1. Temperature and Its Variation

2. Earth’s Rotation Remember we live on a rotating sphere
Direction of rotation:
From above North Pole, counterclockwise
From a distance, with North Pole at top, left to right

3. Effects of Earth’s Rotation
3 main effects:
Axis and equator basis of geographic grid
A day is a convenient measure of time passing
Diurnal, or daily, rhythm in daylight, air temp, etc.
Surface processes all respond to diurnal rhythm
Coriolis force due to Earth’s rotation
How fast are you moving at the Equator?
At the Poles?

4. Earth’s Revolution around Sun
days / orbit → Feb 29th every 4th year
Counterclockwise motion from above
Elliptical orbit: There is a 6% difference in insolation between Perihelion and Aphelion.
Perihelion
Closest to Sun
Jan. 3rd
Aphelion
Farthest from Sun
July 4th

5. World Latitude Zones Terms used for latitude zones
Generally greater seasonal change with greater distance from Equator

10. Solar Heating of Land & Water
Surface layer of large body of water heats & cools more slowly than land
This difference shows up in temp patterns
e.g. diurnal temp pattern, maritime vs. continental
San Francisco
(Maritime)
Yuma
(Continental)

13. Thermal Properties of Water
4 factors make water heat & cool slower than land 1. 2.
Sun penetrates water
Heat capacity of water greater 3. 4.
Water mixes
More evaporation over water

14. 5 Factors Influencing Local Temps
Latitude – less insolation at higher latitudes
Surface type – urban land absorbs more heat
Coastal vs. Interior – less temp range at coast
Elevation – temps decrease with altitude
Greater annual temp range at high latitudes
Atmospheric & oceanic circulation- temp can vary greatly based on where air & sea water are coming from

15. Urban Heat Island Evapotranspiration helps keep rural areas cool
Urban asphalt & concrete has little evapotranspiration
Building & paving materials absorb more heat than natural surfaces
Automobiles, air conditioning & other machines make city warmer than surroundings

19. Daily Cycle of Radiation & Air Temp
Shortwave radiation from Sun greater than longwave radiation during daylight hours.
Energy surplus in daylight
Deficit in darkness
Temp usually highest in mid- afternoon, lowest just after sunrise

20. Maritime vs. Continental
Daily range of temp less at maritime location
North Head, WA much less range than El Paso, TX throughout the year

21. Annual Cycle of Air Temperature
Annual temperature range = max temp month – min temp month
2 most important factors:
Annual insolation (latitude)
Maritime or continental effect
Like daily temp cycle, maritime climates have less annual temp range than continental

24. Annual Cycle of Air Temperature
Winnipeg & Scilly Is. have identical insolation curves
Winnipeg much colder fall, winter, spring due to extreme continental location
Scilly Is. Reach max & min temps later Due to influence of water

25. World Temperature Patterns
Isotherm – line on map connecting all points with same temperature
January
Coldest in Siberia, northern Canada & Greenland
Warmest in southern Africa and interior Australia
Oceans warmer than land in northern hemisphere

26. World Temperature Patterns
Maritime influence warms in winter, cools in summer
July
Northern hemisphere continents have warmed dramatically since January
Aside from Antarctica, southern hemisphere not very cold in winter
Maritime influence

27. Annual Temperature Range
= warmest month mean temp – coldest month mean temp
Greatest temp ranges in Siberia & NW Canada
Continental locations
Smallest temp ranges in Equatorial oceans
Maritime influence

28. Wind-Chill Index “Feel” of temperature – based on: Actual temperature
Windspeed – higher means colder

29. Heat Index “Feel” of temperature on hot days, based on:
Actual temperature
Relative Humidity

30. Chapter Summary Earth’s rotation and orbit Air Temperature
Daily cycle of air temperature
Annual cycle of air temperature
Measurement of air temperature