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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.