Section 1.2 The Causes of Weather Science 10

1. What three things affect the distribution of solar energy that reaches the Earth? Three things that affect the distribution of solar energy that reaches the Earth are the curved surface, the tilt, and the orbit of the Earth.

2. Using figure 1.11 on page 26, explain why areas closer to the equator are warmer than areas closer to the poles. When sun hits the poles it is more spread out over a larger area which means that it is less concentrated so areas do not heat up as much. When the sun’s light hits the areas closer to the equator it is very concentrated over a small area so the warming effect is much greater.

3. Explain how the tilt of the Earth affects seasonal changes. As the Earth orbits the sun the tilt of the poles changes and this affects the weather in those regions. When the northern hemisphere is tilted toward the sun, the solar energy strikes the surface of the Earth more directly and the temperature is very warm. When the northern hemisphere is tilted away from the sun there is a less direct contact of solar energy and much cooler temperatures result.

4. How can the shape of the Earth’s orbit around the sun affect the length and intensity of the seasons? Earth’s orbit around the sun may be circular or oval and it changes every 100 000 years. The amount of solar energy the Earth gets varies more when the orbit is oval and the seasons will be longer and more intense. A circular orbit means that the solar energy is more constant and the seasons will be more balanced.

5. How does an air mass form and where do most of them form? An air mass forms when air close to the ground is heated by conduction and the warmed air rises. The resulting air mass often has the same properties such as temperature, humidity and pressure as the land it formed over. Most air masses form over tropical or polar regions.

6. What is the difference between an air mass that forms over the interior of Canada and an air mass that forms over the North Atlantic Ocean? An air mass that forms over the interior of Canada is known as a Continental Polar air mass and it will be very cold and dry during the winter and cool and dry during the summer. An air mass that forms over the North Atlantic Ocean is known as a Maritime Polar air mass and it will be cold and humid during the winter and the summer.

7. Explain how a high pressure system develops. A high pressure system develops when an air mass cools over an ocean or a cold region on land. The cooling of air particles causes them to become more dense, the air mass contracts pulling in more air and the extra weight increases pressure. This causes the air mass to move outward towards low pressure area (wind). The rotation of the Earth causes the air to circulate in a clockwise direction, the air sinks and becomes warmer and drier. High pressure systems usually bring clear skies.

8. Explain how a low pressure system develops. A low pressure system develops when air masses traveling over warm land or oceans warms up, expands and rises increasing the thickness of the layer of air. As the warm air rises it cools, condenses and forms clouds or precipitation. While this is occurring the expanding air mass is pushing away air high in the troposphere, air pressure near the surface of the Earth decreases and this draws in air from high pressure areas. The rotation of the Earth causes the air in a low pressure system to curve and the wind flows counter clockwise in a northern hemisphere and clockwise in the southern hemisphere.

9. What is the Coriolis Effect and how does it impact wind? The Coriolis Effect is a change in the direction of moving air, water, or any object’s on the Earth’s surface due to its rotation. The Coriolis effect causes air that is circulating to be deflected in different directions in the northern (right) and southern (left) hemispheres.

10. What are the three major wind systems and what is their general path? Location Path Trade Winds Between the equator and 30° north latitude. Between the equator and 30° south latitude. Air at the equator warms, rises and travels to 30° north or south latitude. At 30° north or south the air cools, sinks, and moves west toward the equator and is deflected west. Prevailing Westerlies Between 30° and 60°north latitude. Between 30° and 60° south latitude. Air circulation pattern is opposite to that of the trade winds. Surface winds blow from west to east and toward the poles. Polar Easterlies Between 60° north latitude and the North Pole. Between 60° north latitude and the South Pole. Air circulation pattern is similar to that of the trade winds. Surface winds blow from east to west and away from the poles.

11. What is a jet stream? Identify the major and minor jet streams. A jet stream is a narrow band of fast moving wind and its speed varies with the temperatures of air masses at the wind zone barriers. The major jet streams are known as the polar jet streams and they separate the polar easterlies from the prevailing westerlies. The minor jet streams are known as the subtropical jet streams and they occur where the prevailing westerlies meet the trade winds.

12. What is a front and what does an approaching front mean in terms of weather? A front is a zone that develops as a result of the meeting of two air masses with different characteristics. An approaching front indicates that there will be a change in the weather and the severity of the change will depend on the difference between the conditions of the two air masses. Also, fronts usually bring precipitation.

13. Identify the 4 types of weather fronts that may form. The four types of weather fronts that may form are: Cold front Warm front Stationary front Occluded front

14. What is a thunderhead and how does it form? Thunderheads are large cumulonimbus clouds that form when water vapour in rising warm air condenses and releases thermal energy. The released thermal energy warms the air even further and it continues to rise. The resulting thunderheads take on a typical anvil shape and can produce heavy rains, hail and lightening.

15. What is a tornado and how does it form? A tornado is a violent, funnel-shaped column of rotating air that touches the ground. They form when high altitude horizontal winds meet large thunderstorms. The horizontal winds cause the rapidly rising air in the thunderstorm to rotate and produces a funnel cloud, which may touch the ground and become a tornado.

16. Why are the tropics an ideal location for the formation of intense storms? The tropics are the ideal location for the formation of intense storms due to the warm ocean water and winds. Warm moist air gets lifted into the atmosphere where it condenses and produces precipitation and clouds. The precipitation release large amounts of thermal energy, the rising air produces a low pressure area near the surface of the water, warm air rushes in and the Coriolis effect causes the air to rotate creating a massive spinning storm.

17. What are the three types of tropical cyclones and where do each of them occur? Tropical cyclones in areas near the Indian Ocean are known as cyclones. Tropical cyclones that form near the Western Pacific Ocean are known as typhoons. Tropical cyclones that form in the Atlantic Ocean are known as hurricanes.