1. 17.3 Local temperature variations
Objectives
Identify the factors that cause the intensity of insolation to vary from place to place.
Describe how the characteristics of a material affect its rate of solar absorption.
Answer questions about a temperature map.

2. Local Temperature Variations
Insolation heats Earth’s surface and atmosphere unequally
Varies with the time of day, latitude, and time of year
Characteristics of a material affect both how much insolation is absorbed and how the absorbed energy affects the temperature

3. Intensity of Insolation
Intensity depends on the angle at which the sun’s rays strike Earth’s surface
Directly overhead = maximum energy
Angle decreases (Energy of the rays is spread out over a larger area) = Energy per unit area decreases

4. Intensity of Insolation Cont’d
Sometimes sunlight must travel farther through the atmosphere
Travels farther through the atmosphere
Absorbed or reflected before it reaches Earth’s surface
Reduces amount of solar energy that reaches Earth’s surface

5. Time of Day Sun’s rays are closest to vertical at noon
Intensity of insolation is greatest
Warmest hour of the day is usually after noon
Lower atmosphere receives more heat from the ground than it loses

6. Latitude B/c Earth is spherical Near equator Near poles
Sun rays hit Earth at almost 90o angle year round
Hot climate
Near poles
Sun rays hit Earth at low angles
Cold year round
May have no sunlight for all or part of the year

7. Time of Year Locations in middle latitudes
Get near-vertical rays is the summer
Summers are hot
Hottest day is after the most direct rays hit Earth for the longest period of time
Earth’s surface absorbs heat
Get less vertical rays in the winter
Winters are cold

8. Cloud Cover
Intensity of the insolation that reaches Earth’s surface also depends on how much energy makes it through the atmosphere w/o being absorbed, reflected, or scattered back to space

9. Cloud Cover Cont’d
More solar energy reaches Earth’s surface on clear day
More radiation travels from Earth’s surface into space on clear nights

10. Heating of Water and Land
Continents are warmer than nearby ocean waters in summer and colder in winter

11. Heating of Water and Land Cont’d
Reasons why water warms slower
Heat energy from insolation spreads through a greater depth in water than on land
Landonly the top few cm of soil
Waterdepth of many meters, spreads heat easily by convection b/c it is a fluid

12. Heating of Water and Land Cont’d
2) Some solar energy is used in the process of evaporation
Less solar energy is available to raise the temperature of the water

13. Heating of Water and Land Cont’d
Water needs more energy than land to raise its temperature
Specific heat: the amount of heat needed to raise 1 gm of a substance by 1oC
Almost 3x’s the specific heat of land
Higher the specific heat, the slower the temperature change

14. Heating of Water and Land Cont’d
Various types of land surfaces absorb heat differently
Dark/rough surfaces absorb more energy than light/smooth surfaces

15. Temperature Maps Color represent temperature on temperature maps
Isoterms: lines that connect places with the same temperature
Does not follow the lines of altitude

16. 17.3 Exit Ticket Answer the following questions.
Use complete sentences.
You may NOT use your book.
You MAY use your notes.
This is a quiz grade.
What are the factors that cause the intensity of insolation to vary from place to place?
How does the characteristics of a material affect its rate of solar absorption?
Explain how to use a temperature map.