Chapter 10 Global Climate Systems

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Chapter 10Global Climate Systems

• Geosystems 6e
• An Introduction to Physical Geography

Robert W. Christopherson Charles E. Thomsen
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Climate

• Climate is weather averaged over time over
  broader geographic areas.
• Usually averaged over 30-yr periods.
• Climatology is the study of climate over both
  time and space.
• One central goal is to determine climatic
  regions, areas with similar weather statistics.
• Another central goal is to analyze climate
  variability over time (like global warming!).

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Earths Climate System and Classification  

• Climate Components
• Insolation
• Temperature
• Pressure
• Air Masses
• Precipitation  
• These help the classification of climatic
  regions.
• By using 2 principal climatic components,
  temperature and precipitation, general climate
  types are revealed

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Climatic Relationships
Figure 10.3
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Climate Classification

• Provides an organized and manageable source of
  information that simplifies rather complex
  patterns in the real world
• Also gives us a common short hand way to describe
  climates quickly and easily
• There are 2 approaches to climate classification
  genetic and statistical

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Climate Classification

• Genetic classification based on what major air
  masses and global circulations that dominate the
  climateidealized continent approach
• Empirical classification based on comparisons of
  climate variables, such as precipitation changes
  from season to season
• statistics!

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Empirical Classification

• Koppen climate classification
• Developed 1918
• Developed to correlate the spatial distribution
  of plants to the spatial distribution of climate
• The Koppen-Geiger climate classification system
  is the updated version in your text

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Koppen-Geiger

• Statistical climate classification based on
  average monthly temperatures, average monthly
  precipitation, and total annual precipitation
• Takes seasonality into account
• Drawbacks omits winds, temperature extremes,
  precipitation intensity, amount of insolation,
  and cloud cover

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Köppens Climate Classifications
Primary Letters

• Tropical Climates (A)
• Average temp of every month gt 18ºC
• Mesothermal Climates (C)
• Coldest month average temperature lt 18ºC but
  gt-3ºC
• At least 1 month average temperature gt 10ºC
• Microthermal Climates (D)
• Average temperature of warmest month gt10ºC
• Average temperature of coldest month lt -3ºC

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Köppens Climate Classifications
Primary Letters

• Polar Climates (E)
• Average temperature of all months  lt 10ºC
• Dry Arid and Semiarid Climates (B)
• Evaporation gt precipitation
• Highland (H)

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Köppens Climate Classifications
Secondary Letters

• These letters are based primarily on seasonal
  precipitation
• f adequate rainfall all through the year, no
  distinct dry season
• w winter dry (keep in mind the hemisphere), if
  70 or more of annual rainfall occurs in summer
• s summer dry, if 70 or more of annual rainfall
  occurs in winter
• m extremely wet summer monsoon. A climate
  only.

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Köppens Climate Classifications
Secondary Letters

• For B climate only
• S semiarid steppe
• W arid desert
• which results in either BS or BW.
• For E climate only
• T tundra
• F perpetual frost permanent ice
• which results in either ET or EF.

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Köppens Climate Classifications
Tertiary Letters

• The third letters in the system are based
  exclusively on seasonal and annual temperature
• a hot summer, warmest month gt 22C C and D
  only
• b warm summer, warmest month lt 22C C and D
  only
• c cool summer, lt 4 months over 10C C and D
  only
• d very cold winter, coldest month lt -38C D
  only
• h dry-hot, annual temperature gt 18C B only
• k dry-cold, annual temperature lt 18C B only

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Köppens Climate Classifications
Examples of Combinations

• Af Tropical Rainforest climate type
• Am Tropical Monsoon climate type
• BWh Low-Latitude Hot Desert climate type
• Cfa Humid Subtropical climate type
• Csa Mediterranean climate type
• Dfb Humid Continental climate type
• ET Tundra climate type

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Generalized Climate Regions
Figure 10.4
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World Climate Classification
Figure 10.5
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Climographs
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Climatic Relationships
Figure 10.3
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Tropical Climates (A)

• Tropical Rain Forest Climates (Af)  
• Tropical Monsoon Climates (Am)  
• Tropical Savanna Climates (Aw)
• Consistent daylength and insolation input
• consistent warm temperatures
• Dominance by ITCZ
• Shifts seasonally with high sun period
• Warm ocean currents, unstable maritime air masses

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Tropical Rain Forest and Monsoon
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Tropical Rain Forest (Af)
Figure 10.7
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Tropical Monsoon (Am)
Figure 10.8
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Tropical Monsoon Climate (Am)
Figure 6.21
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Tropical Savanna (Aw)
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Aw Tropical Savanna
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Af Tropical Rain Forest
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Am Tropical Monsoon
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Arid and Semiarid Climates (B)
Figure 10.3
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Arid and Semiarid Climates (B)

• Köppen system
• W Desert (arid), S Steppe (semiarid)
• h hot (mean annual temp gt 18C)
• usually found in lower latitudes
• k cold/cool (mean annual temp lt 18C)
• usually found in the midlatitudes
• Low-Latitude Hot Desert Climates (BWh)  
• Midlatitude Cold Desert Climates (BWk)  
• Low-Latitude Hot Steppe Climates (BSh)  
• Midlatitude Cold Steppe Climates (BSk)  

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Arid and Semiarid Climates (B)

• Potential for evaporation exceeds rainfall
  (called moisture efficiency)
• Cover 35 of Earths surface
• Most extensive geographically of the major
  climate groups
• One-third of U.S. is classified as arid/semiarid
• Plants are sparse but specifically adapted
• Xerophytes adapted to aridity, drought
  resistant, able to store moisture

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Arid and Semiarid Climates (B)

• Climatic controls
• STHP dry subsiding air over land masses
• Shifting STHP produces semiarid conditions
  around periphery of arid areas
• Rain shadows leeward sides of mountain ranges
  that intercept rainfall on windward side
• Continentality interiors of continents far from
  moderating effects of water bodies

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Arid and Semiarid Climates (B)
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Low-Latitude Hot Desert Climate (BWh)
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Midlatitude Cold Desert Climate (BWk)
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Low-latitude hot steppe (BSh)
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Midlatitude cold steppe (BSk)
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BWh Low-latitude hot desert
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BSk Midlatitude cold steppe