Rain is liquid water in the form of droplets that have condensed fromatmospheric water vapor and then precipitated—that is, become heavy enough to fall under gravity. Rain is a major component of thewater cycle and is responsible for depositing most of the fresh wateron the Earth. It provides suitable conditions for many types ofecosystem, as well as water for hydroelectric power plants and cropirrigation.
The major cause of rain production is moisture moving along three-dimensional zones of temperature and moisture contrasts known asweather fronts. If enough moisture and upward motion is present, precipitation falls from convective clouds (those with strong upward vertical motion) such as cumulonimbus (thunder clouds) which can organize into narrow rainbands. In mountainous areas, heavy precipitation is possible where upslope flow is maximized withinwindward sides of the terrain at elevation which forces moist air to condense and fall out as rainfall along the sides of mountains. On the leeward side of mountains, desert climates can exist due to the dry air caused by downslope flow which causes heating and drying of the air mass. The movement of the monsoon trough, or intertropical convergence zone, brings rainy seasons to savannah climes.
The urban heat island effect leads to increased rainfall, both in amounts and intensity, downwind of cities. Global warming is also causing changes in the precipitation pattern globally, including wetter conditions across eastern North America and drier conditions in the tropics. Antarctica is the driest continent. The globally averaged annual precipitation over land is 715 mm (28.1 in), but over the whole Earth it is much higher at 990 mm (39 in). Climate classification systems such as the Köppen climate classification system use average annual rainfall to help differentiate between differing climate regimes. Rainfall is measured using rain gauges. Rainfall amounts can be estimated by weather radar.
Rain is also known or suspected on other planets, where it may be composed of methane, neon, sulfuric acid or even iron rather than water.
How does Rain Happen?
Rain is the primary source of fresh water for most areas of the world, providing suitable conditions for diverse ecosystems, as well as water for hydroelectric power plants and crop irrigation.
The phenomenon of rain is actually a water circle. The concept of the water cycle involves the sun heating the Earth's surface water and causing the surface 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 dry air. This is called virga, a phenomenon which is often seen in hot, dry desert regions.
Rain Advantage:
- Rain can make the plant growing faster
- Rain can make the supply of farmer's increase
- Rain can provides drinking water
- Rain will washes the dust on the ground and dirt
- Rain will clean the air
Rain Disadvantage:
- Rain will causes flood
- Rain probably will make people unemployed in a certain times
- Rain can cause erosion
- Rain can breeds mosquitos nests
