章节大纲

  • 常规

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  • 降水

    Scenes showing rain-soaked streets with flooding and a rainbow over palm trees.
     

    Want to stay dry? Don't go to these places!
    ::想保持干燥吗?

    The wettest locations in the world are in Mawsynram and Cherrapunji in India.  Monsoon  rains result in more than 460" of  rain  annually. The wettest place in the United States with 404" on average is on Maui (Big Bog). The wettest place in the continental United States is Langlois, Oregon with a mere 122" per  year .
    ::世界上最湿的地方是印度的Mawsynram和Cherrapunji。 季风降雨每年导致460多场降雨。 美国平均湿点为404场,在毛伊(大博格)上。 美国大陆最湿的地方是俄勒冈州兰洛伊斯(Langlois ) , 每年只有122场。

    Precipitation
    ::降降

     are needed for precipitation.  Precipitation  is  water  that falls from the sky. This may fall as liquid water, mostly as  rain . It may fall also as frozen water, such as  snow .
    ::降水需要降水。降水是指从天上掉下来的水。降水可能像液态水一样滴落,大多是雨水。降水也可能像雪等冰冻水一样滴落。

    Why Precipitation Falls
    ::为何降水瀑布

    Millions of water molecules in a cloud must condense to make a single raindrop or snowflake. The drop or flake falls when it becomes too heavy for updrafts to keep it aloft. As a drop or flake falls, it may collect more water and get larger.
    ::云层中的数百万水分子必须凝结, 才能产生一滴雨或雪花。 当云层变大时, 云层中的水分子会掉落, 其体积会变得太重, 无法保持升降。 当云层落下时, 它会收集更多的水, 并变大 。

    Types of Precipitation
    ::降水类型

    Why does it snow instead of rain? Air   determines which type of precipitation falls. Rain falls if the air temperature is above freezing (0° C or 32° F). Frozen precipitation falls if the air or ground is below freezing. Frozen precipitation may fall as  snow ,  sleet , or  freezing rain . Below, you can see how the different types form ( Figure   ).
    ::为何降雪而不是降雨?空气决定降水的种类。如果空气温度高于冰(摄氏0度或32度/摄氏度),雨就会降下。如果空气或地面低于冰,冰冻的降水就会降下。冰冻的降水会像雪、冰水或冻雨一样降下。下面,您可以看到不同种类的降水方式(图 ) 。

    Explanation of types of frozen precipitation: snow, sleet, freezing rain, and hail.
     
    Frozen precipitation may fall as snow, sleet, or freezing rain.

    Summary
    ::摘要

    • Precipitation falls when it gets too heavy to stay in a cloud.
      ::当降水变得太重 无法停留在云中时 降水就会下降
    • Rain droplets caught up in air currents within a cloud get larger by the addition of condensed droplets until they are too heavy and they fall.
      ::云层中空气流中积浮的雨滴随着凝结的滴子的增加而变大,直到它们过重而坠落。
    • If the ground is very cold, rain can freeze to become sleet or glaze.
      ::如果地面非常寒冷,雨会冻得流水或发泡。

    Review
    ::回顾

    1. Why do raindrops form and fall to the ground?
      ::为什么雨滴会形成 落到地上?
    1. Why does hail only come from cumulonimbus clouds?
      ::为什么冰雹只来自云层?
    1. How does sleet form?
      ::流水是怎样形成的?

    Explore More
    ::探索更多

    Use the resource below to answer the questions that follow.
    ::利用以下资源回答以下问题。

     

     

    1. What is precipitation?
      ::什么是降水?
    1. What is the most common form of precipitation?
      ::最常见的降水形式是什么?
    1. What is hail?
      ::什么是冰雹?
    1. What is sleet?
      ::什么是潜水?
    1. What is snow?
      ::什么是雪?