Physical Geography 101

Temperature - Heat

Temperature is a measure of heat
Kinetic energy; Thermal energy
Related to motion of atoms.
Faster motion = higher temperature
Slower motion = lower temperature


Heat always flows:
- from warmer areas to cooler areas
- high energy areas to lower energy areas
Heat is transferred by:

Temperature Measurements

Temperature is measured using:
Thermometers: Expansion or contraction of a liquid (mercury, alcohol) or metal (spring coil)
Thermistors: Electronic changes in resistance of an electrical current.
Charged Couple Device (CCD): Electronic measure of infrared radiation emitted.

Temperature Scales

Daniel Gabriel Fahrenheit - °F (1717)
Based on: ice melting at 32° and a human body temperature being equal to 96° (98.6°F)
Water freezes at ____° F
Water boils at ____°F

Temperature scales

Anders Celsius - °C (1742)
International System of Units (SI)
Water freezes at ____°C
Water boils at ____°C

Absolute Temperature Scales

Atoms are always in motion
Absolute Zero: Temperature at which all motion stops.
no heat energy
Absolute Temp. Scale: Kelvin – K (SI)
K = °C + 273.15°

Daily Temperature Variation

Daily Insolation
Net Radiation

Amount of energy gained or lost during the day
There is a net gain during the day, at night a net loss.

Daily Temperature

Minimum temp.: just after sunrise
Max. temperature: mid-afternoon

Surface Temperature Variations

Air temperature over different surfaces:
Dark surfaces absorb more radiation.
– Air above will be warmer
Light surfaces reflect more radiation.
– Air above will be cooler

Urban Areas vs. Rural Areas

Urban Heat Island: warmer temperatures
– Dark buildings, asphalt, water drained beneath the surface, air conditioners and engines
Rural Areas: cooler temperatures
– Soil, vegetation, moisture in the soil


Additional Information

The Earth Observer, Sept-Oct 2006 Issue: Within this PDF document is an article entitled "There's a Change in Rain Around Desert Cities" by Rob Gutro. It highlights some new research results in regards to Urban Heat Islands.