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Section 3
Climate and Weather
Prepare To Read
Objectives
In this section you will
1. Learn about weather and climate.
2. Explore latitude, landforms, and precipitation.
3. Discover how oceans affect climate.
Taking Notes
As you read this section, look for topics related to climate and weather, such as
landforms, precipitation, oceans, and storms. Copy the outline below and add
headings as needed to show the relationships among these topics.
Target Reading Skill
Use Context Clues You can sometimes learn the meaning of a word or phrase
when the context gives a comparison. In this example, the word cyclone is
compared to the phrase in italics.
A cyclone is like a huge spiral escalator moving air upward.
Key Terms
weather (WETH ur) n. the condition of the air and sky from day to day
precipitation (pree sip uh TAY shun) n. water that falls to the ground as rain,
sleet, hail, or snow
temperature (TEM pur uh chur) n. how hot or cold the air is
climate (KLY mut) n. the average weather over many years
tropical cyclone (TRAHP ih kul SY klohn) n. an intense wind and rain storm that
forms over oceans in the tropics.
Chapter 2, Section 3
Weather or Climate?
Every morning, most people check the weather before they get dressed. But in
some parts of India, people have very serious reasons for watching the weather,
or the condition of the air and sky from day to day. In parts of India, it rains
only during one time of year. No one living there wants the rainy days to end too
soon. That rain must fill the wells with enough fresh water to last for the entire
year.
In India, people are concerned about precipitation, or water that falls to the
ground as rain, sleet, hail, or snow. When you get dressed in the morning, you
may want to know the temperature, or how hot or cold the air is. Weather is
mainly measured by temperature and precipitation.
The climate of a place is the average weather over many years. Climate is
not the same as weather. Weather is what people see from day to day. Climate is
what usually happens from year to year.
This Inuit woman and child are dressed for their cold climate.
Reading Check
What is the difference between weather and climate?
Chapter 2, Section 3
Why Climates Vary
Earth has many climates. Some climates are so hot that people rarely need to
wear a sweater. In some cold climates, snow stays on the ground most of the
year. And there are places on Earth where more than 30 feet (9 meters) of rain
falls in a single year.
Climate depends on location. Places in the low latitudes, or tropics, have hot
climates, because they get direct sunlight. Places in the high latitudes, or polar
regions, have cold climates, because their sunlight is indirect.
Air and water spread heat around the globe as they move. Without wind and
water, places in the tropics would overheat. Oceans gain and lose heat slowly, so
they keep temperatures mild near coasts. Mountains can also affect climates.
Cherrapunji, India, averages 37 feet (11 meters) of rain a year.
Chapter 2, Section 3
Oceans and Climates
The oceans help distribute Earth’s heat and shape climates. Global wind patterns
help create ocean currents, which are like vast rivers in the oceans. Ocean
currents move across great distances. Generally, warm water flows away from
the Equator, while cold water moves toward the Equator.
Target Reading Skill
Using Prereading Strategies If you do not know what ocean currents are,
notice that they are compared to vast rivers in the ocean. How does the
comparison help you find the meaning?
Oceans and Currents
In the Atlantic Ocean, the Gulf Stream, a warm current, travels northeast from the
tropics. The Gulf Stream and the North Atlantic Current carry warm water all the
way to western Europe. That warm water gives western Europe a milder climate
than other regions at the same latitude.
The cold Peru Current moves north from Antarctica along the coast of South
America. The city of Antofagasta (ahn toh fah GAHS tah) lies along that coast, in
Chile. Even though Antofagasta is closer than Miami, Florida, is to the Equator,
the average temperature in Antofagasta during the hottest month of summer is
just 68°F (20°C).
The Ocean’s Cooling and Warming Effects
Bodies of water affect climate in other ways, too. Water takes longer to heat or
cool than land. As the air and land heat up in summer, the water remains cooler.
Wind blowing over the water cools the nearby land. So in summer, a region near
an ocean or lake will be cooler than an inland area at the same latitude. In the
winter, the water remains warmer than the land. So places near lakes or oceans
are warmer in winter than inland areas.
Consider San Francisco, California, and St. Louis, Missouri. Both cities are near
38° north latitude. However, San Francisco borders the Pacific Ocean. In winter,
the ocean is warmer than the air. The ocean keeps San Francisco much warmer
than St. Louis in winter. In summer, the ocean is cooler than the air, so it keeps
San Francisco cool.
Chapter 2, Section 3
Raging Storms
Wind and water can make climates milder, but they also can create large and
dangerous storms. Tropical cyclones are intense wind and rain storms that
form over oceans in the tropics. Tropical cyclones that form over the Atlantic
Ocean are called hurricanes. The -winds near the center of a hurricane can
reach speeds of more than 100 miles (160 kilometers) per hour. Hurricanes
produce huge swells of water called storm surges, which flood over shorelines
and can destroy buildings.
Hurricane Andrew In 1992 Hurricane Andrew caused massive destruction and left 160,000 people
homeless in south Florida. Synthesizing Information Is a hurricane more likely on a tropical coast or in a
polar region far from the ocean?
Tornadoes are like funnels of wind that can reach 200 miles (320 kilometers) per
hour. The winds and the low air pressure they create in their centers can wreck
almost anything in their path. They can be just as dangerous as hurricanes, but
they affect much smaller areas.
Other storms are less dangerous. In winter, blizzards dump huge amounts of
snow on parts of North America. And severe rainstorms and thunderstorms strike
the continent most often in spring and summer.
Reading Check
Which storms cover larger areas, hurrricanes or tornadoes?