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    Rain is the primary source of fresh water for most areas in the world. It provides suitbale conditions for diverse ecosystems as well as water for hydroelectric power plants and crop irrigation. The phenomenon of rain is actually a water cycle. The concept of water cycle involves the sun's heating on the earth's surface water, and it causes the water to evaporate. The water vapor rises into the earth's atmosphere. The water in the atmosphere cools and condenses into liquid droplets. The droplets grow until they are heavy and fall to the earth as precipitation which can be in the form of rain or snow. However, not all rain reaches the surface. Some evaporates while falling through the air. This is called virga, a phenomenon which is often seen in hot, dry desert regions.

source: freeenglishcourse.info

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