Chapter 3Climates of the Earth

Earth-Sun Relationship• Climate and Weather– Weather- short time period– Climate- long time period

• Earth’s Tilt and Rotation– Tilt is one reason for the variations in sunlight– Because of the tilt of the axis not all places on the planet receive

the same about of direct sunlight– Angle of the tilt affects the temperature. Measured in degrees

on a set scale. – Also depends on whether or not the side of the planet is facing

the sun. – Rotates on its axis making one complete rotation every 24 hours.

Earth’s Revolution

• Also traveling in an orbit around the sun. To complete one trip around the sun it takes a few hours over 365 days

• Revolution and tilt changes the angle and amount of sunlight. Follow a regular pattern which are our seasons.

• Seasons are reversed in northern and southern hemispheres. • Equinox- March 21- sun’s rays fall directly on equator making day and

night equal.

Earth’s Revolution

• Tropic of Cancer and Capricorn• Sun’s rays directly hit the Tropic of Cancer at 23 ½ °N. It is the most northern

point to receive direct sunlight. June 21- Northern Hemisphere- longest day of sunlight. Solstice- beginning of summer

• September 22- Equinox. Sun is directly over the Equator again. Start of Fall in the North.

• Tropic of Capricorn- 23 ½ °S. southern most area to receive direct sunlight. December 22. Winter Solstice. Shortest day and the start of winter in Northern Hemisphere.

• The Poles• For six months out of the year, one pole is titled directly at the sun and receives

constant sunlight while the other is in complete darkness. • North- March 20 to September 23rd. • South- September 23- March 20th

Greenhouse Effect

• Only part of sun’s radition passes through atmosphere. Reflects some back into space

• Atmosphere acts like the glass in a greenhouse. It traps sun’s energy for growing plants even in the winter

• Without this it would be too cold to live on Earth. Atmosphere provides the right amount insulation to promote life here on earth.

• 50% of radiation that makes it through is converted to infrared radition or heat. Clouds and greenhouse gases absorb the heat reflected by earth and raditate back again so a balance occurs.

• Global warming- rise in atmospheric CO2 levels causes a rise in temperatures.

• Things like burning fossil fuels release more cabron dioxide which traps more heat. Make weather patterns more extreme. Not everyone agrees with the theory.

Factors Affecting Climate

• Latitude-• Within each of the latitude zones the climate follows a general pattern• Low latitudes:

• Between 30° S and 30 ° N. • Includes the Tropic of Capricorn, the Equator and the Tropic of Cancer• Part of it receive direct sunlight all year round• Warm to hot climates

• High latitudes:• 60 ° N and 90 ° N and 60 ° S and 90 ° S. Polar areas. • Continuous but indirect sunlight when tilted towards the sun. • Arctic Circle- 66 1/2 ° N and Antarctic Circle- 66 1/2 ° S

• Mid-latitudes:• Variable weather found here. Between 30 ° N and 60 ° S and 30 ° S and 60 ° S. • Generally have a temperate climate- ranges from fairly cold to fairly hot• Warm/hot and cold/cold air masses affect weather throughout the year

Factors Affecting Climate

• Elevation• Relationship between the elevation of a place and its temperature. This

happens no matter the latitude• Atmosphere thins as altitude increases. Thinner air is less dense and keeps less

heat. • As elevation increases the temperature drops 3.5 ° F for each 1,000 feet. • Ecuador- city of Quito is nearly on the Equator. Lies in the Andes at an elevation

of more than 9,000 feet. Average temps are 32 ° F• Sunlight is also brighter in these places because there is less atmosphere to

filter the rays. Sun does not always equal heat in these places.

Wind and Ocean Currents

• Air moving across surface is called wind. Happens when sunlight heats surface unevenly. Rising warm air creates areas of low pressure and sinking cool air causes areas of high pressure. Cool air replaces the warm air. Winds distribute sun’s energy around the planet.

• Wind Patterns• Tropical air moves towards the Poles and the polar air moving towards the

Equator. • Prevailing Winds- global winds. Determined by latitude and is affeced by earth’s

movement. • Because Earth rotates the winds in the Northern Hemisphere rotate clockwise

and counterclockwise in the Southern Hemisphere. • Coriolis effect causes the winds to blow diagonally rather than along structured

lines.

Wind and Ocean Currents

• Horse Latitudes• At Equator winds either go north or south. There is a windless band called the doldrums. • Two other bands of calm air encircle the globe. Just north of Tropic of Cancer and just

south of Tropic of Capricorn. • Called horse latitudes because during the times of actual sailing they feared getting

caught in these and threw livestock overboard to catch even the slightest breeze.

