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10.2 Water’s Influence on Weather and Climate
(See Student Book pages 290–297)
How Water Moderates Air Temperature
Heat Capacity
It can take a kettle of water a long time to boil and a cup of tea or broth a while to cool
down. These examples demonstrate an important physical property of water: it has a high
heat capacity. Heat capacity is the ability of a substance to absorb heat. It takes
a lot of energy to heat water. But water can hold that heat longer than air or land.
The water in a kettle takes a long time to boil.
Hot water takes a long time to cool down.
If you have gone swimming in a lake in early summer, you found that the water was quite
cold, while the land around it was warmer. Land (soil) has a lower heat capacity than
water. The land requires less energy from the Sun to heat up, though it releases
(or loses) its heat faster than water.
List three facts about the heat capacity of water.
It takes a lot of energy to heat water. Water absorbs heat slowly. Water releases heat slowly.
Water has a higher heat capacity than air or land.
List three facts about the heat capacity of land.
It takes less energy to heat land than to heat water. Land absorbs heat faster than water.
It releases heat faster than water. The heat capacity of land is less than that of water.
Moderation in Action
The fact that land and water absorb and release heat at different rates has interesting effects
on the climate of a region.
On a hot summer day, you may have noticed that the second floor of a house is warmer
than the first floor. This is because heat rises. Hot air is less dense and is lighter than cold
air, so it can easily rise. Cold air is heavier and does not rise.
Investigating Science and Technology 7 & 8
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The right to reproduce this page is restricted to the purchasing school.
All of Earth’s precipitation results from how hot and cold air behave. Hot air, which
contains water vapour, rises.
Cooler air then blows in and takes the place of the hot air that has left the area. This allows
coastal areas to stay cool. When the cold air warms up and becomes hot air, it too will rise.
At night, the air over the land cools fairly quickly, while the air over the water stays warm,
providing heat to the land.
Look at the illustrations below. On the lines below, write what you think is happening in
each illustration.
During the day, the land gets hotter than the
As the Sun goes down, the land cools off
nearby water. The air above the land rises.
quickly, but the water does not. Some of the
Cooler air from over the water rushes in to take
heat stored in water moves into the air, and this
the place of the rising air.
warmed air begins to rise. The cooled air over
the land moves in to take the place of the rising
warm air over the water.
The land absorbs heat from the Sun more quickly than the water does. The air over the land
becomes warmer as some of this absorbed heat is radiated back into the air. The warmer air
begins to rise, and the cooler air over the water moves in to take its place.
Water Bodies and Regional Climate
Around the world, large bodies of water affect the climate from one region to another. For
example, the Great Lakes have a strong effect on the land nearby. These huge bodies of
water send large amounts of moisture into the air through evaporation. In winter, the extra
moisture prevents the air from becoming as cold as it would otherwise. Eventually, the
extra moisture condenses and falls as rain or snow.
Microclimates
Winter comes later for people living close to the Great Lakes than it does for those who
live farther from shore. Warm air from lakes keeps nighttime temperatures above freezing
for a longer period of time than for inland locations. This kind of climatic effect is called a
microclimate. A microclimate is an area with a climate that differs somewhat from the
climate of the area around it.
Investigating Science and Technology 7 & 8
Copyright © 2010 Pearson Canada Inc.
The right to reproduce this page is restricted to the purchasing school.
Water Bodies and Global Climate
Look at the map of the world. The southern
hemisphere has much more water surrounding
the continents than the northern hemisphere does.
Which hemisphere probably has the more
unchanging climates? Explain your answer.
The southern hemisphere probably has more unchanging climates because the large amounts
of water near land will keep the temperatures on land from changing very much.
Coastal Storms
Hurricanes are powerful storms that can take shape when an air mass moves across a large
body of warm water, such as the Gulf of Mexico. A hurricane is the strongest kind of storm
that we experience. Wind speeds are very high, and there is usually flooding rain. Powerful
winter storms also develop over large bodies of water, such as the Great Lakes. The
interaction of water and air over the lakes create high winds and lots of precipitation.
Look at the map above. Why do you think land along the coast of an ocean or large lake
has more powerful storms?
Land on the coast will have more storms, since more water can evaporate, condense, and fall as
precipitation through the cycling of water.
Key Term
microclimate: a small area that has a different climate than the rest of the area around it
Investigating Science and Technology 7 & 8
Copyright © 2010 Pearson Canada Inc.
The right to reproduce this page is restricted to the purchasing school.