章节大纲

  • 常规

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  • 气旋

    Weather systems showing clouds and a snowy landscape, illustrating cyclone impacts and conditions.
     

    What is the difference between a cyclone, a hurricane, and a typhoon?
    ::旋风、飓风和台风有什么区别?

    Sometimes, interactions between   and the   create a large, rotating  storm  system with a low pressure region at the center. If the  cyclone  forms over warm  water , it can pick up moisture and bring high  winds  and heavy rains when it makes landfall. This is called a   in the Atlantic Ocean and a typhoon in the Pacific.   are also rotating storms, but they are much smaller, and generally form over land.
    ::有时,在暴风雨之间和形成一个大型的、旋转的暴风系统,其中心是低压区域。如果气旋形成于暖水之上,它可以吸收水分,并在登陆时带来高风和大雨。这在大西洋和太平洋被称为台风,也是旋转的暴风雨,但规模要小得多,而且一般在陆地上形成。

    Mid-Latitude Cyclones
    ::中纬度旋风

    Cyclones can create the most intense storms on Earth. A  cyclone  is a system of winds that rotate around a low pressure center. The swirling air rises and cools. This creates   and  .  Cyclones that form in the tropics usually become a hurricane or a tropical storm.  Cyclones that form at higher latitudes are called extratropical, or mid-  cyclones.
    ::气旋可以制造地球上最强烈的风暴。气旋是一个围绕低压力中心旋转的风系统。 旋转的空气上升和冷却。 这产生和. 热带形成的气旋通常成为飓风或热带风暴。 在高纬度形成的气旋被称为热带气旋, 或中气旋。

    Mid-latitude cyclones  typically form at the  polar front . Two very different air masses blow past each other in opposite directions. The Coriolis effect causes winds to strike the polar front at an angle. Warm and cold   form next to each other.
    ::中纬度龙卷风通常形成于极端。 两种截然不同的气团向相反的方向相互吹过。 科里奥利斯效应使风从一个角度吹向极端。 温度和寒冷的形式彼此相邻。

    Most winter storms in the middle latitudes, including most of North America and Europe, are caused by mid-latitude cyclones ( Figure   ).
    ::中纬度地区,包括北美和欧洲大部分地区,大多数冬季风暴都是由中纬度旋风造成的(图)。

    Map illustrating a mid-latitude cyclone, showing wind directions, temperature fronts, and a low-pressure area.
     
    A hypothetical mid-latitude cyclone affecting the United Kingdom. The arrows point the wind direction and its relative temperature; L is the low pressure area. Notice the warm, cold, and occluded fronts.

    The warm air at the  cold front  rises and creates a low pressure cell. Winds rush into the low pressure. This creates a rising  column  of air. The air twists, rotating counterclockwise in the  Northern Hemisphere  and clockwise in the  Southern Hemisphere . Since the rising air is moist,  rain  or  snow  falls.
    ::寒冷前方的温暖空气升起并形成低压电池。 风向低压, 形成一列上升的空气。 气旋, 北半球的逆时针旋转, 南半球的顺时针旋转。 由于上升的空气是湿的, 雨或雪会降下来 。

    Mid-latitude cyclones generally move eastward with the westerly winds. These two- to five- day  storms can reach 1,000 to 2,500 km (625 to 1,600 miles) in diameter. They can produce winds up to 125 km (75 miles) per hour.
    ::中纬度龙卷风一般随西风向东移动,两至五天的风暴直径可达1 000至2 500公里(625至1 600英里),风速可达每小时125公里(75英里)。

    Nor'easters
    ::东北人

    Mid-latitude cyclones are especially fierce in the mid-Atlantic and New England states. They are called  nor’easters  because they come from the northeast. About 20-40 nor’easters form each  year , but only a few are severe ( Figure   ).
    ::中大西洋和新英格兰各州的中纬度龙卷风特别猛烈。 它们被称为“不为人知 ” , 因为它们来自东北部。 每年约有20-40个,也有一些,但只有少数是严重的(图 ) 。

    Satellite image showing a mid-latitude cyclone with distinct temperature gradients.
     
    The 1993 “Storm of the Century” was a nor’easter that covered the entire eastern seaboard of the United States.

     

    Summary
    ::摘要

    • A cyclone is a system of winds rotating around an area of low pressure.
      ::旋风是一种围绕低压地区旋转的风系统。
    • A mid-latitude cyclone forms at the polar front. This occurs when the temperature difference between air masses is very large.
      ::在极端形成中纬度气旋。当空气质量之间的温度差异很大时,就会发生这种情况。
    • Nor'easters are mid-latitude cyclones that come from the northeast.
      ::东北的中纬度龙卷风 也是来自东北的中纬度龙卷风

    Review
    ::回顾

    1. What is a cyclone?
      ::什么是旋风?
    1. What are the motions of air in a mid-latitude cyclone?
      ::中纬度气旋的空气运动是什么?
    1. What is a nor'easter?
      ::什么是"不伦瑞克"?