Air TemperatureAir Temperature

►Temperature :Temperature :

a measure of the average a measure of the average speed at which molecules are speed at which molecules are moving or vibrating.moving or vibrating.

►Air temperatureAir temperature the rate of motion of gas the rate of motion of gas

molecules in the molecules in the atmosphere as a result of atmosphere as a result of the absorption of energythe absorption of energy

measured by a thermometermeasured by a thermometer

Temperature scalesTemperature scales

►CelsiusCelsius water freezes at 0water freezes at 0oo

water boils at 100water boils at 100oo

►FahrenheitFahrenheit water freezes at 32water freezes at 32oo

water boils at 212water boils at 212oo

►KelvinKelvin no molecular motion at 0no molecular motion at 0 KK water freezes at 273 Kwater freezes at 273 K water boils at 373 Kwater boils at 373 K

ConversionsConversions

►ooF = (1.8 x F = (1.8 x ooC) + 32C) + 32

►ooC = 0.56 (C = 0.56 (ooF - 32)F - 32)

►K = K = ooC + 273C + 273

What determines the temperature What determines the temperature of a place?of a place?

1.1. Insolation Insolation (daily and annual cycles)(daily and annual cycles)

2. Latitude2. Latitude

3. Urban/Rural Surface 3. Urban/Rural Surface

4. Coastal vs. Interior location4. Coastal vs. Interior location

5. Elevation5. Elevation

1. Insolation1. Insolation

A.A. Changing angle of noon sun Changing angle of noon sun throughout the yearthroughout the year changes changes temperature on a temperature on a seasonalseasonal basis.basis.

►WhyWhy temperature difference temperature difference between equinoxesbetween equinoxes??

► Spring Spring : at end of cold, short : at end of cold, short day periodday period more energy loss more energy loss

►AutumnAutumn : at end of warm, long : at end of warm, long day periodday period more energy gainmore energy gain

1. Insolation1. Insolation

B.B. Changing angle of sun Changing angle of sun throughout the daythroughout the day changes changes temperature on a temperature on a dailydaily basis. basis.

►lag between max insolation and lag between max insolation and max temperaturemax temperature

because highest temp at time of because highest temp at time of max ABSORBED insolation max ABSORBED insolation

2. Latitude2. Latitude

►Higher latitudes receive less insolation Higher latitudes receive less insolation than lower latitudesthan lower latitudes

sun’s rays are more sun’s rays are more obliqueoblique daylength is daylength is variablevariable Net energyNet energy surplussurplus in tropics; in tropics; net energy net energy

deficitdeficit in polar regions in polar regions

3. 3. Urban/ruralUrban/rural Surface Surface

►Evapotranspiration differencesEvapotranspiration differences►Urban impervious surfacesUrban impervious surfaces►Urban highly absorbent (low albedo) Urban highly absorbent (low albedo)

surfacessurfaces►Urban fuel consumption and excess Urban fuel consumption and excess

heatheat

►““Urban heat island”Urban heat island”

4. Coastal vs. interior locations4. Coastal vs. interior locations

►Water bodies have a moderating Water bodies have a moderating effect on temperature.effect on temperature.

►““Land heats up and cools down more Land heats up and cools down more rapidly than water.”rapidly than water.”

Therefore:Therefore:►CoastalCoastal: : smaller temperature smaller temperature

rangesranges than continental locations. than continental locations.

►Coastal locations have their Coastal locations have their maximum temperatures well after maximum temperatures well after maximum insolation.maximum insolation.

►Lake effect in DuluthLake effect in Duluth is an example is an example of changes in temperature due to of changes in temperature due to being close to a large body of water.being close to a large body of water.

5. Altitude / Elevation5. Altitude / Elevation

►Temperature decreases as elevation Temperature decreases as elevation increases.increases.

less mass, less less mass, less

pressure, less pressure, less

absorptionabsorption

Exception:Exception: temperature inversion temperature inversion

►Conditions favorable for a Conditions favorable for a temperature inversion:temperature inversion:

cool, clear, calm nightcool, clear, calm night