单选题 A weather map is an important tool for geographers. A succession of three of four maps presents a continuous picture of weather changes. Weather forecasts 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, frosts, droughts, 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 with 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 orographical precipitation on the windward side of mountain ranges. Nevertheless, they have provided a clearer understanding of the fundamentals of weather elements.
单选题 One characteristic of weather maps not mentioned by the author in this passage is ______.
  • A. wind speed
  • B. thermal changes
  • C. fronts
  • D. barometric pressure
【正确答案】 B
【答案解析】本文在第一段第二句中列举了从气象图上可以确定的信息，其中“the speed of air masses”即A选项，“fronts”即C选项，“whether an individual pressure area”即D选项，惟有B所包含的信息不在列举之列，所以此题的正确答案应当为B。
单选题 The thirty-day forecast is determined by examining ______.
  • A. upper air levels
  • B. satellite reports
  • C. changing fronts
  • D. daily air maps
【正确答案】 A
【答案解析】本文第二段最后一句明确指出“These 30-day outlooks are base upon an analysis of the upper air levels with often set the stage for the development of air masses，fronts， and storms”，所以本题的正确答案应当为A。
单选题 The observation of weather conditions by satellites is advantageous because it ______.
  • A. gives the scientist information not obtained readily otherwise
  • B. enables man to alter the weather
  • C. uses electronic instruments
  • D. is modern
【正确答案】 D
【答案解析】本文第二段第二句提到运用卫星，科学家可以对只有很少气象站的地区的气象进行分析、判断，这与答案D意思相近，所以本题正确答案应当为D。
单选题 A weather map is synoptic because it ______.
  • A. summarizes a great deal of information
  • B. can be interpreted accurately
  • C. appears daily
  • D. shows changing fronts
【正确答案】 A
【答案解析】由第一段最后一句中的“thus”可推知，此句中的“synoptic picture of conditions”是前面几句中提到的天象图各种信息作用的综合，所以A的意思最准确。
单选题 At the present time, experiments are being conducted in ______.
  • A. 30-day "outlook"
  • B. controlling storms
  • C. satellites
  • D. manipulating weather
【正确答案】 D
【答案解析】文中第三段第三句说“在改造天气的研究中人们进行了许多实验”，D项与此意相符，所以选项D为正确答案。