1. Chapter 10 Global Climate Systems
Geosystems 6e
An Introduction to Physical Geography
Robert W. Christopherson
Charles E. Thomsen

2. 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!).

3. Earth’s 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

4. Climatic Relationships
Figure 10.3

5. 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

6. Climate Classification
Genetic classification: based on what major air masses and global circulations that dominate the climate idealized continent approach
Empirical classification: based on comparisons of climate variables, such as precipitation changes from season to season
statistics!

7. 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

8. 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

9. Köppen’s Climate Classifications
Primary Letters
Tropical Climates (A)
Average temp of every month > 18ºC
Mesothermal Climates (C)
Coldest month average temperature < 18ºC but >-3ºC
At least 1 month average temperature > 10ºC
Microthermal Climates (D)
Average temperature of warmest month >10ºC
Average temperature of coldest month < -3ºC

10. Köppen’s Climate Classifications
Primary Letters
Polar Climates (E)
Average temperature of all months  < 10ºC
Dry Arid and Semiarid Climates (B)
Evaporation > precipitation
Highland (H)

11. Köppen’s 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.

12. Köppen’s 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.

13. Köppen’s Climate Classifications
Tertiary Letters
The third letters in the system are based exclusively on seasonal and annual temperature:
a = hot summer, warmest month > 22°C; C and D only
b = warm summer, warmest month < 22°C; C and D only
c = cool summer, < 4 months over 10°C; C and D only
d = very cold winter, coldest month < -38°C; D only
h = dry-hot, annual temperature > 18°C; B only
k = dry-cold, annual temperature < 18°C; B only

14. Köppen’s 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

15. Generalized Climate Regions
Figure 10.4

16. World Climate Classification
Figure 10.5

17. Climographs
Temperature (curve)
Precipitation (bars)

18. Climatic Relationships
Figure 10.3

19. 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

20. Tropical Rain Forest and Monsoon

21. Tropical Rain Forest (Af)
Figure 10.7

22. Tropical Monsoon (Am)
Figure 10.8

23. Tropical Monsoon Climate (Am)
Figure 6.21

24. Tropical Savanna (Aw)

25. Aw Tropical Savanna

26. Af Tropical Rain Forest

27. Am Tropical Monsoon

28. Arid and Semiarid Climates (B)
Figure 10.3

29. Arid and Semiarid Climates (B)
Köppen system:
W = Desert (arid), S = Steppe (semiarid)
h = hot (mean annual temp > 18°C)
usually found in lower latitudes
k = cold/cool (mean annual temp < 18°C)
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)  

30. Arid and Semiarid Climates (B)
Potential for evaporation exceeds rainfall (called “moisture efficiency”)
Cover 35% of Earth’s 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

31. 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

32. Arid and Semiarid Climates (B)

33. Low-Latitude Hot Desert Climate (BWh)

34. Midlatitude Cold Desert Climate (BWk)

35. Low-latitude hot steppe (BSh)

36. Midlatitude cold steppe (BSk)

37. BWh Low-latitude hot desert

38. BSk Midlatitude cold steppe