Chapter 3 – Section 1Seasons & Weather

Seasons• The Earth revolves around the sun at a 23.5° angle which causes different parts

of the Earth to receive more direct rays of sunlight than other parts at different times of the day and year.• This is what causes the different seasons.

• Tropic of Cancer & Tropic of Capricorn mark the farthest points north and south of the equator that the sun’s rays shine directly overhead at noon. The day that this happens is called a solistice.• Summer Solstice: longest day (June 21/22)

• Winter Solstice: shortest day (Dec. 22/23)

• Equinox: another signal of season change; days and nights all over the world are the equal in length.• Spring Equinox: about March 21

• Autumn Equinox: about September 23

What causes weather?• Complex result of several factors:

• solar energy: amount received varies by location in relation to the sun.

• water vapor: determines if there will be precipitation (rain, sleet, snow or hail)

• cloud cover: may hold water vapor

• landforms: land heats quickly & loses heat quickly

• bodies of water: water heats slowly & loses heat slowly

• elevation: the higher above sea level, air becomes thinner & loses its ability to hold moisture

• air movement: winds move air and the solar energy and moisture it holds.

• Weather: is the condition of the atmosphere at a particular location & time.

• Climate: is the weather conditions at a particular location over a long period of time.

Types of Precipitation• Conventional: hot climates; morning sunshine heats the warm moist air;

clouds form in afternoon and rain falls.

• Orographic: mountain areas; storms drop more rain on the windward side of the mountain and create a rain shadow on the leeward side.

• Frontal: mid-latitude; cold dense air masses that push lighter warm air masses upward, causing precipitation to form.

Weather Extremes• Hurricanes/Typhoons (Asia): powerful storms that form over warm tropical

ocean water.

• Tornado: powerful funnel-shaped column of spiraling air.

• Blizzard: heavy snow storm with winds of more than 35 mph & reduced visibility.

• Drought: a long period of time without rain or very minimal rainfall.

• Floods: when water spreads over land not normally covered in water.

Tornado Alley

Chapter 3 – Section 2Climate

Factors affecting climateWind Currents

• Distribute the sun’s heat through convection: the transfer of heat in the atmosphere by upward motion of the air.

• Sunlight heats the atmosphere, air expands which creates low air pressure. Cooler dense air in a nearby high-pressure zone rushes into the low-pressure zone, causing wind.

• Coriolis effect: bending of wind currents around the globe.

Ocean Currents

• Like rivers flowing through the ocean; warm water flows from the equator toward the poles, and cold water from the poles toward the equator.

• Affect the temperature & the precipitation an area receives. Winds blowing across the ocean affect the climate of the land they cross.

Zones of Latitude

• 3 zones: • low/tropical – hot all year

• middle/temperate – have varying climates

• high/polar – cold all year

Elevation

• Distance above sea level; the higher you go the colder it gets.• Air temperature drops about 3.5% for every 1000 ft.

Mount Kilimanjaro

Topography

• Landforms affects the climate. Moisture-laden winds cool as they go up a mountain, dropping rain/snow, and then dry as they reach the other side.

Changes in climateEl Niño

• Warming of the waters of the west coast of South America; is a natural change in climate.

• Every 2-7 years, winds that blow over the Pacific Ocean slow or reverse direction, changing the ocean temperature and weather worldwide.

• Normally the winds bring rain and push warm water toward Asia & Australia – El Niñopushes it toward the Americas.• Floods & landslides in the Americas

• Droughts in Asia & Australia

• La Niña is the opposite

Global Warming

• Gradual increase in the average temperature of the Earth's atmosphere and its oceans, a change that is believed to be permanently changing the Earth's climate.

• Some warming is naturally occurring, some is man-made.

• Greenhouse Effect: Earth’s atmosphere traps in some of the sun’s heat & radiation, some of these gases radiate back into space. The increase in man-made greenhouse gases is causing the Earth to warm quicker because the gases are being trapped in the atmosphere.