Page 177 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

Looking for additional review and test prep materials? Visit the Study Area in MasteringGeographyTM to enhance your geographic literacy, spatial reasoning skills, and understanding of this chapter’s content by accessing a variety of resources, including interactive maps, geoscience animations, satellite loops, author notebooks, videos, RSS feeds, web links, self-study quizzes, and an eText version of Geosystems.
Chapter 5 Global Temperatures 141
or heat capacity, requiring far more energy to increase its temperature than does an equal volume of land.
Ocean currents and sea-surface temperatures also af- fect land temperature. An example of the effect of ocean currents is the Gulf Stream, which moves northward off the east coast of North America, carrying warm water far into the North Atlantic. As a result, the southern third of Iceland experiences much milder temperatures than would be expected for a latitude of 65° N, just below the Arctic Circle (66.5°).
Moderate temperature patterns occur in locations near water bodies, and more extreme temperatures occur inland. The marine effect, or maritime effect, usually seen along coastlines or on islands, is the moderating in- fluence of the ocean. In contrast, the continental effect occurs in areas that are less affected by the sea and there- fore experience a greater range between maximum and minimum temperatures on a daily and yearly basis.
land–water heating differences (p. 124) transparency (p. 125)
specific heat (p. 125)
Gulf Stream (p. 126)
marine effect (p. 126) continental effect (p. 126)
9. List the physical characteristics of land and water that produce their different responses to heating from absorption of insolation. What is the specific effect of transparency in a medium?
10. What is specific heat? Compare the specific heat of water and soil.
11. Describe the pattern of sea-surface temperatures (SSTs) as determined by satellite remote sensing. Where is the warmest ocean region on Earth?
12. What effect does sea-surface temperature have on air temperature? Describe the negative feedback mecha- nism created by higher sea-surface temperatures and evaporation rates.
13. Differentiate between temperatures at marine versus continental locations. Give an example of each from the text discussion.
■ Interpret the pattern of Earth’s temperatures from their portrayal on January and July temperature maps and on a map of annual temperature ranges.
Maps for January and July instead of the solstice months of December and June are used for temperature compari- son because of the natural lag that occurs between inso- lation received and maximum or minimum temperatures experienced. Each line on these temperature maps is an isotherm, an isoline that connects points of equal temper- ature. Isotherms portray temperature patterns.
Isotherms generally trend east–west, parallel to the equator, marking the general decrease in insolation and net radiation with distance from the equator. The thermal equator (isoline connecting all points of highest mean
temperature) trends southward in January and shifts north- ward with the high summer Sun in July. In January, it ex- tends farther south into the interior of South America and Africa, indicating higher temperatures over landmasses.
In the Northern Hemisphere in January, isotherms shift equatorward as cold air chills the continental inte- riors. The cold experienced at the coldest area on the map results from winter conditions of consistently clear, dry, calm air; small insolation input; and an inland location far from any moderating maritime effects.
isotherm (p. 130) thermal equator (p. 131)
14. What is the thermal equator? Describe its location in January and in July. Explain why it shifts position annually.
15. Observe trends in the pattern of isolines over North America as seen on the January average-temperature map compared with the July map. Why do the patterns shift?
16. Describe and explain the extreme temperature range experienced in north-central Siberia between January and July.
17. Where are the hottest places on Earth? Are they near the equator or elsewhere? Explain. Where is the coldest place on Earth?
18. Compare the maps in Figures 5.14 and 5.15:
(a) Describe what you find in central Greenland in January and July; (b) look at the south polar region and describe seasonal changes there. Characterise conditions along the Antarctic Peninsula in January and July (around 60° W longitude).
■ Discuss heat waves and the heat index as a measure of human heat response.
Global climate change is presenting challenges to people across Earth. Recent heat waves, prolonged periods of high temperatures lasting days or weeks, have caused fatalities and billions of dollars in economic losses. The humidex in- dicates the human body’s reaction to air temperature and water vapour. The level of humidity in the air affects our natural ability to cool through evaporation from skin.
heat wave (p. 136)
19. On a day when temperature reaches 37.8°C, how does a relative humidity reading of 50% affect apparent temperature?
20. Discuss recent heat waves in Australia and the United States. How do these events differ from previ- ous heat waves in these regions?
Answer to Critical Thinking 5.1: Vancouver exhibits marine effects on temperature because of the cooling waters of the Pacific Ocean. Winnipeg has a continental location and therefore a greater annual temperature range. Note that Winnipeg is also slightly higher in elevation, which has a small effect on daily temperature variations.