at a particular location: Latitude Altitude (elevation) Distance from large bodies of water

Ocean Currents

Factors that affect the temperature of a region’s climate: LatitudeWhat is latitude?

It is the measure, in degrees, of the distance north and south of the equator.

How does latitude affect climate?Areas close to the equator, or zero

degrees latitude, receive the direct rays of the sun. These direct rays provide the most radiant energy.

Areas near the equator have a warm climate. Polar regions have a cold climate.

Factors that affect the temperature of a region’s climate: LatitudeBased on Latitude, Earth’s

surface can be divided into three main temperature zones (see map on the following slide):

Tropical ZoneTemperate ZonePolar Zone

Map of world temperature zones

Earth’s temperature zones:Tropical Zone

Location: area near the equator, between 23.5 degrees north and 23.5 degrees south.

Sunlight: receives the most all year round Climate: warm

Earth’s temperature zones:Temperate Zone

Location: between the tropical and polar zones. Sunlight: strikes it more directly Climate: ranges from hot or warm in the

summer; cool or cold in the winter

Earth’s temperature zones:Polar Zone

Location: extends from 66.5 degrees north to 90 degrees north AND 66.5 degrees south and 90 degrees south.

Amount of sunlight: always strikes at a lower angle. Climate: cold

Factors that affect climate: Elevation Elevation, or altitude, is the distance above sea level.

As elevation increases, the air becomes less dense , has fewer gas molecules, and temperature decreases.

Mountain ranges, can play an important role in the amount of precipitation an area receives.

A mountain range acts as a barrier to prevailing winds. The windward side of a mountain has a wet climate.

On the leeward side, relatively dry air moves down the side of the mountain, which results in very little precipitation on the opposite side.

Factors that affect the temperature of a region’s climate: Large bodies Large bodies of waterof water

Large bodies of water, such as lakes and oceans, can affect the temperature of an area because the temperature of the water body influences the temperature of the air above it.

Temperatures of nearby lands are less extreme.

Factors that affect the temperature of a region’s climate: Ocean Currents Ocean currents help transfer heat to the atmosphere. Some warm ocean currents move water from the

equator towards the poles and warms the air above it. The warm air moves over to the nearby land.

At the same time, cold currents bring cold water from the polar zones towards the equator. As it moves, it brings cool air.

Marine climates are influenced by ocean currents. The Gulf Stream is an ocean current that carries warm

water along the eastern coast of the United States. The California Current travels toward the equator

carrying cold water along the west coast of the United States.

Map of Ocean Currents

Factors that affect the amount of Precipitation an area receives impact the climate of that region.

Prevailing Winds: directional winds that usually blow in a region such as the prevailing westerlies and the polar easterlies, which affects weather in the United States.

Presence of Mountains Seasonal Winds: sea and land breezes

over a large area that change direction with the season such as monsoons.

Prevailing winds affect the amount of precipitation

1. Weather patterns are influenced by movement of air masses.

2. Movement of air masses rely on prevailing winds, which are the directional winds that move in a particular region.

3. The temperature of the air mass determines the amount of moisture it carries. Warm air masses hold a lot of moisture while cold air masses do not.4. The direction from which the air mass comes will also determine the amount of moisture it carries. Winds blowing inland from oceans and lakes carry more water vapor than winds that blow over land.

Mountain ranges affect the amount of precipitation 1. A mountain range acts as a barrier to prevailing winds. The windward side of a mountain has a wet climate.

2. On the leeward side, dry air moves down the side of the mountain resulting in very little precipitation on the leeward side.

Seasonal winds affect the amount of precipitation

1. Monsoons happen during the summer in South and Southeast Asia when the land gradually gets warmer than the ocean.2. Sea breezes blow inland constantly bringing to the land warm, humid air.

3.As the warm air rises over land, it cools, condenses to clouds, and produces heavy rains.4. Monsoon regions receive very little rain in the winter because the land cools becoming colder than the ocean.5. Since wind moves from areas of high pressure (cold wind from the land) to areas of low pressure (warmer ocean), it carries very little moisture.

