Page 312 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

276 part II The Water, Weather, and Climate Systems
extent to the drier southeastern part of the island. Mountain Hemlock and Coastal Mountain-heather alpine ecozones are restricted to the interior.
Two principal factors interact to de- termine Vancouver Island’s local climate zones. First is its maritime location be- tween latitudes 48°17′ N and 50°52′ N, in the westerlies wind belt. This means it is dominated by moist air masses com- ing from the Pacific Ocean, leading to high precipitation on the west coast.
The second factor is topography. Moist air masses are forced to rise oro- graphically over the Vancouver Island ranges, which occupy most of the is- land. Golden Hinde is the highest peak at 2201 m. The nature of the topography affects the patterns of the ecozones. as
elevation increases and air temperature decreases, Coastal Western Hemlock transitions into Mountain Hemlock, which in turn transitions into Coastal Mountain- heather alpine at the highest elevations. Orographic effects contribute to higher precipitation amounts on the windward side of the island, and to lower amounts in the rain shadow on the leeward side.
There is much less variation in tem- perature on Vancouver Island than in precipitation at the stations listed in Table GN 10.1. all are near sea level, which highlights contrasts in precipita- tion without elevation effects, and in the corresponding distribution of ecozones. The similarity in temperature regimes is a reflection of regional controls of climatic factors. But again, the pattern of ecozones
emphasizes that there is variability in tem- peratures across the island that is closely linked to increases in elevation. With this closer look at spatial variations in climate in mind, we shift our perspective to exam- ine climate categories across the globe.
geosystems now online Go to Chapter 10 on the MasteringGeography website (www.masteringgeography.com) for resources and activities. another exam- ple of climatic variation over a small region is New Zealand, whose North and South islands alone can be classified into more than eight climate zones. For a closer look, go to www.niwa.co.nz/education- and-training/schools/resources/climate/ overview.
The climate where you live may be humid with dis- tinct seasons, or dry with consistent warmth, or moist and cool—almost any combination is pos- sible. Some places have rainfall totaling more than 20 cm each month, with monthly average temperatures remain- ing above 27°C year-round. Other places may be rainless for a decade at a time. A climate may have temperatures that average above freezing every month, yet still threaten severe frost problems for agriculture. Students reading Geosystems in Singapore experience precipitation every month, totaling 228.1 cm during an average year, whereas students at the university in Karachi, Pakistan, measure only 20.4 cm of annual rainfall.
Climate is the collective pattern of weather over many years. As we have seen, Earth experiences an almost infi- nite variety of weather at any given time and place. But, if we consider a longer time scale, and the variability and extremes of weather over such a time scale, a pat- tern emerges that constitutes climate. For a given region, this pattern is dynamic rather than static; that is, climate changes over time (discussed in Chapter 11).
Climatology is the study of climate and its vari- ability, including long-term weather patterns over time and space and the controls that produce Earth’s diverse climatic conditions. No two places on Earth’s surface experience exactly the same climatic conditions; in fact, Earth is a vast collection of microclimates. How- ever, broad similarities among local climates permit their grouping into climatic regions, which are areas with similarity in weather statistics. As you will see in Chapter 11, the climate designations we study in this chapter are shifting as temperatures rise over the globe.
In this chapter: Many of the physical systems studied in the first nine chapters of this text interact to explain climates. Here we survey the patterns of climate using a series of sample cities and towns. Geosystems uses a simplified classification system based on physical fac- tors that help answer the question “Why are climates in
certain locations?” Though imperfect, this method is eas- ily understood and is based on a widely used classifica- tion system devised by climatologist Wladimir Köppen.
Review of Earth’s Climate System
Several important components of the energy–atmosphere system work together to determine climatic conditions on Earth. Simply combining the two principal climatic components—temperature and precipitation—reveals general climate types, sometimes called climate regimes, such as tropical deserts (hot and dry), polar ice sheets (cold and dry), and equatorial rain forests (hot and wet).
Figure 10.1 depicts the worldwide distribution of precipitation. These patterns reflect the interplay of numerous factors that should now be familiar to you, including temperature and pressure distributions; air mass types; convergent, convectional, orographic, and frontal lifting mechanisms; and the general energy avail- ability that decreases toward the poles. Corresponding maps illustrating global temperature patterns are found in Chapter 5. The principal components of Earth’s cli- mate system are summarized in the Geosystems in Action feature on pages 278–279.
Classifying Earth’s Climates
Classification is the ordering or grouping of data or phe- nomena into categories of varying generality. Such gen- eralizations are important organizational tools in science and are especially useful for the spatial analysis of cli- matic regions. Observed patterns confined to specific re- gions are at the core of climate classification. When using classifications, we must remember that the boundaries