Chapter 5 Global Temperatures

1. Chapter 5Global Temperatures Geosystems 6e An Introduction to Physical Geography Robert W. Christopherson Charles E. Thomsen

2. Global Temperatures • Temperature Concepts    • Principal Temperature Controls   • Earth’s Temperature Patterns 

3. Heat vs. Temperature • Heat and Temperature are not the same thing • Heat: a form of energy that flows from one system or object to another because the two are at different temperatures • Temperature: a measure of the average kinetic energy (motion) of individual molecules in matter

4. Principal Temperature Controls • Latitude • Altitude • Cloud Cover • Land-Water Heating Differences

5. Latitude and Temperature • Latitude   • Affects insolation • Sun angles • Daylength Figure 5.4

6. Altitude • Altitude   • High altitude has greater daily range • High altitude has lower annual average Figure 5.5

7. Cloud Cover • Clouds moderate temperatures • At night, clouds act as insulators and reradiate longwave energy • During the day, clouds reflect insolation because of high albedo

8. Land–Water Heating Differences  • 5 land-water temperature controls: • Evaporation (= latent heat) • Transparency (= penetration of insolation) • Specific heat (differs among objects) • Movement (= vertical mixing) • Ocean currents and sea surface temperatures(= spread of energy spatially)

9. Land-Water Heating Differences • Evaporation • Marine locations experience evaporative cooling • When water evaporates, it absorbs heat from the immediate environment lowing temperatures

10. Land-Water Heating Differences • Transparency • Solid ground is opaque, water is transparent • Energy is absorbed by the soil surface during the day and is released at night • Light transmits through water on average 200 ft – this area of light is called the photic layer • Because water can absorb energy to a greater depth, it forms a large energy reservoir

11. Land-Water Heating Differences • Specific heat • The ability of a substance to absorb energy • Oceans have higher mass and higher specific heat than land, so oceans experiences increases and decreases in heat more slowly • It takes more energy to raise the temperature of ocean water

12. Land-Water Heating Differences • Movement • Water is fluid and land is not • Water can move energy and land cannot • Water releases longwave radiation at a slower rate than land does

13. Land-Water Heating Differences • Ocean Currents and SST • Warm water adds energy to overlying air through high evaporation rates and transfers latent energy • Ocean currents transfer energy surpluses to areas of energy deficits • Land cannot move energy – there are no land currents

14. Land–Water Heating Differences   Figure 5.7

15. Land Is Opaque Figure 5.8

16. The Gulf Stream Figure 5.10

17. The Gulf Stream • Energy is lost from oceans in the form of latent heat – water evaporates, energy is absorbed in water vapor, energy is lost from oceans • As water vapor increases in the air, the air’s ability to absorb water vapor increases • The warmer the air mass gets, the more evaporation occurs, which leads to cloud formation

18. The Gulf Stream • Clouds reflect insolation and produce lower temperatures, this reduces evaporation rates and the ability of the air to absorb water vapor • Negative feedback – response slowed in a system

19. Marine vs Continental Effect • Marine effect (or maritime) describes locations that exhibit the moderating influences of the ocean, usually along coastlines or on islands • Continental Effect (or continentality) refers to areas less effected by the sea and therefore having a greater range of temperatures on a daily and yearly basis

20. Marineand Continental Climates Figure 5.12

21. Marineand Continental Climates Figure 5.13

22. Earth’s Temperature Patterns • Isotherm – an isoline (a line of constant value) that connects points of equal temperature • Thermal equator – isotherm connecting all points of highest mean temperature • January Temperature Map   • Thermal equator movement southward • More pronounced over large continents • July Temperature Map   • Thermal equator movement northward • More pronounced over large continents

23. January Temperatures Figure 5.14

24. July Temperatures Figure 5.16

25. Global Temperature Ranges Figure 5.17