understanding rain

Rain is a form of liquid precipitation, as opposed to non-liquid precipitation such as snow, ice and rock slit. Rain requires the presence of a thick layer of the atmosphere in order to meet a temperature above the melting point of ice near and above the Earth's surface. On Earth, the rain is the condensation of water vapor in the atmosphere of a grain of water heavy enough to fall and usually arrive on the mainland. The two processes may occur simultaneously to push the air gets saturated before the rain, which is cooling the air or adding water vapor to the air. Virga is precipitation that falls to the earth but evaporates before reaching the mainland; here's one way air saturation. Precipitation formed through collisions between grains of water or ice crystals with clouds. Rains pick grain sizes ranging from pepat, like pancakes (large grain), up to a small ball (small grains).
Moisture moving along zones of temperature and moisture differences in the so-called three-dimensional weather fronts is the major method of rain-making. If at that time there was moisture and upward motion is sufficient, the rain will fall from convective clouds (clouds with strong upward movement) as kumulonimbus (thunderstorms) which can be collected into a narrow rain bond. In mountainous areas, heavy rainfall could occur if the upstream side of the valley increased surface winds at a height which forces moist air to condense and fall as rain along the side of the mountain. On the leeward side of mountains, desert climates can occur due to the dry air caused by the flow down the valley resulting in the heating and drying of the air mass. The movement of the monsoon trump, or intertropis convergence zone, brings rainy seasons to savannah climate. Rain is the main source of fresh water in most parts of the world, providing suitable conditions for diverse ecosystems, as well as water for hydroelectric power generation and irrigation fields. Rainfall is calculated using rain gauges. The number of active rainfall calculated by weather radar and passively by weather satellites.
The impact of the urban heat island boost rainfall in the number and intensity under an urban wind. Global warming also resulted in changes in rainfall patterns around the world, including the atmosphere of rain in eastern North America and the dry atmosphere in the tropics. Rain is a major component of the water cycle and the main provider of fresh water on the planet. Rainfall global annual average is 990 millimetre (39 in). Climate grouping system such as system grouping Köppen climate using average rainfall yearly to help distinguish climatic zones. Antarctica is the driest continent on Earth. In other areas, the rain also fell with the content of methane, iron, neon, and sulfuric acid.