點解會下雨(要英文)10點

Rain is a type of precipitation - a product of the condensation of atmospheric water vapor that is released on the Earth's surface.

It forms when separate drops of water fall to the Earth from clouds. Not all rain reaches the surface; some of it evaporates while falling through dry air. When none of it reaches the ground, it is called virga, a phenomenon often seen in hot, dry desert regions.

Rain plays a role in the hydrologic cycle in which moisture from the oceans evaporates, condenses into drops, precipitates (falls) from the sky, and eventually returns to the ocean via rivers and streams to repeat the cycle again. The water vapor from plant respiration also contributes to the moisture in the atmosphere.

A major scientific explanation of how rain forms and falls is called the Bergeron process. More recent research points to the influence of Cloud condensation nuclei released as the result of biological processe

1) Evaporation
On Sunny days, the sun heats up the sea water. The water changes from liquid to vapour. Warm air carries the vapour up to the sky. A convection current forms.
2) Condensation
The upper part of the sky is cooler. This condenses the water vapour to form small droplets of liquid water. Droplets of water join to form clouds.
3) Transportation
The clouds are carried to other places by the wind.
4) Raining
Small pieces of cloud scan join together. This makes the cloud heavy. The water droplets may fall to the ground as rain.

2008-05-17 13:04:25 補充：
In nature, water also undergoes similar changes. This forms the water cycle. In the cycle, water does not boil but evaporates when it absorbs heat energy from the sun.