Do Now: Analyze the following images. Why is one of the earth’s land surface a desert, another a

grassland, and another a forest?

Aim: What factors influence climate?

Memory Check: What is the difference between weather and

climate?

Flash Card

Fig. 7-2, p. 149

Generalized Map of the Earth’s Current Climate Zones. What is the general type of climate in NY?

Climates vary due to:

• Air circulation in lower atmosphere due to:1. Uneven heating of the earth’s surface by sun2. Rotation of the earth on its axis3. Properties of air, water, and land

• Ocean currents – Prevailing winds – Earth’s rotation – Redistribution of heat from the sun– Surface currents and deep currents

Fig. 7-3, p. 149

Global Air Circulation

Coriolis Effect• A wind deflection pattern first

identified by Gaspard-Gustave de Coriolis (1792-1843) in 1835

• Northern Hemisphere winds deflect to the right (clockwise)

• Southern Hemisphere winds deflect to the left (counterclockwise)

Convection Currents

• Solar Energy warms Earth’s surface

• Radiation heating transfers heat to the atmosphere

• Warmed gases expand, become less dense, & rise – Creates a vertical

column called a Convection Current

Surface windsWarm air currents can hold a lot of

moisture (water vapor) compared to the surrounding air

Why can warm air hold more water vapor?When the warm air rises, cooler air flows

along Earth’s surface in the warm air’s place– helps distribute heat and moisture in the

atmosphere.

Sea v. Land Breezes

Fig. 7-5, p. 150

How do you think this loop affects climates of the coastal areas around it?

Homework:

• Re-read pages 152-166

Answer critical thinking 7-8 on pg 166

• Factors Affecting Biome Distribution worksheet

Dew Point

• Occurs when warm moist air rises into the cooler atmosphere & cools to the temperature that water vapor condenses into liquid water

• Creates clouds

Fig. 7-3, p. 149

Global Air Circulation

Precipitation• When condensation continues, drops get bigger in clouds &

are too large to be held up by gravity• They fall as precipitation, which can be frozen or liquid

Convection Cells• Heat and moisture are distributed

over the earth’s surface via six giant convection cells at different latitudes. – 2 Hadley Cells– 2 Ferrel Cells– 2 Polar Cells

• The resulting uneven distribution of heat and moisture over the planet’s surface leads to the forests, grasslands, and deserts that make up the earth’s terrestrial biomes.

Winds Currents & Convection Cells Diagrams

Hadley Cells• On a local level --> accounts for land &

sea breezes• On a global scale --> cycle starts over

equator, where warm moist air evaporates & rises into the atmosphere– Accounts for tropical rain forests @

equator line due to precipitation in that region

• Then cool dry air descends 30 deg North & South of equator– Accounts for belts of deserts around Earth

at that latitude

Global Air Circulation, Climates, &

Biomes

Winds (Air Currents)

• Wind is air that is moving because of unequal heating in the atmosphere

• Usually flow from high pressure area to low

• Moves heat, moisture, soil, and pollution around the planet

Tradewinds

• Named for their ability to quickly propel trading ships across the oceans

• TW that blow between 30 deg latitude & the equator are steady, strong & travel at a speed of 11-13 mph

• Northeast Tradewinds in the Nothern Hem.– Move south and west of the equator

• Southeast Tradewinds in the Southern Hem.– Move north and west of the equator

Pic: Tradewinds across Pacific

Westerly

• Moving air mass near the equator between 30 deg and 60 deg as a result of the Coriolis Effect

• Northern hemisphere – Travels north and east

• Southern hemisphere – Travels south and east

Polar Easterlies

• Wind pattern formed from forces similar to the Coriolis Effect

• Northern Hemisphere– Lie in latitudes between 60 degrees

and the North Pole – blow south and west

• Southern Hemisphere: – Lie in latitudes between 60 degrees

and the South Pole – blow north and west

Pic: Tradewinds & Westerlies

Horse Latitudes (Subtropical Highs)

• Air movement is less predictable– Could have no wind for days

• Between latitudes of 30-35 degrees No & So of equator

• Region of subsiding dry air and high pressure resulting in very weak winds

Intertropical Convergence Zone ITCZ (Doldrums)

• Air near the equator that is relatively still because the air is constantly rising & not blowing

• Exist between 5 degrees No & So of the equator

• Tradewinds converge here producing convectional storms that produce regions that have some of the heaviest precipitation in the world

Jet Stream

• High speed currents of wind that occur in the upper troposphere

• Have a large influence on local weather patterns

Pic: Winds & Hadley Cells

Pic: Horse Latitudes, ICZ, TW, W, PE

Weather Events

• Monsoons• Rain Shadow Effect• Tropical Storms• Hurricanes• Typhoons• El Nino• Southern Oscillation• La Nina