1. Part 6. Current, Past, and Future Climates
Chapter 15
Earth’s Climates

2. Introduction
Climate is the long-term statistical properties of the atmosphere for an area
Climate classifications are based on properties such as temperature, precipitation, air mass types, and water budget characteristics

3. The Koeppen climate classification system
Most widely used classification scheme
Based on natural vegetation types as indicators of average weather

5. Koeppen Classifications

6. Tropical Climates
Warm annual temperatures and minimal seasonal temperature variation
Differentiated on precipitation variations
Tropical Wet (Af)
Even precipitation through year
High humidity
Temperatures
Highs = low 30°s C (80°s F)
Lows = low 20°s C (70°s F)

7. Af climographs
Monsoonal effects seen in the precipitation trends throughout the year

8. Monsoonal (Am)
Near tropical coastal areas
Monthly precipitation variations are significant, with very high annual totals
Small annual temperature variations

9. (strong monsoonal precipitation)
Am climographs
(strong monsoonal precipitation)

10. Tropical Wet and Dry (Aw)
Poleward tropical margins
Distinct temperature and precipitation seasonality
Low sun dry period
Unreliable precipitation
Sahel region
Savanna vegetation

11. Aw climographs

12. Dry Climates 30% of Earth’s land surface Defined by water balance
Potential evapotranspiration > precipitation
Subtropical Deserts (BWh)
Largest deserts
Western sides of continents
Areas with atmospheric subsidence
High diurnal temperature ranges (low dew points/humidity)

13. BWh climographs

14. High precipitation variability of BWh regions
Southern California site; 1983 and 1992 were El Nino years

15. Subtropical Steppe (BSh)
High aridity
High precipitation and temperature variability
Large temperature ranges
Extreme summer temperatures
Summer precipitation

16. BSh climographs

17. Mid-Latitude Deserts (BWk)
Extreme continentality and/or rain shadows
Asia and the Western U.S.
Very high temperature ranges
Summer temperatures – very hot
Nighttime and winter temperatures - very cool
Higher humidity and precipitation

18. BWk climographs

19. Mid-Latitude Steppe (BSk)
A transition zone
Higher annual average precipitation than true desert

20. BSk climographs

21. Mild Mid-Latitude Climates
Eastern continental areas
Varying precipitation regimes
Mild winter temperatures
Summer temperatures may be high

22. Mediterranean (Csa, Csb)
Distinct summer dry period
Subtropical high interactions
Winter precipitation is variable
Mild winter temperatures
Mild to hot summers

23. Csa, Csb climographs

24. Humid Subtropical (Cfa, Cwa)
Eastern continental areas of the lower mid-latitudes
High heat and moisture
Abundant and even monthly precipitation
Weather influenced by subtropical highs
Mild winters
Hot summers

25. Cfa, Cwa climographs

26. Marine West Coast (Cfb, Cfc)
Poleward of Csb
Cold ocean current influence
Often has fog and/or low cloud cover
Mild and even annual temperatures
High frequency of rain days

27. Cfb, Cfc climographs

28. Severe Mid-latitude Climate
Very cold winters
Large continental areas
Evenly distributed annual precipitation
Humid Continental (Dfa, Dfb, Dwa, Dwb)
Eastern continents - 40o-55o N
Warm to hot summers
Cold winters
Even and abundant annual precipitation

29. Dfa, Dfb, Dwa, Dwb climographs

30. Subarctic (Dfc, Dfd, Dwc, Dwd)
Poleward of humid continental climates
Coniferous boreal forest (taiga)
Warm, short summers
Low annual precipitation (summer maximum)

31. Dfc, Dfd, Dwc, Dwd climographs

32. Polar Climates Very high latitudes Very cold Tundra (ET)
Tundra vegetation
Harsh winters
Mild summers of long days
Permafrost region

33. ET climographs

34. Ice Cap (EF)
Constant ice cover
Greenland and Antarctica
Warmest monthly temperatures < 0oC
Katabatic winds
Low precipitation

35. EF climographs

36. Highland Climates (H) Governed solely by topography Vertical zonation
Highly variable local climates

37. End of Chapter 15 Understanding Weather and Climate 4th Edition Edward Aguado and James E. Burt