Answer to Question 1
ANSWER: Dfa climates are humid continental with hot summers, while Dfb climates are humid continental with long cool summers. Both Des Moines, Iowa, and Winnipeg, Canada, experience a large annual temperature range. This is characteristic of climates located in the northern interior of continents. In fact, as we move poleward, the annual temperature range increases. In Des Moines, the annual temperature is 31C (56F), while 950 km (590 mi) to the north in Winnipeg, annual temperature is 38C (68F). Most of the summer rain is in the form of convective showers, although an occasional weak frontal system can produce more widespread precipitation, as can a cluster of thunderstormsthe mesoscale convective complex. The weather in both climatic types can be quite changeable, especially in winter, when a brief warm spell is replaced by blustery winds and temperatures plummeting well below -30C (-22F).
Answer to Question 2
ANSWER: Moving equatorward of marine climates, the influence of subtropical highs becomes greater, and the summer dry period more pronounced. Gradually, the climate changes from marine to one of dry-summer subtropical (Cs), which is also called Mediterranean. Along the west coast of North America, Portland, Oregonbecause it has rather dry summersmarks the transition between the marine climate and the dry-summer subtropical climate to the south.
Oceanic circulation, which is driven mainly by the prevailing winds, moderates earth's climate.
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