Rain is
liquid water
in the form of droplets that have condensed
from atmospheric
water vapor
and then precipitated—that is, become heavy enough to fall under gravity.
Rain is a major component of the water cycle
and is responsible for depositing most of the fresh water
on the Earth. It provides suitable conditions for many types of ecosystem,
as well as water for hydroelectric power plants and crop irrigation.
The major cause of
rain production is moisture moving along three-dimensional zones of temperature
and moisture contrasts known as weather 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 within windward 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?
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 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