• Ocean Currents• Cold and warm streams of water, known as currents, also move in patterns. • Caused by some of the same factors- rotation, changes in air pressure, differences in

water temperature. • Coriolis effect is also present in ocean currents. • Warm water currents start in the polar areas and then warm as they move closer to the

Equator. Opposite happens for the cold currents. • Ocean currents affect the climates along the coastlines. North Atlantic Current flows

along western Europe giving it a mild climate despite the high latitude.

Wind and Ocean Currents

• Weather and Water Cycle• Wind and water work together to affect weather. • Warmer temperatures create condensation which creates percipitation which

causes cooling temperatures.

• El Niño• Climate is all affected by events that alter weather patterns. • Most famous is El Niño. Periodic change in pattern of ocean currents, water

temperatures and weather in the mid-Pacific regions. • Not every year but has increased over the past several years. • Normally low atmospheric pressure over western Pacific rises and the normally high

pressure over the eastern Pacific drops. Causes trade winds to slow or reverse direction. Reverses equatorial ocean currents

• Influences climates around the world. Precipitation increases, warms winters, increases chances for floods. Droughts and massive forest fires.

Landforms and Climate

• Absence or presence of landforms can change climates even when they are in the same latitude.

• Large bodies of water are slower to heat and to cool than land• Water temperatures are more uniform and constant than land

temperatures. • Coastal lands most affected. Less changeable weather than inland

areas• Mountain ranges affect precipiation and climate. Winds push

upwards when they meet mountains. Rising air cools and releases moisture on the windward side. After this winds become drier and warmer as they come down the leeward side

• Produces rain shadow- hot dry air with little precipiation. Makes dry areas, even deserts on the leeward side of mountains.

Climate Regions

• Climate regions are broken down into smaller regions. • Each region has its own soils and natural vegetation• Tropic Climates

• In or near low latitudes. Most widespread climates are tropical wet and tropical dry.

• Tropical wet- average temperature of 80°F. warm humid air is saturated with moisture. Rains almost every day. Yearly rainfall is about 80 inches. Very rich soil and lots of animal life. Rain forest vegetation grows in thick layers. Canopy. Amazon River basin. Parts of South America, the Caribbean, Asia and Africa

• Tropical dry- dry winters and wet summers. High year round temperatures. Few trees exist. Savannas. Found in Africa, Central and South America, Asia and Australia

Climate Regions

• Dry Climates• Occurs in low and mid latitudes. • Deserts- dry areas with almost no vegetation. Yearly does not exceed 10 inches.

Temperatures vary widely. Occur in just under 1/3rd of Earth’s total land area. Sahara extends over almost the entire northern third of Africa. Natural vegetation is scrub and cactus. Some times have oasis.

• Steppe- border the deserts. Dry, largely treeless. Rainfall average 10-20 inches a year. Largest steppe stretches across eastern Europe and western and central Asia. North and South America, Africa and Australia.

Climate Regions

• Mid-latitude Climates• Four temperate climates. Variable weather patterns and seasonal changes.

Variety of natural vegetation. • Marine West Coast- 30°N and 60°N and 30°S and 60°S. Pacific coast of North

America. Ocean winds bring cool summers and damp cool winters. Has both deciduous and coniferous trees.

• Mediterranean- land surrounding Mediterranean Sea. Mild rainy winters and hot sunny summers. Tickets of woody bushes and short trees. Any coastal mid-latitude areas with similar climate and vegetation. Southwest Australia.

• Humid Subtropical- southeastern U.S. short, mild winters and year round rain. Wind patterns and high pressure keep humidity high. Prairies and forests of evergreen and deciduous trees.

• Humid Continental- landforms influence climate more than other factors. Inland areas. Further north you go the longer and more severe the winters and shorter and cooler the summers are. Vegetation similar to marine west coast with more deciduous trees.

Climate Regions

• High-Latitude Climates• Freezing temperatures throughout the year. Vegetation is limited• Subarctic climate- South of Arctic Circle. Bitterly cold winters, summers short

and cold. Widest temperature ranges. 120°f. permafrost. • Tundra- closer to the Poles. Bitter cold and darkness for several months. Long

summer days with limited warming effects. Little vegeations. Snow and ice, some times 2 miles thick, constantly cover the ice cap areas.

• Highland Climates• These areas have similar characteristics of the high latitude climates because of

elevation. • Higher elevation, the cooler temperatures. • Vegetation also varies. Mixed forests at the bottom of the mountains. Higher up

are meadows with small trees, shrubs, and wildflowers.

Climate Changes

• Climates change gradually over time • Ice ages affect climate. • Human interaction with the environnent also affects climate. • Fossil fuels, acid rain, smog, river diversions.