Rain - quite ordinary and all well familiar atmospheric phenomenon. It is an integral part of the global process known as water cycle in the nature. This process provides the invariance of volume of water resources of the planet. Circulation is possible only thanks to surprising properties of the water - at Earth it is present at all three aggregate states at the same time. However, everything told does not belittle importance at all, and even need of a rain for all live on the planet.
Formation of a cumulonimbus cloud
Formation of a cloud begins with steam formation process which in the nature happens constantly. The sun heats the earth and reservoirs and by that accelerates evaporation. The droplets which came off the water surface are so small that are kept above the ground by warm air flows. Light transparent steam mixes up with air masses and together with them directs up.
Meanwhile evaporation of water from the surface of the soil and reservoirs continues. Wind forces down together small flocks of fog. The cloudlet is formed. Tiny droplets of water vapor chaotically move, sometimes they merge and integrated at collisions. However it is not enough that the rain began.
That it occurred, drops have to become large and heavy so that the ascending air flows will not be able to hold them. One rain drop turns out at merge to one million other cloudy droplets. It is very long process. Cumulonimbus clouds are formed in the troposphere - most we string an atmosphere layer. The troposphere heats up from the earth therefore air temperature at the surface of the planet strongly differs from temperature in several kilometers over it – it falls on average on 6 °C on each kilometer of rise. Even during a summer heat at the height of 8-9 km over the Earth's surface really Arctic cold, and temperature of -30 °C here at all not a rarity reigns.
The processes happening in a cloud
The water vapor rising up together with air flows gradually cools down, and then and freezes, turning into the smallest kristallik of ice. Thus, in the top part of a cumulonimbus cloud there are ice crystals, and in lower - water droplets. In a cloud there is a condensation of water vapor. It is known that this process is possible only in the presence of any surface. Water vapor accumulates on the water droplets, various motes and motes lifted up by the ascending air flows and also on ice kristallika. The size and weight of kristallik quickly increases. They cannot keep in air any more and break down. When passing through thickness of a cloud the ice kristallik become even more and more significantly as condensation continues. If on the lower bound of a cloud above-zero temperature, small pieces of ice thaw and drop out on the earth in the form of a rain if minus – goes a hail. And further it is made a fresh start. Numerous rain streams form streams which fill up terrestrial reservoirs. Some part of the dropped-out moisture filters through the soil and gets to underground reservoirs. And a part of water evaporates, and the cloud is above the ground formed.