Scientists classify Earth into six broad climate regions based on temperature and precipitation received in that region:

• Tropical Rainy•Dry•Temperate Marine•Temperate Continental •Polar•Highlands

Map of Earth’s Climate Regions:

Tropical Rainy Climate Region Temperature:

Temperate wet: 18 degrees Celsius or higher

Temperate dry: always hot Precipitation:

Temperate wet: heavy rainfall year-round, about 72 cm

Temperate dry: heavy rainfall in the wet season, more than 59 in.

Usual Weather:

Temperate wet: hot and humid

Temperate dry: has distinct dry and wet seasons

Places: Temperate wet – windward side of Hawaiian Islands: Temperate dry - southern tip of Florida and Makindu, Kenya

Dry Climate Region Temperature: may be hot or cold Precipitation:

Semiarid – less than ½ inch (about 25-50 cm) per year

Arid – less than 25 cm Usual Weather:

Semiarid – little rainfall, very dry Arid – very dry, little rainfall

Places: Semiarid – Great plains in the United States Arid – Parts of California

Temperate Marine Climate Region Temperature: Averages 10 degrees Celsius or higher in the

warmest months, and between -3 degrees Celsius in the coldest months.

Precipitation: Moderate all year in marine west coast climate, about 16-68 inches per year.

Usual weather: Three sub-types of Temperate Marine Climate –

Mediterranean: warm, dry summers; rainy winters

Humid subtropical: hot summers, cool winters, hurricanes, thunderstorms.

Marine west coast: mild winters, cool summers. Places:

Mediterranean: places near the Mediterranean Sea, southern California

Humid subtropical: southeastern United States

Marine west Coast: northern California to southern Alaska

Temperate Continental Climate Region

Temperature: Average is 10 degrees Celsius or higher in the warmest month, and -3 degrees Celsius in the coldest month.

Precipitation:

Humid continental: moderate amount year-round, up to 40 inches

Subarctic: light precipitation mainly in the summer

Usual weather:

Humid continental: hot, humid summers; cold winters

Subarctic: short, cool summers; long, cold winters

Places:

Humid continental: Northern Hemisphere only, northeastern part of the United States.

Subarctic: Parts of Alaska, Canada, and Russia

Highland Climate Region

Temperature: Falls as altitude increases.

Precipitation: Increases as altitude increases.

Usual Weather:

Climate in the foothills are similar to semi-arid climate.

Higher up in the mountains would be similar to subarctic climate.

Above the tree-line would be similar to tundra climate.

Places:

Mt. Rainier in Washington State

Rocky Mountains

Polar Climate Region Temperature:

Tundra: Average is below 10 degrees Celsius in the warmest month

Ice Cap: Average is at or below zero degrees Celsius (below freezing!)

Precipitation:

Very little, mostly snow

Dry because cold air holds very little moisture.

Usual Weather:

Tundra: short, cool summers; bitterly cold winters.

Ice Cap: intense cold with dry air

Places:

Tundra: Northern Alaska, Canada, Russia

Ice Cap: Greenland, Antarctica

Outside the tropics, most regions have four distinct seasons all year long: winter, spring, summer, and fall (autumn).Seasons are not related to the distance between the Earth and the sun.

The tilt of Earth’s axis as it travels (revolves) around the sun is the cause of the seasons. The seasons change as the amount of energy (sunlight) each hemisphere receives from the sun changes.

http://www.classzone.com/books/earth_science/terc/content/visualizations/es0408/es0408page01.cfm?chapter_no=04

S6E2. Students will understand the effects of the relative positions of the earth, moon and sun. c. Relate the tilt of the earth to the distribution of sunlight throughout the year and its effect on climate.

Concept #2LEQ #1:How does heat affect changes in weather patterns?

LEQ #2: How does heat cause changes in air masses?

S6E4. Students will understand how the distribution of land and oceans affects climate and weather.

a.Demonstrate that land and water absorb and lose heat at different rates and explain the resulting effects on weather patterns. b.Relate unequal heating of land and water surfaces to form large global wind systems and weather events such as tornados and thunderstorms.c.Relate how moisture evaporating from the oceans affects the weather patterns and weather events such as hurricanes.

