Lesson 5 Thermal Energy and Climate
The Biomes
How does thermal energy transfer and topography affect the biomes?
©NRC
D5.17 Topography map of Canada
D5.17 Topography map of Canada
Topography is what the land looks like.
This includes the location of mountains, large bodies of water, and large, flat spaces. These physical characteristics of the land, as well as thermal energy transfer, can have a large effect on the biomes we previously looked at. Before we look at the effects of those physical characteristics, there are two things we need to know or remember:
-
Cooler air cannot hold as much moisture as warmer air; so as air cools, the moisture in the air condenses and forms precipitation.
- Warm air rises and cool air moves in to replace it, creating convection current, or wind.
D5.18 Land and sea breezes
There are two main types of wind caused by large bodies of water. One is called a sea breeze and the other a land breeze.
A sea breeze is a breeze that blows in from the large body of water. As the sun rises, the land will heat up faster than the water, since the land has a lower specific heat capacity. As the land warms, it transfers its thermal energy to the air above it, making that air warm faster than the air over the water. Since the air over the land is warmer, it rises and the cooler air from the water moves in to replace it. The warm air is pushed out over the water where it cools down and sinks. It then moves back to the land where it warms up again.
A land breeze is the opposite of a sea breeze; a land breeze blows out toward the large body of water. This occurs at night after the sun has set. The land will cool down faster than the water, again due to its specific heat capacity. As the land cools, it will take the thermal energy from the air, causing the air over the land to cool faster than the air over the water. Since the air over the water is warmer, it rises and the cool air from the land moves out over the water. It then warms up and rises. Once it rises, it is pushed back to the land where it cools and sinks back down.
These breezes help to reduce the variation in temperature of these coastal regions by evening out the thermal energy between the water and land. Remember, the temperatures can be warmer or colder than other areas depending on if the body of water is warmer or colder.
A land breeze is the opposite of a sea breeze; a land breeze blows out toward the large body of water. This occurs at night after the sun has set. The land will cool down faster than the water, again due to its specific heat capacity. As the land cools, it will take the thermal energy from the air, causing the air over the land to cool faster than the air over the water. Since the air over the water is warmer, it rises and the cool air from the land moves out over the water. It then warms up and rises. Once it rises, it is pushed back to the land where it cools and sinks back down.
These breezes help to reduce the variation in temperature of these coastal regions by evening out the thermal energy between the water and land. Remember, the temperatures can be warmer or colder than other areas depending on if the body of water is warmer or colder.
D5.19 Rain in Victoria, BC
Being close to a large body of water will also increase the amount of moisture in the air, as there is more water to evaporate into the air. This can affect how cold a temperature feels. Victoria, British Columbia, has an average temperature of 4 ˚C in the winter, but it often feels much colder due to the amount of moisture in the air. On the other hand, Edmonton, Alberta, has an average temperature of –14 ˚C in the winter, but it may not seem as cold because it is much dryer.
The amount of moisture in the air also affects the amount of precipitation that is seen. As the air cools, it cannot hold onto the moisture as well and so that moisture turns into precipitation. Coastal cities such as Victoria and Vancouver, which are close to a warmer body of water, see large amounts of rain, especially in the wintertime. This is because the land is cooler than the ocean; so as the air cools over the land, the air releases the moisture it is carrying in the form of lots of rain.
On the east coast of Canada, where the ocean is cooler, the air releases the moisture as snow. Places such as New Brunswick see an average of 2 to 3 m of snow each year. Alberta sees an average of 0.7 to 2 m.
On the east coast of Canada, where the ocean is cooler, the air releases the moisture as snow. Places such as New Brunswick see an average of 2 to 3 m of snow each year. Alberta sees an average of 0.7 to 2 m.
D5.20 Snow on the east coast
But why is Edmonton so much dryer than Victoria? Alberta is not that far from the ocean, so shouldn’t we have at least a bit of the moisture that BC sees? The answer to these questions has to do with the Rocky Mountains.
As the air moves farther up the mountains, it cools down, releasing the moisture it is still carrying as precipitation. By the time the air reaches the Alberta side of the mountains, it does not contain much moisture. The air now moves down the mountains, warming up as it goes. There is very little chance to pick up more moisture, so the air remains very dry and produces very little precipitation. This is called a rain shadow. The warm, dry air that comes off the mountains is often referred to as a chinook. A great example of a region in a rain shadow is southern Alberta, including Calgary, Lethbridge, Medicine Hat, and Pincher Creek.
A rain shadow can occur in any place located downwind from mountains. This means that the cities are located in the direction the wind is blowing. If the wind blows to the east (such as over the Rockies, as they have westerlies blowing over them), then the cities to the east of the mountains will see a rain shadow.
Did You Know?
Did You Know?
As the air moves farther up the mountains, it cools down, releasing the moisture it is still carrying as precipitation. By the time the air reaches the Alberta side of the mountains, it does not contain much moisture. The air now moves down the mountains, warming up as it goes. There is very little chance to pick up more moisture, so the air remains very dry and produces very little precipitation. This is called a rain shadow. The warm, dry air that comes off the mountains is often referred to as a chinook. A great example of a region in a rain shadow is southern Alberta, including Calgary, Lethbridge, Medicine Hat, and Pincher Creek.
A rain shadow can occur in any place located downwind from mountains. This means that the cities are located in the direction the wind is blowing. If the wind blows to the east (such as over the Rockies, as they have westerlies blowing over them), then the cities to the east of the mountains will see a rain shadow.
Did You Know?
D5.22 Chinooks cause high winds
The strongest chinook in Lethbridge occurred on November 19, 1962, with gusts up to 171 km/h.
Did You Know?
D5.23 A month of chinooks
The areas of Pincher Creek, Crowsnest Pass, and Lethbridge see 30 to 35 chinook days per year. That is a month’s worth of chinook.
Take Notes
Make sure you take notes on your readings to study from later. You should focus on how topography affects the weather in certain geographical locations on Earth. Remember, if you have any questions or you do not understand something, ask your teacher!
Practice Questions
Complete the following practice questions to check your understanding of the concept you just learned. Make sure you write complete answers to the practice questions in your notes. After you have checked your answers, make corrections to your responses (where necessary) to study from.
-
How does a sea breeze occur?
A sea breeze happens as the sun rises and warms up the land faster than the sea. The warm air over the land then rises, and the cool air from the sea comes in to replace it. The warm air is pushed out over the sea where it cools and heads back toward the land. This creates a wind that blows from the sea onto the land.
-
How do mountains affect the climate of the cities that lay down wind of them?
Mountains create a dryer climate in cities that lay down wind from them.
- What happens to the amount of moisture in the air as it cools?
The amount of moisture in the air drops as the air cools. This is because the air cannot hold onto the moisture, so it is turned into precipitation.