Page 151 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

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Chapter 4 atmosphere and Surface Energy Balances 115
polar deficits drives a vast global circulation of both en- ergy and mass. Average monthly net radiation at the top of the atmosphere varies seasonally, highest in the north- ern hemisphere during the June solstice and highest in the southern atmosphere during the December solstice.
Surface energy measurements are used as an analyt- ical tool of microclimatology. Net radiation (NET R) is the value reached by adding and subtracting the energy inputs and outputs at some location on the surface; it is the sum of all shortwave (SW) and longwave (LW) radia- tion gains and losses. Average annual net radiation var- ies over Earth’s surface and is highest at lower latitudes. Net radiation is the energy available to do the “work” of running the global climate system, by melting ice, rais- ing temperatures in the atmosphere, and evaporating water from the oceans.
microclimatology (p. 104)
net radiation (NET R) (p. 105)
11. Sketch a simple energy-balance diagram for the tro- posphere. Label each shortwave and longwave com- ponent and the directional aspects of related flows.
12. Intermsofsurfaceenergybalance,explainthenetradi- ation (NET R) and its general pattern on a global scale.
■ Plot typical daily radiation and temperature curves for Earth’s surface—including the daily temperature lag.
Air temperature responds to seasons and variations in insolation input. Within a 24-hour day, air temperature peaks between 3:00 and 4:00 p.m. and dips to its lowest point right at or slightly after sunrise. Air temperature lags behind each day’s peak insolation. The warmest time of day occurs not at the moment of maximum inso- lation but at the moment when a maximum of insolation is absorbed.
13. Why is there a temperature lag between the highest Sun altitude and the warmest time of day? Relate your answer to the insolation and temperature pat- terns during the day.
14. What are the nonradiative processes for the expendi- ture of surface net radiation on a daily basis?
15. Compare the daily surface energy balances of
El Mirage, California, and Pitt Meadows, British Columbia. Explain the differences.
■ List typical urban heat island conditions and their causes, and contrast the microclimatology of urban areas with that of surrounding rural environments.
A growing percentage of Earth’s people live in cities and experience a unique set of altered microclimatic effects: increased conduction by urban surfaces, lower albedos, higher NET R values, increased water runoff, complex radiation and reflection patterns, anthropogenic heating, and the gases, dusts, and aerosols of urban pollution. All of these combine to produce an urban heat island (UHI). Air pollution, including gases and aerosols, is greater in urban areas, producing a dust dome that adds to the urban heat island effects.
urban heat island (UHI) (p. 107) dust dome (p. 109)
16. What observations form the basis for the urban heat island concept? Describe the climatic effects attributable to urban as compared with nonurban environments.
17. Which of the items in Table 4.1 have you yourself experienced? Explain.
18. Assess the potential for solar energy applications in our society. What are some negatives? What are some positives?