Climate and Seasons

Unit 4

What is climate?

• Climate is the average weather usually taken over a 30+ year time period for a particular region.
• Climate is not weather — it is the average pattern of weather for a particular region.
• Weather describes a short-term state of the atmosphere.

What is our climate system?

• A region’s climate is generated by the climate system, which has five components: the atmosphere, hydrosphere, cryosphere, lithosphere, and biosphere.

Atmosphere (air)

• The atmosphere covers the earth. It is a thin layer of mixed gases that makes up the air we breathe. This thin layer also helps to regulate the Earth’s temperature, so that it doesn’t get too hot or too cold.

Hydrosphere (water)

• The hydrosphere of Earth represents the combined mass of water on the planet. Oceans cover over 70% of the Earth’s surface. Their large size and thermal properties allow them to store a lot of heat.

Lithosphere (land)

• The lithosphere of the Earth comprises of the crust and the upper mantle. Land covers 27% of Earth’s surface, and land topography influences weather patterns.

Cryosphere (ice)

• Earth’s cryosphere is made up of everything where water is in its solid form. This includes ice, snow, glaciers, and other forms of frozen water.
• Ice is the world’s largest source of fresh water. It covers the remaining 3% of Earth’s surface. Ice plays an important role in regulating climate, because it is highly reflective.

Biosphere (life)

• The biosphere is the part of the Earth’s atmosphere that supports any living plant, animal, or organism. It is the place where plants and animals, including humans, live.

Extra: Pedosphere (soil)

• The pedosphere is the outermost layer of Earth that contains soil. It is the meeting point (interface) of the atmosphere, hydrosphere, lithosphere, and biosphere, and only develops where there is a dynamic (moving) relationship among the 4 spheres. It is the foundation of all terrestrial life.

Climate Zones

• There are 5 climate zones: tropical, dry, moderate, continental, and polar.
• Each of the 5 climate zones have their own sub climate zones.
• Climate Zones: http://oceanservice.noaa.gov/education/pd/oceans_weather_climate/media/climate_zones.swf

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Tropical Climate Zone

• Tropical climates are usually found near the equator.
• There are two subcategories under the Tropical climate zone:
• Tropical Wet
• Tropical Wet and Dry

Tropical Wet

• Tropical wet climates are hot and muggy all year round. Heavy rainfall and thunderstorms are frequent, with these regions averaging from 70 to 100 inches per year. Temperatures do not fall below 64°F even during the coolest part of the year. These climates are usually found between 5 to 10 degrees north and south of the equator.

Tropical Wet and Dry

• Tropical wet and dry climates, also known as tropical savannas, have mostly warm to hot temperatures. Temperatures fluctuate moderately during the day and throughout the year. Areas with this climate receive moderate rainfall during the year, with wetter summers and drier winters. They are usually located on the edges of tropical wet climates.

Dry Climate Zone

• Dry climates are usually found in desert regions.
• There are two subcategories under the Dry climate zone:
• Arid
• Semiarid

Arid

• Arid climates are characterized by very hot summers and mild to cold winters. These areas have very little cloud cover and scarce rainfall throughout the year.

Semiarid

• Semiarid (or steppe) climates are like arid climates but more moderate temperatures. They typically surround desert areas. Rainfall is slightly higher than that of arid regions.

Moderate Climate Zone

• Moderate Climate Zones have three subcategories:
• Mediterranean
• Humid Subtropical
• Marine West Coast

Mediterranean

• Mediterranean climates have warm to hot and dry summers, and mild and rainy winters. These climates are usually found on coasts.

Humid Subtropical

• Humid Subtropical climates are characterized by warm to hot summers and cool winters. Rainfall is evenly distributed throughout the year.
• Humid Subtropical climates are usually found in the interiors of continents.

Marine West Coast

• Marine West Coast climates are only found on the western sides of continents because the wind direction is from sea to land. Winters are cool and mild, and summers are mild with moderate precipitation.

Continental Climate Zone

• Continental Climate Zones contain two subcategories:
• Humid Continental
• Subarctic

Humid Continental

• Humid Continental climates are characterized by mild to warm summers and cold winters. Precipitation is generally distributed evenly throughout the year.

Subarctic

• Subarctic climates have short, cool summers and long, bitterly cold winters. This climate receives most of its precipitation in the summer.

