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  3. A weather map is an important tool for geographers. A succession of three or four maps presents a continuous picture of weather

A weather map is an important tool for geographers. A succession of three or four maps presents a continuous picture of weather

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问题    A weather map is an important tool for geographers. A succession of three or four maps presents a continuous picture of weather changes. Weather forecasters are able to determine the speed of air masses and fronts; to determine whether an individual pressure area is deepening or becoming shallow and whether a front is increasing or decreasing in intensity~ They are also able to determine whether an air mass is retaining its original characteristics or taking on those of the surface over which it is moving. Thus, a most significant function of the map is to reveal a synoptic picture of conditions in the atmosphere at a given time.
   All students of geography should be able to interpret a weather map accurately. Weather maps contain an enormous amount of information about weather conditions existing at the time of observation over a large geographical area. They reveal in a few minutes what otherwise would take hours to describe. The United States Weather Bureau issues information about approaching storms, floods, fronts and all climatic conditions in general. Twice a month it issues a 30-day "outlook" which is a rough guide to weather conditions likely to occur over broad areas of the United States. These 30-day outlooks are based upon an analysis of the upper air levels which often set the stage for the development of air masses, fronts, and storms.
   Considerable effort is being exerted today to achieve more accurate weather predictions. With the use of electronic instruments and earth satellites, enormous gains have taken place recently in identifying and tracking storms over regions which have but few meteorological stations. Extensive experiments are also in progress for weather modification studies. But the limitations of weather modification have prevented meteorological results except in the seeding of super-cooled, upslope mountainous winds which have produced additional orographic precipitation on the windward side of mountain ranges. Nevertheless they have provided a clearer understanding of the fundamentals of weather elements.
The observation of weather conditions by satellites is advantageous because it ______.
选项 A、enables man to alter the weather
B、makes weather prediction easier
C、gives the scientific information not obtained readily otherwise
D、uses electronic instruments
答案C
解析 由题干satellites可定位到第三段的第二句话With the use…meteorological stations．(借助电子仪器和人造卫星，在那些只有极少数气象站的地区人们在辨别和追踪的风暴等天气状况方面最近有巨大的进展)，也就是说有了电子仪器和人造卫星，没有气象站也照样能获得气象信息，因此选[C] 。有了气象卫星，天气预报更准确，但并不意味着人类能改变天气，或使天气预报更容易，所以排除[A] 和[B] ；电子仪器与人造卫星是并列的关系，而不是因果关系，所以排除[D] 。
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