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Water-Rain
The mechanism by which clouds evolve and the
rainfall have been mentioned in many verses
of the holy quran.In each of these verses
some scientific points concerning these
natural phenomenon have been dealth with in
extreme beauty and delicacy.
The Formation of Rainfall :
Besides moderating the temperature,winds also
displace the humidity resulted from the seas
and damp areas.In order for these particles
of steam to return to the Earth,they should
turn into liquid and in the form of heavy
drops,so that they can get out of the clouds
and then fall to the ground.This requires
a drop in the temperature and also
hypersaturation of dampness in the air.The
drop in the temperature is usually brought
about as a result of the climb of the
currents of air,or because of the
neighbouring and mixing with cold currents
of air.The accumulation and piling up of
damp currents also cause the state of
hypersaturation of dampness in a region.
Of course,althogh the drop in temperature and
high humidity are essential for the rainfall
to happen they are not enough because in such
a case no clouds could ever evolve since
liquid drops would immediately separate from
the air and fall to the ground,and being
light enough,the fine drops would also remain
suspended in the air may be for days and
vaporize after being heated again.Another
important factor is the existence of nuclei
of distilation.Wind and waves cause the sea
water to spray into the air in fine droplets.
After the evaporation of these droplets fine
particles of salt remain suspended in the
air.These salt particles can absorb humidity,
and are infact centers for the accumulation
of humidity and the formation of rain drops.
To some extent dust and soot particles also
play the same role.The contact and the mixing
of these particles also accelerate the
process of the development of raindrops.
Bergeron the transfer of water vapor to
the solid surface of ice particles is
also another factor which causes the
formation and the acceleration in the
development of raindrops.
Rains are classified on the basis of such
criteria as the type of cloud they originate
from the kind of effective winds and the
diameter of drops.
For example,on the basis of the winds
affecting the rainfall,three types of
rain are recognized,
1- when the climb
of the wind is resulted from it contact
with ground ridges,that is highmountains,
the rain evolved is called mountainous
rain,which may be of two kinds: simple
or beach mountainous.
2- whenthe rain
forms following the contact between the
two cold and warm fronts of wind , the
possible rainfall is called frontal rain.
3- when the warm area and the humid warm air
cause a disturbance leading to rainstorms,
the rain is called storm rain.
There has also been a classification made on
the basis of the type of cloud originating
rain and the diameter of raindrops.For
example,drizzle evolves from nimbus clouds
which are near the ground and in a quiet
sky.Rainstorm is produced from cumulonimbus
clouds which are in high altitudes in this
kind of rain the diameter of the drops gets
bigger in the course of rainfall.Very heavy
rains known as showers fall briefly and
intermitenty,but an abundant amount of water
gets to the ground.
Other forms of precipitation such as snow and
hail might evolve depending on the condition
under which the rain falls.If the temperature
of the land on which,it rains drops a certian
amount because of a current of cold air or
elevation ,on their way the rain drops freeze
and turn into small solid crystalized
particles which one generally hexagonal and
are know as snow.Hail forms when falling
raindrops pass through a very cold air
stratum and hence freeze.
