Page 147 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

Chapter 4 atmosphere and Surface Energy Balances 111
East River
Con Edison
(a) Rooftops in Queens, New York, in September 2011.
100
80
60
40
20
0
(b) Graph shows the higher temperature of black roofs as compared to bright white or green (vegetated) roofs.
▲ Figure 4.18 Effects of rooftop materials on urban heat islands. [(a) naSa. (b) Columbia University and naSa Goddard institute for Space Studies.]
City planners and architects use a number of strat- egies to mitigate UHI effects, including planting of veg- etation in parks and open space (urban forests), “green” roofs (rooftop gardens), “cool” roofs (high-albedo roofs), and “cool” pavements (lighter-coloured materials such as concrete, or lighter surface coatings for asphalt). The City of Toronto was the first in North America to pass a bylaw requiring the construction of green roofs on new development. The bylaw has applied to new residen- tial, commercial, and institutional building permit ap- plications since January 31, 2010, and to new industrial development since April 30, 2012. In addition to lower- ing urban outdoor temperatures, such strategies keep buildings’ interiors cooler, thereby reducing energy con- sumption and greenhouse gases caused by fossil-fuel emissions (see the chapter-opening photo of the living
roof on Toronto’s Robertson Building). During the hot- test day of the 2011 New York City summer, temperature measurements for a white roof covering were 24 C° cooler than for a traditional black roof nearby (Figure 4.18). Other studies have shown that for structures with solar panel arrays, the roof temperatures under the shade of the panels dropped dramatically.
With predictions that 60% of the global population will live in cities by the year 2030, and with air and water temperatures rising because of climate change, UHI issues are emerging as a significant concern both for physical geographers and for the public at large. Studies have found a direct correlation between peaks in UHI intensity and heat-related illness and fatalities. More information is available from Health Canada and the U.S. Environmental Protection Agency, including mitigation strategies, publications, and hot-topic discus- sions, at www.hc-sc.gc.ca/ewh-semt/pubs/climat/actue_care- soins_actifs/index-eng.php.
Black roof Green roof White roof Air temperature
August 1 2 3 4 5
CrITICAlthinking 4.3
Looking at your Surface Energy Budget
Given what you now know about reflection, absorption, and net radiation expenditures, assess your wardrobe (fabrics and colours); house, apartment, or dorm (colours of exterior walls, especially south- and west-facing, or in the Southern Hemisphere, north- and west-facing); roof (orientation relative to the Sun and roof colour); automo- bile (colour, use of sun shades); bicycle seat (colour); and other aspects of your environment to improve your per- sonal energy budget. are you using colours and materi- als to save energy and enhance your personal comfort? Do you save money as a result of any of these strategies? What grade do you give yourself? in Chapter 1, you as- sessed your carbon footprint. How does that relate to these energy-budget considerations (orientation, shade, colour, form of transportation)? •
The Earth and The Human Denominator feature sum- marizes some key interactions between humans and the Earth–atmosphere energy balance. The effects of human activities on Earth’s energy balance are driving changes in all Earth systems.
Georeport 4.3 Phoenix Leads in Urban Heat Island Research
in Phoenix, arizona, a team of scientists, architects, and urban planners are studying urban climate elements—wind movement, building arrangement, street-level shading effects, and the incorporation of vegetation and water features
into urban planning. in 2008, the team (sponsored by arizona State University, in partnership with the national Weather Service and key stakeholders such as private energy firms and the city government) launched a sustainable urban development plan aimed at UHi mitigation and pedestrian comfort. One strategy for moderating regional climate change is to plant a double row of broad-canopy, low-water-demand trees to increase shading along streets, in conjunction with low shrubs to reduce pedestrian exposure to longwave radiation emitted from asphalt roads.
Temperature (°C)