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Earth Science 21.2 World Climates World Climates.

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Presentation on theme: "Earth Science 21.2 World Climates World Climates."— Presentation transcript:

1 Earth Science 21.2 World Climates World Climates

2 Earth Science 21.2 World Climates  If you were to travel around the world, you would find an incredible variety of climates.  So many climates in fact, that one might find it hard to conceive that they could all occur on one planet.  Despite this diversity, climates can be classified according to their average temperatures, and amounts of precipitation.  In this lesson, we will examine the Koppen climate classification system.

3 Earth Science 21.2 World Climates The Koppen Climate Classification System:  Many classification systems have been used to classify climates.  Perhaps the best known and most commonly used system is the Koppen Climate Classification System.  The Koppen climate classification system uses mean monthly and annual values of temperature and precipitation to classify climates.  This system is often used because it classifies the world into climatic regions in a realistic way.

4 Earth Science 21.2 World Climates  The Koppen system has five principal groups Humid tropical climates Dry climates Humid mid-latitude climates Polar climates highland climates  All of these groups, except those classified as dry, are defined on the basis of temperature.  Dry climates are classified partly according to the amount of precipitation that falls over an area.  Each of these five major groups is than subdivided further.

5 Earth Science 21.2 World Climates Humid Tropical Climates  Humid tropical climates are climates without winters.  Every month in such a climate has a mean temperature above 18 degrees Celsius.  There are two types of tropical climates ○ Wet tropical climates ○ Dry tropical climates

6 Earth Science 21.2 World Climates Wet Tropical Climates  The tropical rain forests of Costa Rica are typical of a wet tropical climate.  Wet tropical climates have high temperatures and much annual precipitation.  Recall what we have already learned about how latitude effects climate.  The intensity of the sun’s rays in the tropics is consistently high.  Because the sun is directly overhead much of the time, changes in the length of daylight throughout the year are very slight.

7 Earth Science 21.2 World Climates Wet Tropical Climates  The wind that blows over the tropics cause the warm, humid, unstable air to rise, cool, condense, and fall as precipitation.  Note that these areas of wet tropical climates fall on a belt centered on the equator when one looks at a world climate map.

8 Earth Science 21.2 World Climates Tropical Wet and Dry Climates:  Bordering the wet tropics are climates classified as tropical wet and dry climates.  Tropical wet and dry climates have temperatures and total precipitations similar to those in the wet tropics, but experience distinct dry seasons (periods of no or little rain).  Savannas, which are tropical grasslands with drought resistant trees, are typical of tropical wet and dry climates.  An African savanna can be seen at right.

9 Earth Science 21.2 World Climates Humid Mid-latitude climates:  Humid mid-latitude climates fall into two groups: Climates with mild winters Climates with severe winters  Climates with mild winters have an average temperature in the coldest month that is below 18 degrees Celsius but above -3 C.  Climates with severe winters have an average temperature in the coldest month that is below -3C.

10 Earth Science 21.2 World Climates Humid Mid-latitude climates:  There are three types of humid mid-latitude climates: Humid subtropical Marine west coast climates Dry-summer subtropical climates

11 Earth Science 21.2 World Climates  Located between 25 degrees and 40 degrees latitude on the eastern sides of continents are the humid subtropical climates.  Notice that a humid subtropical climate dominates the southeastern side of the United States.  In the summer, these areas experience hot, humid weather as daytime temperatures often soar.  Although winters here are generally mild, frosts are common in the higher latitude areas.  The temperatures and precipitation data in the graph at right are typical of a subtropical climate.

12 Earth Science 21.2 World Climates  Coastal areas between about 40 degrees and 65 degrees north and south latitude have marine west coast climates.  Maritime air masses over these regions result in milder winters and cool summers with an ample amount of rainfall throughout the year.  In North America, the marine west coast climate extends as a narrow belt from northernmost California into southern Alaska.  The data table at right for Vancouver shows average temperature (in red) and precipitation (in blue) amounts for this zone.

