图片来源：中国日报网
While small Cumulus do not rain, if you notice Cumulus getting larger and extending higher into the atmosphere, it's a sign that intense rain is on the way. This is common in the summer, with morning Cumulus developing into deep Cumulonimbus(thunderstorm) clouds in the afternoon.
虽然小的积云不下雨，但如果你注意到积云变大并向大气高处延伸，这预示着强降雨即将到来。这在夏季很常见，早晨的积云到了下午可能就变成了厚厚的积雨云（雷雨）。
Near the ground, Cumulonimbusare well defined, but higher up they start to look wispy at the edges. This transition indicates that the cloud is no longer made of water droplets, but ice crystals. When gusts of wind blow water droplets outside the cloud, they rapidly evaporate in the drier environment, giving water clouds a very sharp edge.
靠近地表时，积雨云的边界都比较分明，但到了大气高处，它们的边缘开始出现条缕状。这种转变预示着云朵不再由水滴组成，而是由冰晶构成。当一阵阵的风吹动云朵外层的水滴，水滴在干旱环境下就会迅速蒸发，让云朵边缘看上去很尖锐。
On the other hand, ice crystals carried outside the cloud do not quickly evaporate, giving a wispy appearance.
与此同时，云朵外层的冰晶却没有蒸发得那么快，于是就出现了条缕状的云朵外观。
Cumulonimbusare often flat-topped. Within the Cumulonimbus, warm air rises by convection. In doing so, it gradually cools until it is the same temperature as the surrounding atmosphere.
积雨云通常在顶部是平的。在积雨云内部，暖空气通过对流上升，在上升过程中逐渐冷却，直到和周围大气温度一致。
At this level, the air is no longer buoyant so cannot rise further. Instead it spreads out, forming a characteristic anvil shape.
上升到这个高度后，空气不再活跃，也不再上升，而是扩散开来，形成特有的砧形。
03
Cirrus 卷云
图片来源：中国天气网
Cirrusform very high in the atmosphere. They are wispy, being composed entirely of ice crystals falling through the atmosphere. IfCirrusare carried horizontally by winds moving at different speeds, they take a characteristic hooked shape.
卷云在大气高处形成。它们呈条缕状，完全由大气中落下的冰晶组成。如果卷云被运动速度不同的风水平吹动，它们会呈现特有的钩形。
Only at very high altitudes or latitudes do Cirrusproduce rain at ground level.
只有在非常高的高度或纬度，卷云才会化成雨降到地面。
But if you notice that Cirrusbegins to cover more of the sky, and gets lower and thicker, this is a good indication that a warm front is approaching. In a warm front, a warm and a cold air mass meet. The lighter warm air is forced to rise over the cold air mass, leading to cloud formation.
但如果你注意到卷云开始覆盖天空的大部分，位置变低，云块变厚，这预示着暖锋正在靠近。暖锋就是暖空气团和冷空气团相遇。重量更轻的暖空气团被迫升到冷空气团上方，导致卷云的形成。
The lowering clouds indicate that the front is drawing near, giving a period of rain in the next 12 hours.
云层变低预示着暖锋临近，在未来12个小时将会下雨。
04
Stratus 层云
图片来源：百度百科
Stratusis a low continuous cloud sheet covering the sky. Stratus forms by gently rising air, or by a mild wind bringing moist air over a cold land or sea surface.Stratus cloudis thin, so while conditions may feel gloomy, rain is unlikely, and at most will be a light drizzle.
层云是低低地覆盖天空的连续云层。层云由缓慢上升的空气形成，或是轻风将湿润空气吹过冰冷的地面或海平面形成。层云比较薄，所以尽管天气阴阴的，但却不太可能下雨，最多是毛毛雨。
Stratusis identical to fog, so if you've ever been walking in the mountains on a foggy day, you've been walking in the clouds.
层云和雾差不多，所以如果你曾在雾天上山，那就是云中漫步。
05
Lenticular 荚状云
