World Geography 3200 Chapter 4 Weather and Climate

Weather & Climate (p.54) Weather: the day-to-day or short-term atmospheric conditions Weather: the day-to-day or short-term atmospheric conditions Variables would include temperature, precipitation, humidity, cloud cover, wind, air pressure Variables would include temperature, precipitation, humidity, cloud cover, wind, air pressure Climate: the weather patterns over a long period of time Climate: the weather patterns over a long period of time Variables would include temperature, moisture, air movement Variables would include temperature, moisture, air movement

The Earth-Sun Relationship (p.55) The sun provides enough heat to energize Earth and keep it warm. The sun provides enough heat to energize Earth and keep it warm.

The Earth-Sun Relationship The sun exerts a gravitational pull on the Earth, so Earth revolves around the sun. The sun exerts a gravitational pull on the Earth, so Earth revolves around the sun.

The Earth-Sun Relationship The Earth is tilted in its orbit, which partially explains the patterns of day and night and the seasons. The Earth is tilted in its orbit, which partially explains the patterns of day and night and the seasons. Because of the tilt, there are only 2 times a year when the sun shines equally on both hemispheres; March and September These are called equinoxes. Because of the tilt, there are only 2 times a year when the sun shines equally on both hemispheres; March and September These are called equinoxes.

Patterns in Temperature The range between daytime and nighttime temperatures results from: The range between daytime and nighttime temperatures results from: The amount of cloud cover in the sky The amount of cloud cover in the sky The earth’s curvature The earth’s curvature At the equator, sunlight comes directly through the atmosphere and strikes the earth directly, hitting a small area (fig 4.3, E) At the equator, sunlight comes directly through the atmosphere and strikes the earth directly, hitting a small area (fig 4.3, E) Away from the equator, sunlight comes through the atmosphere at an angle and strikes the earth indirectly, hitting a larger area (fig. 4.3, F) Away from the equator, sunlight comes through the atmosphere at an angle and strikes the earth indirectly, hitting a larger area (fig. 4.3, F)

Wind: The Movement of Air Air Circulation Pattern: Air Circulation Pattern: The air above the equator heats up rapidly and rises, pushing cooler air towards the north and south poles. The cooler this air gets, the more it sinks. As it sinks, it heats up and forces cooler air back towards the equator…and the pattern repeats… The movement pattern is called a convection cell, which more evenly distributes heat around the world. Convection Cells

Wind: The Movement of Air Convection is driven by air density: Convection is driven by air density: Warm, moist air is less dense and it floats Warm, moist air is less dense and it floats = Low pressure areas = Low pressure areas Cold, dry air is dense and it sinks Cold, dry air is dense and it sinks = High pressure areas = High pressure areas Wind is created when air moves from high pressure areas to low pressure areas Wind is created when air moves from high pressure areas to low pressure areas Questions: # 15 & 16, pages Questions: # 15 & 16, pages

Wind: The Movement of Air Prevailing Winds Prevailing Winds There are 6 convection cells which create a series of high and low pressure belts around the earth between which the wind blows. These wind patterns are constant and predictable There are 6 convection cells which create a series of high and low pressure belts around the earth between which the wind blows. These wind patterns are constant and predictable Trade Winds Trade Winds Westerlies Westerlies Polar Easterlies Polar Easterlies

Wind: The Movement of Air

Prevailing Winds (…continued) Prevailing Winds (…continued) Two factors change how prevailing winds blow: Two factors change how prevailing winds blow: Variations in the Earth’s surface (constant). Variations in the Earth’s surface (constant). The Earth’s position relative to the sun (varies by season) The Earth’s position relative to the sun (varies by season)

Wind: The Movement of Air Prevailing Winds (…continued) Prevailing Winds (…continued) Two factors complicate the pattern of convection currents: Two factors complicate the pattern of convection currents: The Earth’s surface The Earth’s surface The uneven distribution of land and water over the Earth’s surface The uneven distribution of land and water over the Earth’s surface Two factors complicate the pattern of convection currents: Two factors complicate the pattern of convection currents: The Earth’s surface The Earth’s surface The uneven distribution of land and water over the Earth’s surface The uneven distribution of land and water over the Earth’s surface