Today’s video review questions:

1. What causes the uneven heating of Earth’s surface?

2. What effect does the uneven heating of Earth’s surface have on the weather?

3. How does the uneven heating of Earth’s surface affect the air above it?

4. Which type of heat transfer (conduction, convection, or radiation) circulates heat in the atmosphere as well as in the oceans?

5. How does wind affect weather?

6. What is the relationship between air pressure and wind?

Temperature is the measure of motion in particles.

The faster the air particles are moving, the higher (hotter, warmer) the temperature.

The slower, the lower (colder, cooler) the temperature.Movement of heat (heat transfer) in the atmosphere causes temperatures to change, wind to blow, and precipitation to fall.

How does the uneven heating of Earth’s surface cause wind and affect weather patterns?

How is wind created and what affect does it have on weather?Warm air is less dense than

cool air so rises, and cool air tends to sink. As warm, moist air rises, less air pushes down on the area below it. This creates an area of low pressure.

As cool, dry air sinks, more air pushes down on the area below it. This creates an area of high pressure.

Air moves from an area of high pressure to an area of low pressure. This movement of air is called wind.

Important points to remember about wind and air pressure:Air always moves from an area of high pressure to an area of low pressure.

Air pressure decreases as altitude increases.

Changes in air pressure causes changes in weather.

The greater the pressure difference between two areas, the faster the air moves and the harder the wind blows.

Local Winds: Sea and Land Breezes

Global Wind Belts are caused by global convection currents and other factors. Such as the Coriolis Effect. These affects a larger area than local winds.•Doldrums•Horse Latitudes•Trade Winds•Prevailing Westerlies•Polar Easterlies•Jet Streams

Compare and Contrast Types of Winds

Local:Unequal

heating over a small area

Global:Blow from specific directions

over long distances

Jet StreamsHundreds of

kilometers wide but not deep. They blow

at speeds of 200-400km/hour. You can travel faster going from west to east if your plane gets in a

jet stream. Sea Breeze-

Cool air from water moves to take warm air’s place on land

DoldrumsWeak winds (down in the dumps)

MonsoonsUnequal heating of

land and water. Supply needed rain by crops. Occur in

South and Southeast Asia

Land Breeze-Land cools off faster than water. Cooler

air from land moves to take warm air’s place on water.

Horse LatitudesAt about 30 degrees north and south

latitude, sailors dumped the horses out of the boats.

 

  Trade WindsBlows toward the equator

 

  Prevailing WesterliesWinds towards the poles. These winds

play a large part in our water.  

 

  Polar EasterliesAway from the poles. These winds play a

large part in our weather.

   

Concept #3LEQ: How does moisture affect weather patterns?

S6E4. Students will understand how the distribution of land and oceans affects climate and weather.

a.Demonstrate that land and water absorb and lose heat at different rates and explain the resulting effects on weather patterns. b.Relate unequal heating of land and water surfaces to form large global wind systems and weather events such as tornados and thunderstorms.c.Relate how moisture evaporating from the oceans affects the weather patterns and weather events such as hurricanes.

How does moisture affect weather patterns?

Water moves from the air to land and back again through a process called the water cycle. The cycling of water in and out of the atmosphere plays an important role in determining climatic patterns.

The sun’s heat makes water evaporate into water vapor.

• The water vapor rises into the air, cools, and condenses into tiny droplets of water.

• The drops of water come together to form clouds.

The water drops become heavy and fall as rain, sleet, snow, or hail.

The rain falls or snow melts and flows to rivers, lakes, and oceans.

Precipitation

Condensation

Evaporation is when a liquid changes to a gas.

Water Cycle

PrecipitationWater that falls from the clouds

Air temperature determines the form of precipitation that falls

4 main types of Precipitation: Rain, Sleet, Snow, and Hail

Types of Precipitation

Rain

Sleet

Snow Hail

CloudsClouds form when warm, moist air

rises and cools and then condenses around particles like salt crystals, dust from soil, and smoke.

They generally form in areas of low pressure and along fronts.

Three main types are cirrus, cumulus, and stratus.

Cloud FormationCloud Formation

Cirrus CloudsCirrus Clouds Cirro- means

“curled” or “feathery”

Form highest in the sky; are made up of ice crystals; and appear as curls, tufts, or wisps.

