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Chapter 3 :The Changing Weather

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1 Chapter 3 :The Changing Weather
What Is a Snowstorm? Two factors are essential in the creation of a snowstorm: snow and wind Snow forms when water vapour condenses at a temperature below the freezing point. As it condenses it forms ice crystals that join together and make snowflakes.

2 Chapter 3 The Changing Weather
Snow pg. 34 Condensation: the process by which moisture in the air changes to liquid or solid form. Examples are rain, clouds, and snowflakes. Condensation occurs when moist air rises and cools. It then forms clouds.

3 Chapter 3 : The Changing Weather
Snow Pg. 34 Air may rise for several reasons: it may be blown over high ground, it may be warmed from below and rise, or it may be forced upward by a colder and denser air mass.

4 You may think that areas that get the greatest snowfalls would see schools close most often however average snowfall is not a reliable predictor of storms

5 Chapter 3 The Changing Weather
Snow pg. 34 The second ingredient-wind-is essential to a storm. Snow drifting down in soft white flakes generally does not pose much of a danger to traffic. However, propel that snow with fast-moving air and it may become a blizzard that is hazardous to most forms of transportation

6 Chapter 3: The Changing Weather
Wind pg. 36 Wind is air that is moving from an area of high pressure to an area of low pressure. High Pressure: an atmospheric condition caused by the sinking of cool air Low Pressure: an atmospheric condition caused by rising of warm air

7 Chapter 3 - The Changing Weather
Wind pg. 36 Hot air rises cool air sinks A warm surface will heat the air above it causing it to rise. This creates an area of low pressure beneath the rising air. An area of high pressure occurs when the cool air sinks towards the earth’s surface and pushes the air underneath it away.

8 Chapter 3 The Changing Weather
You're well familiar with our "H" and "L" designations on weather maps for areas of high and low pressure, but what do they mean in regards to what weather's coming? High pressure situations are generally associated with fair, sunny weather. As high pressure is an area of sinking air, and air tends to dry out as it sinks, leaving sunny skies. Low pressure areas are generally cloudy/rainy areas -- where strong areas of low pressure bring our stormiest weather. That's because it's an area of rising air, and as air rises, it condenses into clouds and rain. Air moves from higher pressure to lower pressure, so if you have a high and a low nearby, it can be windy as air rushes between the two

9 Chapter 3 The Changing Weather

10 Chapter 3 : The Changing Weather
Air at the poles sinks because it is cold. Air at the equator rises because it is warm. So how does that affect weather in the Atlantic Region. These air masses do not stay in one place because of the earth’s rotation.

11 Chapter 3: The Changing Weather
Climate: average conditions of temperature, precipitation, humidity, air pressure, and wind Precipitation: rain, snow, and any other forms of water particles that fall from the atmosphere Weather: conditions of the atmosphere over a short period

12 Chapter 3: The Changing Weather
4 Factors That Influence the Climate of Atlantic Canada: Latitude Air masses Ocean currents Proximity to water

13 Chapter 3 : The Changing Weather
All parts of the world receive the same total number of daylight hours over a year. The earth’s surface is curved so sunshine is more intense in lower latitudes How does this influence climate? Cape Sable, Nova Scotia at 43*N receives more intense sun than Killinek, Labrador at 60*N

14 Chapter 3 : The Changing Weather
Air Masses are… large volumes of air with similar temperature and moisture conditions throughout Air masses take on the temperature and humidity characteristics of the areas in which they originate For example, when Maritime Tropical air comes in from the Caribbean it feels warm and moist Air masses, like wind, move because of changing pressure

15 Chapter 3 : The Changing Weather
The leading edge of an air mass is known as a front. Front: The leading edge of an air mass, bringing characteristics of the air mass; they often result in a change in temperature Most precipitation in the Atlantic Region comes about when cold dry air from the north meets warm moist air from the south.

16 Chapter 3 : The Changing Weather
Ocean Currents: the movement of water in the world’s oceans Water in the oceans is constantly in motion; tides move the water up and down-ocean currents move water from place to place. The two currents that affect the Atlantic Region most are the Gulf Stream and the Labrador Current

17 Chapter 3 : The Changing Weather
Gulf Stream: an Atlantic Ocean current from the south; it brings warmth to the southwestern waters of the Atlantic provinces Labrador Current: an ocean current from the north; it brings cold waters to much of the Atlantic coast

18 Chapter 3 : The Changing Weather
When the two currents meet fog is often the Result. The warm moist air of the Gulf Stream Is cooled and condenses. The water vapor droplets are not large enough to fall as rain so they remain suspended in the slowly moving air.

19 Chapter 3 : The Changing Weather
4/ Proximity to the Ocean Sunshine heats land and water at different rates: Water, and the air over it, heats up and cools down more slowly than land. As a result areas close to large bodies of water stay cooler in the summer and warmer in the winter than areas that are inland This affects the climate of many Atlantic towns close to the ocean.

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