请问,用英语解释云的形成,

请问,用英语解释云的形成,

s are formed when air containing water vapor is cooled below a critical temperature called the dew point and the
resulting moisture condenses into droplets on microscopic
dust particles (condensation nuclei) in the atmosphere.
The air is normally cooled by expansion during its upward
movement. Upward flow of air in the atmosphere may be
caused by convection resulting from intense solar heating
of the ground; by a cold wedge of air (cold front) near the ground causing a mass of warm air to be forced aloft; or by a mountain range at an angle to the wind. Clouds are
occasionally produced by a reduction of pressure aloft or
by the mixing of warmer and cooler air currents.
海洋、湖面、植物表面、土壤里的水分，每时每刻都在蒸发，变成水汽，进入大气层。含有水汽的湿空气，由于某种原因向上升起。在上升过程中，由于周围空气越来越稀薄，气压越来越低，上升空气体积就要膨胀。膨胀的时候要耗去自身的热量，因此，上升空气的温度要降低。温度降低了，容纳水汽的本领越来越小，饱和水汽压减小，上升空气里的水汽很快达到饱和状态，温度再降低，多余的水汽就附在空气里悬浮的凝结核上，成为小水滴。如果温度低于冰点，多余的水汽就凝华成为冰晶或过冷却水滴。它们集中在一起，受上升气流的支托，飘浮在空中，成为我们能见到的云。