Usually signal the end of clear weather.

Cumulus CloudsCumulus Clouds Cumulo- means “heaped”

or “piled” Cottony clouds with flat,

usually gray bases, and puffy, bright tops.

Usually signal good weather, but if atmosphere is unstable, can build into towering clouds that produce showers and thunderstorms.

Stratus CloudsStratus Clouds Strato- means “layer-like” or “sheet-

like.” Low-lying, dull-colored clouds that

form in layers or sheets. Usually bring drizzling rain or light-

falling snow.

Alto

A prefix meaning “middle range of clouds “

Used to describe clouds that lie from 6,500-18,500 ft. (1,980-5,640m).

Altocumulus

Altostratus

Nimbo

NimbostratusA rain cloud

Other Cloud Types

Cirrocumulus Cirrostratus

Stratocumulus Cumulonimbus

Humidity

The amount of water vapor present in the air.

It depends on the temperature and other factors.

Relative Humidity -is a measure of the amount of water vapor present in the air compared to the amount needed for saturation at a specific temperature.

Progress Check:

• What factors cause condensation?

• Explain in your own words how temperature, humidity, and dew points are related.

• What are the three main types of clouds?

Air Masses and Fronts

Air mass - a large body of air that has properties similar to the part of the Earth’s surface over which it develops.

Air masses are classified according to two characteristics:

1.Temperature – described as warm (tropical) or cold (polar) depends on the temperature of the Earth’s surface below it.2. Moisture – described as humid or dry, depends on whether it forms over water or land

Four major types of air masses that influence weather in North America:

1. Maritime Tropical – moist, warm air mass that form along the tropics and have low air pressure

2. Continental Tropical – dry, warm air masses that form over land that have less exposure to moisture from bodies of water.

3. Maritime Polar – moist, cold air masses that form north 50 degrees latitude and south 50 degrees latitude.

4. Continental Polar – dry, cold air masses that form over land.

Air Mass Map

What is a frontfront? www.phschool.com (fronts animations: web code cfp-4031)

Front - A boundary between two air masses of different density, moisture (humidity), or temperature.Where unlike air masses meet and collide, storms develop and other weather changes occur.The type of front that develops depends on the characteristics of the air masses and how they are moving.There are four main types of fronts:

Cold Front Warm Front Stationary Front Occluded Front

A Cold FrontCold Front occurs when a cold air mass pushes under a warm air mass, forcing warm air to rise.

A Warm FrontWarm Front occurs when a warm air mass meets and glides up over a cold air mass.

An Occluded Front Occluded Front occurs where a warm air mass is caught between two cooler air masses.

A Stationary Front Stationary Front occurs where warm and cold air masses meet, but neither one moves.

Storms: develop where two air masses meet. A storm is a violent disturbance in Earth’s

atmosphere. It is caused by changes in air pressure,

which causes rapid air movement. There are several types of severe storms:

ThunderstormsTornadoesHurricanes

Thunderstorms

A thunderstorm has rain, thunder, and lightning.

When we see big, thick, dark cumulus clouds, we might expect thunder and lightning to come.

Lightning produces light and heat  - called energy.

When the air is heated that quickly, it expands (gets bigger) and then contracts (gets smaller).  When the air expands and contracts, it creates an explosion called THUNDER.

Lightning safety – Stay indoors away from doors and windows. Do not use the telephone. Take off head sets. Turn off, unplug, and stay away from appliances, computers, power tools, & TV sets.

Hurricane A hurricane begins over

warm ocean waters and has winds that are more than 74 mph.

It has strong winds, high ocean waves, and lots of rain.

It causes floods and destroys many homes and buildings.

The hurricane season begins June 1 and ends November 30.

Stay indoors, in the center of your home, in a closet or bathroom without windows.

Tornado A tornado is a funnel-

shaped cloud that spins very fast.

It has very strong winds that can destroy many houses and buildings.

It picks up debris or buildings by its swirling winds.

Tornado safety – Stay inside away from windows, doors and outside walls. Cover your head and body to protect yourself from flying objects.