13 Earth Science 21.2 World Climates  Regions with dry-summer subtropical climates are generally located between 30 degrees and 45 degrees latitude.  These climatic regions are unique because they are the only humid climate that has a strong winter rainfall maximum.  In the United States, dry summer subtropical climate is found only in California.  It is sometimes referred to as a Mediterranean climate.

14 Earth Science 21.2 World Climates Humid Mid-latitude with severe winters:  There are two types of humid mid- latitude climates with severe winters: the humid continental climates and the subarctic climates.  Continental landmasses strongly influence both of these climates.  As a result, both of these climates are absent from the Southern Hemisphere. There, oceans dominate the mid-latitude zone.

15 Earth Science 21.2 World Climates Humid Mid-latitude with severe winters:  Looking at the map at right we can see that the winter temperatures are quite severe while the summers are warm.  Note as well that precipitation is generally greater in the summer than the winter.

16 Earth Science 21.2 World Climates Humid Mid-latitude with severe winters:  North of the humid continental climate and south of the tundra is an extensive subarctic continental climate region. (show in purple)  This climate zone covers a large swath of North America, stretching from western Alaska to Newfoundland in North America.

17 Earth Science 21.2 World Climates Humid Mid-latitude with severe winters:  Winters in these regions are long and bitterly cold.  In contrast, summers in the subarctic areas are relatively warm but very short.  The extremely cold winters and warm short summers combine to produce the highest annual temperature ranges on Earth.

18 Earth Science 21.2 World Climates Dry Climates:  A dry climate is one in which the yearly precipitation is not as great as the potential loss of water by evaporation.  The dryness of a climate is not only related to the amount of rain that falls; it also is based on the amount of evaporation of water that takes place within the zone.  Evaporation, in turn, is heavily linked to the temperature of an area.  There are two types of dry climates: arid (desert) and semi-arid climates (steppe).

19 Earth Science 21.2 World Climates Dry Climates:  Arid and semi-arid climates have much in common between them.  In fact, the difference between them is actually very slight.  The steppe is a marginal, slightly more humid variation of the desert environment.  The steppe is a transition zone that isolates the desert and creates a transition between it and the more livable humid climates.

20 Earth Science 21.2 World Climates Dry Climates:  Dry climates exist as the result of the global distribution of air pressure and winds.  In regions near the Tropics of Cancer and Capricorn, air is subsiding, sinking from above.  When air sinks, it becomes compressed and warms. These conditions are the exact opposite of the conditions that produce rain clouds.  As a result, these regions experience clear, sunny skies and dry climates with little rain.

21 Earth Science 21.2 World Climates Dry Climates:  Other dry areas of the world include the Gobi Desert in Africa, the Great Basin of North America and the Sahara desert.  These arid areas are called rain shadow deserts.  Some of the Earth’ driest climates occur where a cold ocean current effects the west coast of a continent.  A cold current cools the air above it. This strengthens the sinking of air in the warm, dry air masses that cause deserts.  The Namib desert of Africa is an example of this type of dry coastal desert.

22 Earth Science 21.2 World Climates Polar Climates:  Polar climates are those in which the mean temperature of the warmest month is below 10 degrees Celsius.  Polar winters are periods of perpetual night, or nearly so.  During the summer, temperatures remain cool despite the long hours of daylight.  Very little precipitation falls in polar regions.

23 Earth Science 21.2 World Climates Polar Climates:  There are two types of polar climates: the tundra climate and the ice cap climate.  The tundra climate is a treeless region found almost exclusively in the Northern Hemisphere.  The ice cap climate does not have a single monthly mean above 0 degrees Celsius. The landscape is covered with permanent snow and ice.  Ice cap climates occur in high mountain areas and in Greenland and Antarctica.

24 Earth Science 21.2 World Climates Highland Climates:  Highland climates are localized.  This means they are much different from climates in nearby surrounding areas.  Conditions of highland climates often vary abruptly from one place to another.

25 Earth Science 21.2 World Climates Highland Climates:  For example, southern facing slopes are warmer than north facing slopes, and air on the windward sides of mountains is wetter than air on the leeward sides of mountains.  In general, highland climates are cooler and wetter than nearby areas at lower elevations.

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