Köppen’s climatic types are still considered validtoday. His climatic zones, like others, are by no meansstatic. Climatic zones shift with long-range weatherpatterns. The most noticeable shifts in these climaticzones have been observed over the northern portions ofNorth America and Asia and over Africa. Russia andCanada, for example, have been able to conductfarming at higher latitudes over the past 200 years dueto milder temperatures. Recent studies, however,indicate a general return of cooler temperatures at highlatitudes, and now the growing region is graduallymoving southward again where temperatures are moremoderate. In Africa, desert regions have made notableshifts southward due to decreasing precipitation.Trewartha is the most recent classifier of climate.Initially, his climatic classifications were based onKöppen’s; however, over the years, he has madesignificantchangesandisnowrecognizedfordeveloping his own six climatic groups. These sixgroups are tropical, dry, subtropical, temperate, boreal,and polar. Five of these groups are based ontemperature and one is based on precipitation (seeTable 6-2). Trewartha’s climatic groups, like Köppen’s,are also further broken down into climatic types andsubtypes.REVIEW QUESTIONSQ6-9. List the five climatic belts and theirboundaries.Q6-10. Name the three classifications of climatictypes.Q6-11. What are the five climatic types according toKöppen?CLIMATIC CONTROLSLEARNINGOBJECTIVE:Identifythecontrolling factors that affect climate.The variation of climatic elements from place toplace and from season to season is due to several factorscalled climatic controls. The same basic factors thatcause weather in the atmosphere also determine the6-7NORTH POLAR ZONENORTH TEMPERATE ZONESOUTH TEMPERATE ZONEHOT BELTSOUTH POLAR ZONE60402002040180 160 140 120 100 80 60 40 20 0 20 40 60 80 100 12050F ISOTHERM(WARMEST MONTH)MEAN ANNUALISOTHERM OF 68 FMEAN ANNUALISOTHERM OF 68 F50 F ISOTHERM(WARMEST MONTH)AGf06001Figure 6-1.—Temperature zones.
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