Download Air Temperature

Air Temperature
►Temperature
:
 a measure of the average
speed at which molecules are
moving or vibrating.
►Air
temperature
 the rate of motion of gas
molecules in the
atmosphere as a result of
the absorption of energy
 measured by a thermometer
Temperature scales
► Celsius
 water freezes at 0o
 water boils at 100o
► Fahrenheit
 water freezes at 32o
 water boils at 212o
► Kelvin
 no molecular motion at 0 K
 water freezes at 273 K
 water boils at 373 K
Conversions
►oF
= (1.8 x oC) + 32
►oC
= 0.56 (oF - 32)
►K
= oC + 273
What determines the temperature
of a place?
1.
Insolation
(daily and annual cycles)
2. Latitude
3. Urban/Rural Surface
4. Coastal vs. Interior location
5. Elevation
1. Insolation
A. Changing angle of noon sun
throughout the year changes
temperature on a seasonal basis.
►Why
temperature difference
between equinoxes?
►
Spring : at end of cold, short
day period
 more energy loss
►Autumn
: at end of warm, long
day period
 more energy gain
1. Insolation
B. Changing angle of sun
throughout the day changes
temperature on a daily basis.
►lag
between max insolation and
max temperature
 because highest temp at time of
max ABSORBED insolation
2. Latitude
► Higher
latitudes receive less insolation
than lower latitudes
 sun’s rays are more oblique
 daylength is variable
 Net energy surplus in tropics; net energy
deficit in polar regions
3. Urban/rural Surface
► Evapotranspiration
differences
► Urban impervious surfaces
► Urban highly absorbent (low albedo)
surfaces
► Urban fuel consumption and excess heat
► “Urban
heat island”
4. Coastal vs. interior locations
►Water
bodies have a moderating
effect on temperature.
► “Land
heats up and cools down more
rapidly than water.”
 Therefore:
►Coastal: smaller temperature
ranges than continental
locations.
►Coastal
locations have their
maximum temperatures well
after maximum insolation.
►Lake
effect in Duluth is an example
of changes in temperature due to
being close to a large body of water.
5. Altitude / Elevation
►Temperature
decreases as elevation
increases.
 less mass, less
pressure, less
absorption
Exception: temperature inversion
►Conditions
favorable for a
temperature inversion:
 cool, clear, calm night