A Land of Contrasts
It's ironic that the wettest place in the world
manages to thirst for water each winter when no rain falls at all for
months at a time. The type of weather phenomenon that brings so much
rain to this part of the world is called the monsoons. Monsoons are
seasonal winds that blow from one direction for approximately six
months, bringing torrential rains, and then blow from the opposite
direction for the remaining six months, during which little rain falls.
During the wet season moist air is cooled as it blows over rising land,
letting abundant rain fall on the windward side of mountain ranges. But
because of widespread destruction of conifer forests that protected the
soil, the ground does not absorb the rain that falls so heavily during
the monsoon season. The city of Cherrapunji is 1290 meters above sea
level and much of the torrential rains run off the mountains into the
valley below. The irrigation system for the town of Cherrapunji is
insufficient to provide adequate amounts of clean, potable water from
below during the dry season. People who live there frequently have to
travel on foot for several kilometers to bathe and get drinking
What Causes so much Rainfall?
The oceans are the chief source of rain, but lakes
and rivers also contribute to it. The sun's heat evaporates the water.
It remains in the atmosphere as an invisible vapor until it condenses,
first into clouds and then into raindrops. Condensation happens when the
air is cooled. For raindrops to form there must be particulate matter in
the air, such as dust or salt, at temperatures above freezing. These
particles are called condensation nuclei.
When the nuclei are cooled to temperatures below the freezing point,
water condenses around them in layers. The particles become so heavy
they resist updrafts and fall through the clouds as rain.
In Cherrapunji it rains so much for two
Elevation: because of the
elevation of Cherrapunji, air that blows over the plains below is
cooled as it rises to the higher elevation. This cooling of the air
causes the moisture trapped in the air to condense, forming clouds,
which then release rain.
Monsoons: the prevailing winds in that part
of the world are very heavily laden with moisture. The constant supply
of moist air for six months straight results in almost continual
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