1. Air Temperature

2. ► Temperature :  a measure of the average speed at which molecules are moving or vibrating.

3. ► Air temperature  the rate of motion of gas molecules in the atmosphere as a result of the absorption of energy  measured by a thermometer

4. Temperature scales ► Celsius  water freezes at 0 o  water boils at 100 o ► Fahrenheit  water freezes at 32 o  water boils at 212 o ► Kelvin  no molecular motion at 0 K  water freezes at 273 K  water boils at 373 K

5. Conversions ► o F = (1.8 x o C) + 32 ► o C = 0.56 ( o F - 32) ► K = o C + 273

6. 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

7. 1. Insolation A. Changing angle of noon sun throughout the year changes temperature on a seasonal basis.

10. ► Why temperature difference between equinoxes?

11. ► Spring : at end of cold, short day period  more energy loss ► Autumn : at end of warm, long day period  more energy gain

12. 1. Insolation B. Changing angle of sun throughout the day changes temperature on a daily basis.

15. ► lag between max insolation and max temperature  because highest temp at time of max ABSORBED insolation

16. 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

17. 3. Urban/rural Surface ► Evapotranspiration differences ► Urban impervious surfaces ► Urban highly absorbent (low albedo) surfaces ► Urban fuel consumption and excess heat ► “Urban heat island”

18. 4. Coastal vs. interior locations ► Water bodies have a moderating effect on temperature.

20. ► “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.

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

25. 5. Altitude / Elevation ► Temperature decreases as elevation increases.  less mass, less pressure, less absorption

27. Exception: temperature inversion

28. ► Conditions favorable for a temperature inversion:  cool, clear, calm night