The Basics of Geography

Part 5

Weather and Climate

SeasonsAs the earth revolves around the

sun, its 23 ½ degree angle causes much of the world to have different seasons.

This tilt causes different parts of earth to receive more direct rays at different times of the year.

The Solstices Twice a year, we have what is

known as a SOLSTICE.These days mark the furthest north

or south from the equator that the sun’s rays shine directly overhead.

The solstices mark the first days of summer and winter.

The line of latitude at 23½° N where this happens is called the TROPIC OF CANCER.

The line of latitude at 23½° S where this happens is called the TROPIC OF CAPRICORN.

The sun’s rays are directly over the Tropic of Cancer. This would mark the beginning of

summer in the Northern Hemisphere.

The sun’s rays are directly over the Tropic of Capricorn. This would mark the beginning of

summer in the Southern Hemisphere.

The EquinoxesTwice a year we go through an

EQUINOX.On these two days, the sun shines

directly over the equator, and the days and nights are equal all over the world.

The equinoxes mark the beginnings of spring and fall.

The sun’s rays are directly over the equator twice a year.

• It is interesting to note that the seasons in the southern hemisphere are exactly opposite of

what we experience here in the northern hemisphere.

The Difference Between Weather and Climate

WEATHER: The condition of the atmosphere at a particular location and time.

CLIMATE: Weather conditions at a particular location over a long period of time.

Weather Extremes

As air masses warm and cool and move across earth’s surface,

sometimes they clash and cause storms. At times, these storms can be

severe and cause major property damage and loss of life. Hurricanes,

tornadoes, blizzards, and droughts are all examples of weather extremes.

Storms that form over warm, tropical ocean waters are called HURRICANES, or typhoons in Asia. They are also sometimes called cyclones.

Air flowing over warm water picks up moisture and heat energy.

The center or EYE of the storm is calm, while elsewhere, winds may blow up to 200 m.p.h.

The clouds and wind may stretch out over an area covering hundreds of miles.

When they hit land, tremendous damage may occur.

Howling winds may uproot trees and tear roofs off of buildings.

Storm surges may wash away shorelines and cause flooding.

Heavy rains may also cause flooding. People living in low-lying coastal areas

are at great risk.

Gulfport, Mississippi after Hurricane Katrina 2005

New Orleans—August 2005

Hurricanes may take days to develop, while TORNADOES, or funnel-shaped columns of spiraling air form quickly.

Tornadoes are born in thunderstorms when counter-clockwise winds swirl around a low-pressure center.

These winds may reach 300 m.p.h. and cause horrendous damage.

On average, they are only about 300 feet wide and travel a mile or so for a few minutes. Some may be larger.

Look at the swath of

damage that was cut

through this area.

A Whole Town Devastated

Greensburg, Kansas was leveled by a tornado on

May 4, 2007.

The town of about 1,500 suffered 11

deaths.

Approximately 3 out of 4 Tornadoes Occur in the U. S.

Tornado Alley

The largest outbreak of

tornadoes in U. S. history occurred on April 3-4, 1974 in

the Ohio and Tennessee River Valleys. During a 16-hour period, a

total of 148 tornadoes killed

330 people.

THE SALT LAKE CITY TORNADO – AUGUST 11, 1999

A BLIZZARD is a heavy snowstorm with winds of more than 35 miles per

hour and reduced visibility. The greatest snowfall for a 24-hour period

was 76 inches in Silver Lake, Colorado in 1921. A snowstorm that lasted from

February 13-19, 1959 once dumped 189 inches, almost 16 feet of snow, on

Mt. Shasta, California.

Blizzards are dangerous for various reasons. They endanger people and

livestock who become trapped in them. They also snarl traffic, and

make travel conditions dangerous. In the Sierra Nevada and Rocky

Mountains, as well as the Great Lakes areas, hundreds of inches fall in a

season.

A DROUGHT is a long period of time without rain or with very minimal

rainfall. This lack of rainfall results in crop failures and reduced levels in

water storage facilities such as reservoirs. In extreme cases, this may cause people to move to new

areas in search of food, or to starve.

Five major factors that influence the climate of a region:

Wind Patterns

Ocean Currents

Latitude

Elevation

Topography

Global Wind

Patterns

Global Ocean Currents

Zones of LatitudeLow/Tropical

Middle/Temperate

High/Polar

Tropical ZonesThe tropical zones are found on both

sides of the equator, and go from the TROPIC OF CANCER to the TROPIC OF CAPRICORN.

Lands in the tropical zone are hot all year long.

Wind patterns may affect the amount of rainfall in areas.

http://upload.wikimedia.org/wikipedia/commons/4/4a/World_map_torrid.svg

Temperate ZonesThe temperate zones lie between

the tropical and polar zones.Climates range from relatively hot to

relatively cold.Variations occur because solar

heating is greater in the summer than in the winter.

http://upload.wikimedia.org/wikipedia/commons/0/0d/World_map_temperate.svg

Polar Zones In the northern hemisphere, it extends

from the ARCTIC CIRCLE to the NORTH POLE.

In the southern hemisphere, it extends from the ANTARCTIC CIRCLE to the SOUTH POLE.

It is cold all of the year, and summer temperatures may only reach 50°F.

http://upload.wikimedia.org/wikipedia/commons/9/95/World_map_frigid.svg

Elevation – Height Above Sea Level

As ELEVATION increases, the air temperature drops about 3.5°F every 1000 feet. Places over 12,000 feet in elevation share similar characteristics with polar zones. Some mountains near the equator have snow year-round.

TopographyLandforms also affect climate.

When moisture-filled winds move up the sides of mountains, they cool and release moisture. So on the

WINDWARD side of a mountain, it is greener. On the other side, it

does not receive as much moisture, and is known as the LEEWARD

side.

Windward/Leeward

The Two Biggest Factors in Determining Climate Are: Temperature and Rainfall

Monthly Average Temperatures Across the Planet

Monthly Average Rainfall Across the Planet

Major Climate Zones of the Earth

The darker the color red, the wetter these tropical areas are. Tropical areas can definitely be dry as well.

Tropical Dry in East-

Central Africa

Tropical Wet in South

America

The darker the color brown, the drier these desert areas are. They include the steppes, and rocky/sandy deserts.

The Steppes of Central

Asia

The rocky and sandy Sahara

of Africa

The color green represents the mild, mid-latitude zones, often with 4 distinct seasons. The darker green represents climates

that are even milder, sometimes called Mediterranean.

Springtime in D.C.

Turkish Coast

The color purple represents the severe mid-latitude zones. The darker purple represents 4-season climates that are

harsher. The lighter shade represents the cold sub-arctic.

Distinctive 4 Seasons in

New Hampshire

SubarcticAlaska

The color blue represents the polar or highland zones. The lighter blue represents the ice caps. Even mountainous

areas close to the equator share “polar” characteristics.

HighlandArea of India

Polar Region of Antarctica