Polar Climate Zone

• The polar climate zone is divided into two categories:
• Tundra
• Ice Cap

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Tundra

• Tundra climates are dry with a brief, chilly summer and a bitterly cold winter. They occur on the northern edges of North America, Europe, and Asia.

Ice Cap

• Ice Cap climates are the coldest on Earth. Even in summer, temperatures rarely rise above the freezing point. Winter temperatures are extremely low and winter conditions are long and dark.

Highlands

• The highland climate is not defined with the main climate zones. These climates occur in mountainous regions, where elevation plays a role in the weather and climate. Each range of elevation has slightly different climate characteristics.

5 Factors that affect climate

• Latitude - the further you are from the equator, the cooler the temperatures.
• Wind/Air Masses - air masses carry the conditions from where they originate. If the wind comes from a colder area, it will lower temperatures. If the wind comes from a higher temperature, it will increase temperatures.

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5 Factors that affect climate

• Altitude/Elevation - the higher up you go, the colder it gets. This is because as elevation increases, the air becomes less dense. Less dense air cannot hold as much heat as dense air, meaning as elevation increases, temperature decreases.
• Distance to Water - large bodies of water have a moderating effect on temperature. Water warms and cools slower, so coastal regions have a lower difference in temperature throughout the year.

5 Factors that affect climate

• Landforms - landforms alter patterns of precipitation. The way they are shaped can increase or decrease sunlight exposure and can act as barriers or producers of different forms of precipitation.

Climate Graphs

• Climate Graphs are used to illustrate the average temperature and rainfall experienced at a particular place over the course of a year. The graphs consist of a red line graph showing average monthly temperature, and a simple column graph showing average monthly rainfall figures. Rainfall is shown in blue.
• Some graphs show both the average daily high and daily low temperatures. These graphs use a red line for high temperature and a blue line for low temperatures.

Examples of Climate Graphs

Reading Climate Graphs

• One side of the axis has temperature and the other has rainfall levels. Match the line graph with the temperature at any month, and bar graph with the rainfall.
• Don’t forget to look at the scales and units of the graph!

What causes weather?

• Because the Earth is round and not flat, the Sun's rays don't fall evenly on the land and oceans. The Sun shines more directly near the equator bringing these areas more warmth. However, the polar regions are at such an angle to the Sun that they get little or no sunlight during the winter, causing colder temperatures. These differences in temperature create a restless movement of air and water in great swirling currents to distribute heat energy from the Sun across the planet. When air in one region is warmer than the surrounding air, it becomes less dense and begins to rise, drawing more air in underneath. Elsewhere, cooler denser air sinks, pushing air outward to flow along the surface and complete the cycle.

How do mountains affect weather and climate?

• There are two sides to a mountain: windward and leeward. Whenever it is raining, the windward side gets the rain. As a cloud goes up the mountain, it keeps raining until there is no more water in the cloud. Now, as the cloud starts to go down the other side of the mountain, there is no more precipitation. So, the leeward side of the mountain doesn't get any rain. The flat ground on this side of the mountain is dry and humid.

Rain Shadow

• A rain shadow is a dry area on the leeward side of a mountainous area (away from the wind). The mountains block the passage of rain-producing weather systems and cast a "shadow" of dryness behind them.

Why do we have seasons?

• As the Earth spins on its axis, producing night and day, it also moves about the Sun in an elliptical (elongated circle) orbit that requires 365 1/4 days to complete. The Earth's axis is tilted at 23.5 degrees and is why we have seasons. When the Earth's axis points towards the Sun, it is summer for that hemisphere. When the Earth's axis points away, winter can be expected.

What is an equinox?

• An equinox occurs when the Earth is not tilted and the center of the Sun is directed at the equator. Daytime and nighttime are about equal in duration.

What is a solstice?

• A solstice happens when the Earth is tilted 23.5 degrees and the center of the Sun is directed at the Tropic of Cancer or the Tropic of Capricorn.
• The Tropic of Cancer is located at 23.5°N latitude, and the Tropic of Capricorn is located at 23.5°S latitude.
• The day of the solstice is either the longest day of summer or the shortest day of winter (depending on region and time).