Wind: The Movement of Air Prevailing Winds (…continued) Prevailing Winds (…continued) Each hemisphere is broken up into 3 different convection cells (fig 4.10, p.63): Each hemisphere is broken up into 3 different convection cells (fig 4.10, p.63): degrees latitude degrees latitude degrees latitude degrees latitude 66.5-polar latitude 66.5-polar latitude

Wind: The Movement of Air Wind & Precipitation Patterns: Wind & Precipitation Patterns: Humidity: amount of moisture in the air; it comes from the earth’s surface and evaporates into the atmosphere.

Wind: The Movement of Air Wind & Precipitation Patterns (continued…) Wind & Precipitation Patterns (continued…) 2 Basic Principles about Precipitation : 2 Basic Principles about Precipitation : 1. When warm air cools, it cannot hold as much water vapour. 2. Temperature rises as air pressure increases; it lowers as air pressure decreases. *Do questions 22-26, p.64-67*

Other Factors Affecting Climate Ocean Currents: permanent or semi-permanent horizontal movement of unusually cold or warm surface water of the oceans, to a depth of about 100m. The primary cause of ocean currents is the global movement of winds. Ocean Currents: permanent or semi-permanent horizontal movement of unusually cold or warm surface water of the oceans, to a depth of about 100m. The primary cause of ocean currents is the global movement of winds. Three main factors influence how and where ocean currents flow… Three main factors influence how and where ocean currents flow…

Other Factors Affecting Climate Ocean Currents 1. Coriolis Effect: ocean currents shift left or right depending on the hemisphere they’re in.

Other Factors Affecting Climate Ocean Currents 2. The Size and shape of the body of water in which they develop. Ex. The Gulf Stream is deflected northeast by the shape of the North American coastline. Ex. The Gulf Stream is deflected northeast by the shape of the North American coastline.

Other Factors Affecting Climate Ocean Currents 3. Differences in water temperature and salt content (remember the effect this had in, ‘The Day After Tomorrow’?). These differences cause convection currents similar to those in the atmosphere.

Other Factors Affecting Climate Ocean Currents

Section questions: 27-30, pages Section questions: 27-30, pages 68-69

Other Factors Affecting Climate Continentality Continentality Water heats up and cools down more slowly than land. Water heats up and cools down more slowly than land. Areas near large bodies of water (Vancouver, Botwood) have a maritime climate; the temperature ranges are small and they have more precipitation. Areas near large bodies of water (Vancouver, Botwood) have a maritime climate; the temperature ranges are small and they have more precipitation. Areas far away from water (Calgary, Buchans) have a continental climate; the temp. ranges are large and they have less precipitation. Areas far away from water (Calgary, Buchans) have a continental climate; the temp. ranges are large and they have less precipitation.

Other Factors Affecting Climate Continentality and Wind Patterns Continentality and Wind Patterns Because the sun’s heat is retained differently by land and water… Because the sun’s heat is retained differently by land and water… Winds blow differently in coastal areas than in continental areas. Winds blow differently in coastal areas than in continental areas. Winds blow differently in mountainous areas than on the plains. Winds blow differently in mountainous areas than on the plains.

Other Factors Affecting Climate Elevation and Climate Elevation and Climate =height above sea level…the higher it is, the colder the climate is. =height above sea level…the higher it is, the colder the climate is.

Other Factors Affecting Climate Elevation also affects precipitation: Elevation also affects precipitation: Clouds must rise to pass over mountains. As they do, the water vapour in them condenses and rain/snow falls on the windward side. The leeward side (rain shadow) receives little precipitation.

Other Factors Affecting Climate Elevation and Climate Elevation and Climate Section Questions: page 71-72, #36b., 37, 38, 39, Section Questions: page 71-72, #36b., 37, 38, 39, Chapter review questions: page 72, # Chapter review questions: page 72, # 40-41