44 Seasons and Climate-Low

Seasons and Climate FOCUS Question How do seasons vary in different climate zones on Earth?

季节和气候焦点问题地球上不同气候带的季节是如何变化的?

Seeing the Seasons Imagine getting on an airplane in Panama City, Panama. The air is hot and steamy. After hours on the plane, you land in Anchorage, Alaska. Here, you see your breath in the frozen air, and snow flies all around you. Now imagine you are in Boston, Massachusetts, in July. It feels like Panama—hot and humid. But if you were in Boston in January, it would feel like chilly Alaska. Planet Earth has a huge variety of climates—the long-term weather conditions in an area. There are wet tropical forests and frozen Antarctic deserts. Some places have seasons that change dramatically throughout the year. Why does this happen?

想象你在巴拿马的巴拿马城坐飞机。 空气又热又湿。 在飞机上数小时后，你降落在阿拉斯加的安克雷奇。 在这里，你可以在冰冻的空气中看到自己的呼吸，雪在你周围飞舞。 现在想象你七月在马萨诸塞州的波士顿。 感觉就像巴拿马一样——又热又潮湿。 但如果你一月份在波士顿，感觉就像阿拉斯加一样寒冷。 地球上有各种各样的气候——一个地区的长期天气状况。 这里有潮湿的热带森林和冰冻的南极沙漠。 有些地方一年四季变化很大。 为什么会发生这种情况?

The Sun and the Seasons Earth has three major climate zones—large areas where the temperature and precipitation are similar. The coldest areas called the polar zones, are near the North and South Poles. The tropics lie near the equator. These zones are warm year-round. In between are the temperate zones, which can be both cold and hot. Climate zones are caused in part by Earth's round shape. At the poles, the Sun shines at a low angle over the curved surface. The rays scatter as they pass through more of the atmosphere. The light energy spreads out over a larger area of the surface, providing far less heat. This keeps the polar zones very cold. In the tropics, the Sun shines down on Earth's surface at a high angle. The light energy is much more focused, creating intense heat. This keeps the tropics warm year-round.

太阳与季节地球有三个主要的气候带——温度和降水相似的大片区域。 最冷的地区叫做极地，在南北极附近。 热带地区位于赤道附近。 这些地区全年温暖。 中间是温带，既冷又热。 气候带部分是由地球的圆形造成的。 在两极，太阳以较低的角度照射在弯曲的表面上。 当光线穿过更多的大气层时，它们会散射。 光能扩散到更大的表面区域，提供更少的热量。 这使得极地非常寒冷。 在热带地区，太阳以很高的角度照射在地球表面。 光能更加集中，产生强烈的热量。 这使得热带地区全年都很温暖。

You might think the temperate zones, between the hot tropics and cold poles, would be pleasantly mild year- round. But the temperate zones are more complicated. Earth is not vertical, or straight up and down, as it orbits the Sun. Its axis—the imaginary line from pole to pole— tilts to one side. As Earth orbits the Sun, each pole leans toward the Sun for half the year and away from the Sun for the other half. This causes Earth's seasons, as explained in the diagram below.

你可能认为位于热带和冷极之间的温带地区一年四季都温和宜人。 但温带地区的情况更为复杂。 地球不是垂直的，也不是垂直的，因为它围绕太阳运行。 它的轴——从极点到极点的假想线——向一边倾斜。 当地球围绕太阳公转时，每一极每年有半年时间朝向太阳，另一半时间远离太阳。 这导致了地球的季节，如下图所示。

Cold and Colder: Polar Zones Near Earth's North and South Poles, it is below freezing nearly year-round. Many areas are covered in permanent snow and ice. During summer in the Northern Hemisphere, the northern polar zone gets twenty-four hours of sunlight per day. The southern polar zone gets twenty-four hours of darkness. During summer in the Southern Hemisphere, the opposite is true. With all those hours of daylight, it seems as though the poles would have hot summers. But the Sun is always low to the horizon, and its rays spread out, never delivering much heat. The poles do experience seasons. During the brief, cool summer, some ice and snow melt. Plants sprout and animals have their young. As the long winter approaches, many animals store food, grow thick coats, or hibernate to survive.

在地球的南北两极附近，几乎全年都低于冰点。 许多地区被永久冰雪覆盖。 在北半球的夏季，北极地区每天有24小时的阳光。 南极地区有24小时的黑暗。 在南半球的夏季，情况正好相反。 有了这么长时间的白昼，两极似乎会有炎热的夏天。 但太阳总是在地平线以下，它的光线分散开来，从来没有传递太多的热量。 两极确实经历季节。 在短暂而凉爽的夏天，一些冰雪融化了。 植物发芽，动物产卵。 随着漫长的冬天的临近，许多动物储存食物，长出厚厚的皮毛，或冬眠以生存。

Hot and Cold: Temperate Zones The main feature of the climate in the temperate zones is dramatically different seasons. For example, Minneapolis, Minnesota, lies in the middle of a temperate zone. During summer, when the Northern Hemisphere is tilted toward the Sun, Minneapolis gets focused sunlight from a high angle in the sky. There are also more hours of daylight than darkness. This combination of focused sunlight and long days makes for hot summers. The record hottest day in Minneapolis is 42°C (108°F)! During winter, the Northern Hemisphere is tilted away from the Sun, and Minneapolis gets only low-angled sunlight spread over a larger area. It also experiences short days and long nights. Winters can be brutally cold, with a record low of -40°C (-40°F)! These dramatic seasonal swings do not happen near the poles or in the tropics.

热与冷:温带温带气候的主要特征是季节差异很大。 例如，明尼苏达州的明尼阿波利斯市位于温带的中部。 在夏季，当北半球向太阳倾斜时，明尼阿波利斯从天空的一个高角度获得聚焦的阳光。 白天的时间也比黑夜多。 这种集中的阳光和漫长的白昼相结合，造就了炎热的夏天。 明尼阿波利斯最热的一天是42°C(108°F)!在冬季，北半球远离太阳，明尼阿波利斯只有低角度的阳光照射在更大的区域。 它也经历了短白天和长黑夜。 冬天可能非常寒冷，创纪录的零下40°C(-40°F)!这种剧烈的季节性波动不会发生在两极附近或热带地区。