Vernal Equinox

• On March 20-22, the sun is overhead at the equator. This marks the vernal equinox, and the beginning of spring in the Northern Hemisphere.
• For the Southern Hemisphere, the vernal equinox occurs in September. They have opposite seasons.
• Northern and Southern hemispheres have flipped seasons!

Autumnal Equinox

• On September 21-23, the sun is overhead at the equator. This marks the autumnal equinox, and the beginning of fall in the Northern Hemisphere.
• For the Southern Hemisphere, the autumnal equinox occurs in March. They have opposite seasons.
• Northern and Southern hemispheres have flipped seasons!

Summer Solstice

• The summer solstice happens during a hemisphere’s summer. In the Northern Hemisphere, this takes place on June 20-22, while in the Southern Hemisphere, this takes place on December 20-22. It is the longest day of the year.

Winter Solstice

• The winter solstice happens during a hemisphere’s winter. In the Northern Hemisphere, this takes place on December 20-22, while in the Southern Hemisphere, this takes place on June 20-22. It is the shortest day of the year.

Why is the sun important?

• Without the sun, there would be no weather. Our planet is located at the perfect distance to suit life.

Telling time with the sun

• The sun always rises in the east and sets in the west. Because of this, the sun’s location in the sky and give you an approximation of the time.

Why do we get more sunlight in the summer?

• The location of the sun determines the length of day. During the winter months, the hemisphere is pointed away from the sun, so it takes a shorter time for the sun to move from horizon to horizon. In the summer months, the hemisphere is pointed toward the sun, so it takes longer for the sun to travel across the horizon, resulting in longer daytimes.

The Moon

• The tidal effect of the moon helps recirculate the oceans.
• The moon creates high tides and low tides depending on its position.

Why do leaves change color?

• During the spring and summer the leaves have served as factories where most of the foods necessary for the tree's growth are manufactured. This food-making process takes place in the leaf in numerous cells containing chlorophyll, which gives the leaf its green color. Along with the green pigment are yellow to orange to red pigments as well. Most of the year these colors are masked by great amounts of green coloring. But in the fall, because of changes in the length of daylight and changes in temperature, the leaves stop their food-making process. The chlorophyll breaks down, the green color disappears, and the yellow to orange to red colors become visible and give the leaves part of their fall splendor. The best time to enjoy the autumn color would be on a clear, dry, and cool day.

Climate Change

• Climate change represents a change in long-term weather conditions. It can be illustrated with a change in temperature or a change in precipitation amounts.

Global Warming

• Global warming refers to an average increase in the Earth's temperature, which in turn causes changes in climate. A warmer Earth may lead to changes in rainfall patterns, a rise in sea level, and a wide range of impacts on plants, wildlife, and humans. When scientists talk about the issue of climate change, their concern is about global warming caused by human activities.

The Greenhouse Effect

• The greenhouse effect is the rise in temperature that the Earth experiences because certain gases in the atmosphere like water vapor, carbon dioxide, nitrous oxide, and methane trap energy from the sun. Without these gases, heat would escape back into space and Earths average temperature would be about 60ºF colder and would not be warm enough for humans to live. But if the greenhouse effect becomes stronger, it could make the Earth warmer than usual.

Deforestation

• Deforestation is the cutting down large numbers of trees to use the land for something instead of a forest. Cutting down trees can affect the climate. After rain falls on a forest, mist rises and new rain clouds form. When forests are cut down, this cycle is disrupted, and the area eventually grows drier, causing a change in the local climate. If huge areas of trees are cut down, the carbon dioxide they would have used builds up in the atmosphere and contributes to the greenhouse effect. And without trees to hold the soil and absorb water, rain washes topsoil away, a process called soil erosion.

Erosion

• Erosion is the wearing away of the land by water, ice or wind. Soil erosion is a natural process. It becomes a problem when human activity causes it to occur much faster than under natural conditions. Wind and water are the main agents of soil erosion.

Acid Rain

• Acid rain is rain, snow or fog that is polluted by acid in the atmosphere and damages the environment. Two common air pollutants acidify rain: sulphur dioxide and nitrogen oxide. When these substances are released into the atmosphere, they can be carried over long distances by prevailing winds before returning to earth as acidic rain, snow, fog or dust. When the environment cannot neutralize the acid being deposited, damage occurs.