章节大纲

  • 常规

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  • 大气压力

    Map showing storm reports including tornado, wind, and hail incidents in the southeastern US.

    What do storm reports reveal?
    ::暴风雨报告显示什么?

    The pressure in the atmosphere is an important factor in determining what the weather will be like. If the barometric pressure is high in an area, this will cause air to move to a region of lower pressure. The greater the difference in pressure between the two areas, the stronger the winds will develop. Under certain conditions, the winds can produce a tornado (a violent rotating column of air that reaches from a thunderstorm down to the ground).
    ::大气中的压力是决定天气状况的重要因素。 如果一个区域中的气压高, 气压会让空气进入低压区域。 两个区域之间的压力差异越大, 风势就越强。 在某些情况下, 风可以产生龙卷风( 从雷暴到地面的剧烈旋转的空气柱 ) 。

    Atmospheric Pressure
    ::大气压力

    Atmospheric pressure is the pressure exerted by particles in Earth’s atmosphere as those particles collide with objects. A barometer is an instrument used to measure atmospheric pressure. A traditional mercury barometer consists of an evacuated tube immersed in a container of mercury. Air molecules push down on the surface of the mercury. Because the inside of the tube is a vacuum, the mercury rises inside the tube. The height to which the mercury rises is dependent on the external air pressure.
    ::大气压力是地球大气中微粒与物体相撞时产生的压力。气压计是用来测量大气压力的工具。传统的汞气压计包括一个从汞容器中浸入的排出管。空气分子向汞表面倾斜。由于管内是真空,汞在管内会上升。汞上升的高度取决于外部空气压力。

    Two barometers: a mercury barometer tube and a dial aneroid barometer for pressure measurement.

    (A) A barometer measures atmospheric pressure as the height of a column of mercury. (B) A modern aneroid barometer in the form of a dial is used by meteorologists to help them predict upcoming weather.
    :伤心A) 气压计测量一列汞的高度时的大气压力。 (B) 气象学家使用一个拨号形式的现代无机气压计来帮助他们预测即将到来的天气。

    A more convenient barometer, called an aneroid barometer , measures pressure by the expansion and contraction of a small spring within an evacuated metal capsule.
    ::一种更方便的气压计,称为无固醇气压计,用来测量疏散金属胶囊内小泉的膨胀和收缩所造成的压力。

    Atmospheric Pressure and Altitude
    ::大气压力和高度

    At sea level, a mercury column will rise a distance of 760 mm. This atmospheric pressure is reported as 760 mmHg (millimeters of mercury). At higher altitudes, the atmospheric pressure is decreased and so the column of mercury will not rise as high. On the summit of Mt. Everest (elevation of 8848 m), the air pressure is 253 mmHg. Atmospheric pressure is slightly dependent on weather conditions. From the graph we can see the decrease in atmospheric pressure as the altitude increases. At sea level, the atmospheric pressure would be a little over 100 kPa (one atmosphere or 760 mm Hg). If we climb to the top of Mount Everest (the highest mountain in the world at 29,029 feet or 8848 meters), the atmospheric pressure will drop to slightly over 30 kPa (about 0.30 atmospheres or 228 mm Hg). This marked decrease in atmospheric pressure results in much lower levels of oxygen. Teams that climb this mountain must bring supplies of oxygen with them in order to breathe at these high altitudes.
    ::在海平面上,汞柱将上升760毫米的距离。这种大气压力报告为760毫米汞(毫米汞),在较高高度,大气压力将下降,因此汞柱不会上升。在珠穆朗玛峰峰顶峰(高度为8848米),空气压力为253毫米Hg。大气压力略有取决于天气条件。从图表中可以看出大气压力随着高度升高而下降。在海平面上,大气压力将略高于100千帕(一个大气或760毫米汞)。如果我们爬到珠穆朗玛峰顶端(世界最高山,29,029英尺或8848米),大气压力将略降至30千帕(约0.30层大气或228毫米汞),大气压力的明显下降导致氧气含量降低得多。攀登山的团队必须带氧气来呼吸这些高空。

    Graph showing the relationship between atmospheric pressure and altitude, indicating pressure decrease with height.

    Effect of altitude on atmospheric pressure.
    ::高度对大气压力的影响。

     

     Ever try cooking at the top of a mountain or at sea level? Compare how atmospheric pressure, and boiling point relate in this simulation: 
    ::曾经尝试过在山顶或海平面做饭吗? 比较这个模拟中大气压力和沸点的关联性:

    Summary
    ::摘要

    • Atmospheric pressure is the pressure exerted by gas particles in Earth’s atmosphere as those particles collide with objects.
      ::大气压力是地球大气中气体粒子造成的压力,因为这些粒子与物体相撞。
    • A barometer measures atmospheric pressure.
      ::气压计测量大气压力。
    • Atmospheric pressure decreases as the altitude increases.
      ::随着高度升高,大气压力下降。

    Review
    ::回顾

    1. Define atmospheric pressure.
      ::界定大气压力。
    2. What is an aneroid barometer?
      ::什么是无机气压计?
    3. How does the atmospheric pressure change as the altitude increases?
      ::随着高度升高,大气压力如何变化?