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3.2.6 Surface Properties of the Earth This section describes the surface properties of the earth and their reflectivity or albedo. water
ALBEDO: INTRODUCTION TO SURFACES
Ice and clean snow surfaces have high albedos. Sea Ice in Lancaster Sound in the Canadian Arctic. Differences in surface characteristics affect the amount of radiation reflected from Earth’s surface back to space. Ice and clean snow surfaces have high albedos. A large percentage of solar radiation (light and heat) is reflected. The greater the area covered by continental ice sheets, the cooler the planet. Oceans and plants have low albedo and absorb most of radiation striking them. Increases in areas of ocean and vegetation lead to decrease in planetary albedo and a warmer Earth. Any surface receiving the suns ray’s will absorb some of the energy and reflect the rest. Some interesting effects of and consequences for land use are shown below. See sections on ecosystems.
Source: Science and Impacts of Climate Change CD -Presentation Graphics (2002) MSC Environment Canada/ ESS Natural Resources Canada, December
ACTIVITY 1 1. On a warm day put thermometers – for the same length of time – on three cars whose colors range from light to medium to dark. Record the temperatures. Repeat three tiimes for each color. What is being measured ? Why are there differences in the readings? What cost is saved by driving a light coloured car? How is this knowledge useful in choosing clothing? 2. Repeat the experiment by placing thermometers on natural vegetation, bare soil, concrete sidewalk, and asphalt. Explain these results based on the light and heat energy. URBAN HEAT ISLAND Below is a sketch of an Urban Heat-Island Profile. Notice that this is graph is presented in Fahrenheit for late afternoon temperatures. 1 Celsius degree = 1.8 Fahrenheit degrees plus 32) are highest in the downtown core, whereas the outer peripheries (rural areas) have lower temperatures.
- What is the range of temperature shown between the downtown core and the outer peripheries (rural areas) in Fahrenheit degrees? In Celsius degrees?
- List 5 reasons why the downtown or urban core is warmer than the suburbs.
- Why would the late afternoon be the best time to graph temperatures?
- How would this phenomenon affect gardeners? Parks and Recreation departments?
The warming of urban air increases in intensity and area as cities grow. This tends to increase the risk of more frequent heat waves. These heat waves occasionally cause death, particularly among elderly people, very young people and those who are ill in health. During rainy seasons, this “heat island” increases the intensity and frequency of rain showers, which creates a higher risk of flooding or mudslides.
ACTIVTY 3 -Research
- Find examples of heat waves in Toronto or Chicago where deaths due to heat wave have been documented. What are the two basic reasons people die at this time?
- Jane Jacob’s “Dark Times Ahead” cites sociological studies that add an other major reason for these deaths. What was discovered to be this additional factor
a) What is the range of albedos found in this diagram?
b) Which surface absorbs the most heat? The least? Why is there a trend to “green roofs” HINT 7.4.??? Which purchases should be influenced by this diagram that are not labelled with albedo or reflectivity ratings?
ACTIVTY 5- Research
At what concentration of urban development or population does the urban heat island effect begin?