68 Thunderstorms-High

Thunderstorms FOCUS Question What causes thunderstorms?

雷暴焦点问题雷暴是由什么引起的?

A Dark and Stormy Night Zap! Lightning streaks across the sky. Boom! Thunder rattles the windows. A thunderstorm can be exciting, but it can also be dangerous. Heavy rain can cause floods. Lightning can strike houses, trees, and even people. Thunderstorms start out like any other rainstorm. The Sun warms up moist air near the ground. The warm air rises and sends water vapor toward the sky. High in the sky, the vapor cools and condenses into tiny water droplets to form a cloud. But unlike common rain clouds, thunderclouds grow tall and develop electrical charges. Here's how it works.

一个黑暗和暴风雨的夜晚!闪电划过天空。 繁荣!雷声震得窗户格格作响。 雷雨可能令人兴奋，但也可能很危险。 大雨会引起洪水。 闪电可以击中房屋、树木，甚至人。 雷暴开始时和其他暴雨一样。 太阳使地面附近的潮湿空气升温。 暖空气上升，把水蒸气送到天空。 在高空，蒸汽冷却并凝结成微小的水滴形成云。 但与常见的雨云不同的是，雷雨云会变高并产生电荷。 下面是它的工作原理。

A Charged-Up Cloud A thundercloud begins to form when warm, moist air rises into the sky. The rising air creates an updraft. Near the top of the cloud, the air is cold. This cold air is heavy, so it sinks through the cloud, creating a downdraft. Water droplets that have turned to ice also fall through the cloud. Meanwhile, more warm, moist air rises up. The cloud grows taller and becomes a thundercloud, or cumulonimbus cloud. As the updraft and downdraft move within the cloud, dust, water droplets, and ice bump into each other. These particles rub together and become electrically charged.

当温暖潮湿的空气升入天空时，雷雨云就开始形成。 上升的空气形成上升气流。 靠近云顶的地方，空气是冷的。 这种冷空气很重，所以它在云层中下沉，形成了下沉气流。 凝结成冰的水滴也会穿过云层落下。 与此同时，更多温暖潮湿的空气上升。 云越长越高，变成了雷雨云或积雨云。 当上升气流和下降气流在云内移动时，灰尘、水滴和冰就会相互碰撞。 这些粒子相互摩擦而带电。

It's Electrifying! Have you ever felt a shock after walking across a rug in your socks? That shock is a tiny zap of static electricity. Lightning is a much bigger zap. In a thundercloud, positive electrical charges build up near the top. Negative charges build up in the middle and near the bottom of the cloud. Just like in a magnet, positive and negative charges attract each other. Lightning happens when a group of negative charges jump toward the positive charges. Lightning can occur within a cloud, or it can move from one cloud to another cloud. It can also spark between a cloud and the ground.

这是惊人的!你曾经穿着袜子走在地毯上时感到震惊吗? 这种电击是一种微小的静电。 闪电的杀伤力要大得多。 在雷雨云中，正电荷在顶部附近聚集。 负电荷聚集在云的中间和底部附近。 就像磁铁一样，正电荷和负电荷相互吸引。 当一群负电荷跳向正电荷时，闪电就发生了。 闪电可以在云内发生，也可以从一片云移动到另一片云。 它也可以在云层和地面之间产生火花。

Bolt and Boom! Lightning is almost always followed by thunder. That loud clap happens because lightning releases a lot of energy. The air near the bolt becomes extremely hot, making it suddenly expand. As the air quickly cools, it contracts. This collapsing air makes a boom that we hear as thunder. Light travels much faster than sound. If lightning strikes nearby, you will hear a loud crack of thunder at the same moment you see the flash. If lightning strikes in the distance, you will see it right away, but the thunder will rumble a few seconds later. Math Moment Each second between seeing lightning and hearing thunder represents about 300 meters (984 ft.) between you and the bolt. How far away is the bolt if you count 5 seconds between the flash and the boom?

嘭!闪电之后几乎总是雷声。 这种响亮的拍击声的发生是因为闪电释放了大量的能量。 螺栓附近的空气变得非常热，使螺栓突然膨胀。 当空气迅速冷却时，它就会收缩。 空气的坍缩发出轰隆声，我们听到的就像打雷一样。 光比声音传播得快得多。 如果闪电击中附近，在你看到闪电的同时，你会听到一声巨响。 如果远处有闪电，你马上就能看到，但几秒钟后雷声就会隆隆作响。 看到闪电和听到雷声之间的每一秒代表你和闪电之间大约300米(984英尺)。 如果从闪电到爆炸间隔5秒，闪电有多远?

Types of Thunderstorms A towering thundercloud is also called a cell. Single cell thunderstorms create short bursts of rain with a lot of wind and some lightning. A storm with just one cell won't last long. When single cells join together, a multicell storm forms. Multicell thunderstorms can be very strong and last for a long time. As one cell begins to die down, another cell gains strength, dropping even more rain and producing more lightning. The strongest type of thunderstorm comes from a supercell. Supercells happen when the strong updraft twists inside the cell. Supercells are rare and can lead to tornadoes.

雷暴的类型高耸的雷云也被称为云胞。 单细胞雷暴产生短时间的降雨，伴随着大量的风和一些闪电。 只有一个细胞的风暴不会持续太久。 当单个细胞结合在一起时，就形成了多细胞风暴。 多细胞雷暴可以非常强烈，持续很长时间。 当一个细胞开始消亡时，另一个细胞开始增强，落下更多的雨水，产生更多的闪电。 最强类型的雷暴来自超级单体。 当强烈的上升气流在细胞内扭转时，超级细胞就产生了。 超级单体是罕见的，可以导致龙卷风。