Meteorology: Weather and Climate

Hot, Cold, and Everything in between!

Standard and Essential Question

• S6E2c. Relate the tilt of the earth to the distribution of sunlight throughout the year and its effect on climate.

How does the tilt of the earth affect the seasons and Earth’s climate?

The Seasons

1. What is the difference between rotation and revolution ?

2. What causes the earth’s seasons ?

3. What is the position of earth during each season?

4. How does Earth’s tilt cause temperature differences in the seasons ?

Rotation vs. Revolution

• The Earth ROTATES on its axis

• An axis is an imaginary line that goes through the center of the planet

• The earth is TILTED 23.5° from the vertical position of the axis

• The Earth REVOLVES around the sun

• This revolution takes approximately 365 days ( 1 year)

What causes the Earth’s Seasons ?

• The earth is divided by the equator into two halves called hemispheres ( North and South)

• The seasons are not the same on all parts of earth at the same time (winter in the Northern Hemisphere, summer in the Southern Hemisphere)

• Earth’s orbit + the way that the Earth tilts on its axis causes the seasons.• The sun’s rays strike Earth unevenly- at different angles

at different times of the year

Position of Earth

• The position where the Northern Hemisphere tilts towards the sun = summer. At the same time, its winter in the Southern Hemisphere

• The position where the Northern Hemisphere tilts away from the sun = winter. At the same time, its summer in the Southern Hemisphere

• Two points where axis is not tilted away or toward the sun. These points mark the beginning of fall and spring• Fall in Northern Hemisphere, Spring in Southern Hemisphere• Spring in Northern Hemisphere, Fall in Southern HemisphereThe seasons are always opposite in Earth’s Northern and Southern Hemispheres.

Temperature and Daylight

• The sun’s rays deliver the most energy when Direct

• When its Winter in an area, the sunlight is Less direct, meaning the area receives less Energy from the sun

• The sun’s rays deliver the most energy when Direct

• When its Summer in an area, the sunlight is More direct, meaning the area receives more Energy from the sun

Temperature and Daylight• The amount of daylight also changes with the seasons.

– Summer= more hours of daylight, so the sun heats Earth’s surface longer ( temperatures higher)

– Winter = less hours of daylight, so the sun heats Earth’s surface for a shorter amount of time ( temperatures lower)

– In the Northern Hemisphere, from Dec. 21st to June 21st the period of daylight gets longer, from June 21 to Dec. 21st, the period of daylight gets shorter

• Many parts of the earth do not have distinct seasons– Places near the equator receive direct sunlight all year long, so

temperatures remain high– The north and south poles get less direct sunlight from farther poles, so

even in summer, these places are still cold

The Atmosphere

Earth’s atmosphere is a mixture of gases that distributes heat and enables life to exist on Earth

COMPOSITION

• Earth’s ATMOSPHERE is a mixture of gases that distributes heat and enables life to exist on Earth

• Gases that make up the atmosphere :• Keep earth’s surface warm

enough to have liquid water• Protect against dangerous

radiation• Prevent Earth’s surface from

getting hit by meteors or chunks of rock from space

• Gases• Nitrogen 78%• Oxygen 21%• Other gases 1%• Water vapor <1%

• Solids• Dust, volcanic ash,

salt, dirt, smoke• Liquids

• Water

COMPOSITION

ATMOSPHERIC PRESSURE & TEMPERATURE• AIR PRESSURE is the measure of the

force with which air molecules push on a surface. • Air pressure is strongest at the

Earth’s surface because more air is above you.

• As altitude ( distance from sea level) increases, air pressure decreases

• AIR TEMPERATURE also changes as altitude increases due to the way solar energy is absorbed as it moves through the atmosphere• High % of gases that absorb solar

energy= warmer• Less gases that absorb solar

energy= cooler

Layers of the Atmosphere• TROPOSPHERE: layer in which

we live; contains almost all of the weather, carbon dioxide, water vapor, clouds, air pollution, and life-forms

• STRATOSPHERE: gases are layered and don’t mix; contains the ozone layer; protects life by absorbing harmful UV radiation

• MESOSPHERE: middle layer; the coldest layer; most meteoroids burn up here, producing meteoroid trails

• THERMOSPHERE: temperature increases; does not feel hot; outer most part of atmosphere; no definite outer limit

Atmospheric Heating

• Earth and it’s atmosphere are warmed by energy from the sun.

• We are going to discuss the three ways that this happens: radiation, conduction, and convection

Energy in the Atmosphere

Radiation: Energy Transfer by Waves• RADIATION is the

transfer of energy as electromagnetic waves

• The earth receives only about 2 BILLIONTHS of the energy radiated by the sun, but it’s enough to drive the weather cycle and make life on earth possible

• THERMAL CONDUCTION is the transfer of thermal energy through a material by DIRECT CONTACT

• Thermal energy is always transferred from warm to cold areas

• When air molecules come into DIRECT CONTACT with the warm surface of earth, thermal energy is transferred to the atmosphere.

