Chapter Three, Section One

Seasons and Weather

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What causes the changing seasons?

• Earth revolves around sun

• Earth’s tilt (23.5 degree angle) allows a more direct line to sun’s rays

• As Earth continues to move, location becomes either further or closer to direct line with sun

• Amount of sun affects atmospheric pressure, temperature, rainfall, hence we have our distinct seasons

Where are the tropics?• Tropic of Cancer - northern tropic• Tropic of Capricorn - southern tropic• Solstice: the day on which sun’s rays shine

directly overhead at noon at either Tropic• Summer solstice--longest day of year• Winter solstice--shortest day of year

(depending on where you live)• Equinox: biannual times when days and night

all over the world are equal in length– Equinoxes mark the beginning of spring and

autumn

What is the difference between weather and climate?

• Weather: condition of atmosphere at a particular location and time

• Climate: term for weather conditions at a particular location over a long period of time

What causes weather?• Many conditions affect weather:

– Amount of solar energy– Water vapor: cause precipitation– Cloud cover: hold water vapor– Landforms and bodies of water– Elevation: as increase, air is thinner, less able to

hold moisture– Air movement: winds

Is all Precipitation the same?• NO, DUH!!!!• 1) Convectional: characteristic to hot climates;

morning sunshine heats warm moist air; clouds form in afternoon, rain falls

• 2) Orographic: characteristic of mountain areas; storms drop rain on windward side of mountain, creates rain shadow on leeward (opposite) side; the rain shadow effect

• 3) Frontal: characteristic of mid-latitude frontal storms; cold dense air push lighter warmer air upward, causing precipitation to form

Weather Extremes

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Hurricanes• Storms that form over warm, tropical ocean waters• Also called: in Asia - typhoons; in Australia - tropical

cyclones, willy-willies; in the Philippines - baguios; in Mexico - chubascos

• Places where ocean water temperature is 80 degrees or higher, huge amounts of moisture and heat energy is picked up.

• Water-laden (or filled) winds flow into core, or “eye”• The “eye” can be 10 to 20 miles across and has clear, calm

skies• Winds around eye can be as strong as 200 miles per hour• Clouds and winds can stretch over large areas, up to 500

miles• Low-lying coastal areas are vulnerable

Tornadoes• Form quickly, without warning

• Also known as a twister, powerful funnel-shaped column of spiraling air

• Cold, dry air collides with warm, moist air

• Winds swirl counter-clockwise around low-pressure center

• Winds may read 300 mph

• Usually flat plain areas are vulnerable

• Tornado Alley: midwest US

Blizzards• Common in Senegal, chuckle, chuckle

• Heavy snowstorm with high winds (35 mph)

• Some parts of US are frequently hit with snowstorms - snowbelts around Great Lakes

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Droughts

• Long period of time without rain or with very minimal rainfall

• 1930s in US --dust bowl

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Floods• Water spreads over land not normally

covered

• Can be from melting snow, rainwater filling small streams, overflowing rivers

Chapter 3, Section 1

• What did we learn?

• Now: video time

• Homework: 1) blog 2) pre-reading for Tuesday: page 54 - 58 3) worksheets: page 8 and 9