Physical Geography: GEOG 1301

Spring 2005

Chapter 5: Global Temperatures

Throughout this chapter consider the effects and possible causes of increasing world temperatures.

Important Concepts

Heat- form of energy that flows between objects/systems because they are at different temperatures

Temperature: measure of the average kinetic energy of individual molecules in matter

Both are related because changes in temperature are caused by absorption or emission of heat energy.

Fantastic Web Site about Temperature:

http://www.unidata.ucar.edu/staff/blynds/tmp.html

NASA Introduction to Temperature Scales:

http://cryowwwebber.gsfc.nasa.gov/introduction/temp_scales.html

Principal Temperature Controls

1. Latitude:. Related to the energy surplus/deficit patterns from equator to poles.

Most important influence!!!

2. Altitude: Temperature decreases as altitude increases (normal lapse rate.) As atmosphere thins, the ability to absorb and radiate heat is reduced- average air temp. is lower and nighttime cooling is greater (at high altitude.)

3. Cloud Cover: 50% of Earth cloud covered at any given moment. Moderate temperature and their moisture reflects, absorbs and liberates large amounts of energy. Lower daily maximum temperatures and raise nighttime temperatures. Most variable factor influencing Earth’s weather.

4. Land-water heating Differences: differences in heating by insolation. Caused by physical nature of land and water. (See 5 land-water temperature controls.)

The 5 Land-water Temperature Controls

1. Evaporation: consumes more energy over the ocean surface than over land- 84% of evaporation is over oceans. Surface water evaporation lowers temperature

2. Transparency: Light striking soil does not penetrate, is absorbed, heating ground surface. Light transmits through water to 200ft- Distribution of heat over a larger area- larger energy reservoir.

3. Specific Heat: water requires more energy to increase its temperature than land. Water (higher specific heat) can hold more energy than rock or soil. Water requires more time to loss heat energy

4. Movement: Mixing of water spreads available energy. Retains energy more than land.

5. Ocean Currents and Sea-surface Temperatures: Negative feedback- warmer air creates more evaporation creates more clouds (more water vapor) which reflects insolation and lowers temperature.

Marine vs. Continental Effects

Marine effects are more moderate while continental effects are more extreme

Alexander von Humboldt – theory of continentality

http://geography.about.com/library/weekly/aa020298.htm

A simple overview:

http://www.ecn.ac.uk/Education/factors_affecting_climate.htm

Earth Temperature Patterns (Causes and Ranges: Why really cold or really hot)

Isotherm- isoline that connects points of equal temperature.

Thermal Equator- isoline connecting points of highest mean temperature. The tend is east-west and parallel to the equator- except over land masses where they follow the effects of continentality. Understand Figure 5.14 (page 131) and 5.16 (page 133.)

Know January and July temperature patterns

Key Terms

· Heat versus temperature

· Land-water heating differences

· Marine & continental effect

· Isotherm

· Thermal Equator