Conduction: Energy Transfer by Contact

• CONVECTION is the transfer of thermal energy by the circulation or movement of a liquid or gas

• Most thermal energy in the atmosphere is transferred by CONVECTION

• As air is heated it becomes less dense and rise, Cool air is denser so it sinks, and as the cool air sinks it pushes the warm air up.

• This cycle of warm air rising and cool air sinking causes a circular movement of air called a CONVECTION CURRENT

Convection: Energy Transfer by Circulation

Global and Local Winds

1. Why does Air Move ?2. What is the Corliolis effect ?3. What are global winds ?4. What are local winds ? Describe the

formation of land and sea breezes

Why does Air Move ?

• The movement of air caused by differences in air pressure is called WIND

• Differences in air pressure is caused by unequal heating of the earth

• Air at the equator is warmer and less dense so it rises creating an area of LOW PRESSURE

• At the poles, the air is colder and more dense so it sinks creating areas of HIGH PRESSURE– This cold polar air then flows

towards the equator

What is the Coriolis Effect ?• The apparent curving of the

path of winds and ocean currents due to earth’s rotation is called the CORIOLIS EFFECT

• Because of the coriolis effect, in the Northern Hemisphere winds traveling north curve east ( clockwise) and winds traveling south curve west ( counterclockwise)– Flipped in the Southern

Hemisphere

What are global winds ?

• The unequal heating of Earth’s atmosphere by sunlight produces global winds.

• The combination of high-pressure polar air + low-pressure equatorial air, and the coriolis effect produce global winds.

• The angle at which sunshine strikes Earth’s surface in MAINLY responsible for the unequal heating of Earth’s surface.

Local Winds

• LOCAL WINDS generally move short distances and can blow from any direction

• They are affected by the geographical features of an area, which can produce temperature differences that cause local winds

• SEA AND LAND BREEZES ARE BOTH EXAMPLES OF THIS

Land and Sea Breezes

Sea Breeze/Land Breeze Animation

Air Masses

• Air masses are large bodies of air where temperature and moisture content are constant throughout.

• Moisture content and temperature of a mass are determined by the area over which the air mass forms.

• These areas are called source regions.

Air Masses that Affect weather in North America

Cold Air Masses– Continental polar (cP) forms

over northern Canada; brings extremely cold weather during winter; brings cool dry weather during summer

– Maritime polar (mP) forms over North Pacific Ocean; cool, very wet; rain and snow during winter; foggy during summer

– Maritime polar (mP) forms over North Atlantic Ocean; cool, cloudy and precipitation during winter; mild, cloudy during summer.

Warm Air Masses

• There are three warm air masses that affect the U.S.– Maritime tropical (mT) forms over warm water in the

Pacific ocean– (mT) forms over the Gulf of Mexico and the Atlantic

Ocean; brings hot, humid weather and hurricanes and thunderstorms during the summer; In winter, brings mild, cloudy weather

– Continental Tropical (cT) forms deserts of Mexico and Southwestern U.S.; brings clear, hot, dry weather during summer

Fronts

• The boundary between air masses of different densities and different temperatures

• There are four different fronts that you need to know : Cold, warm, occluded, and stationary

Cold Front• Cold Front – cold air moves

under warm air• Cold fronts can move

quickly and bring thunderstorms, heavy rain, or snow

• Cooler weather usually follows a cold front because the air mass behind the cold front is cooler and drier than the air mas replacing it

Warm Front• Warm Front – warm air

moves over cold air• In a warm front, the warm

air gradually replaces the cold air

• Warm fronts generally brings drizzly rain followed by clear and warm weather.

Occluded Front

• Occluded Front – warm air mass is caught between two colder air masses. Brings cool temperature and large amounts of rain and snow.

Stationary Front

• Stationary Front – cold air mass meets warm air mass; remain separate; not enough energy to move warm air above cold air mass; can bring many days of cloudy, wet weather.

Front Illustrations

• Front Illustrations

Air Pressure and Weather• Cyclones – areas in the atmosphere that has lower pressure– Air masses come together ( converge) and rise– Spiral– Causes Stormy weather

• Anticyclones – Areas that have high pressure– Air masses move apart ( diverge)– Sinking air denser then surrounding aire and pressure is

higher– Brings dry, clear weather.

Cyclone and Anticylone

Standard and EQS6E4. 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

How does an ocean affect the weather and climate of adjacent land?

Heat and Weather Patterns

1. What are the definitions of weather and climate?

2. What is a sea breeze?

3. What is a land breeze

4. What are air masses