CLOUD
SEEDING - GEOGRAPHY
News: IITM Pune demonstrates
cloud seeding can produce rainfall
What's
in the news?
● A
cloud seeding experiment carried out in Solapur city, which falls on the
leeward side of the Western Ghats and hence gets low rainfall — 384 mm and 422
mm of total rainfall during the period June to September 2018 and 2019,
respectively — was able to achieve 18% relative enhancement in rainfall, which
is approximately 8.67mm more rainfall.
Cloud
seeding:
● Cloud
seeding is a weather modification
technique that improves a cloud's ability to produce rain or snow by
introducing tiny ice nuclei into certain types of subfreezing clouds. These
nuclei provide a base for snowflakes to form.
● The
primary goal of it is to enhance precipitation in areas facing water shortages,
droughts, or where water resources are critical for agriculture, hydroelectric
power generation, or other purposes.
How
cloud seeding works?
● A
minute amount of silver iodide is sprayed across propane flame.
● Silver
iodide particles rise into clouds.
● Silver
iodide causes cloud moisture to freeze and create ice crystals.
● Ice
crystals grow big enough to fall as snow.
Chemicals
used:
● Silver
iodide
● Potassium
iodide
● Dry
ice (solid carbon dioxide)
Different
methods of cloud seeding:
1.
Hygroscopic Cloud Seeding:
● In
this, salts are dispersed through flares or explosives in the lower portions of
clouds.
● It
promotes the coalescence process
using hygroscopic salt nuclei to increase the precipitation efficiency of
clouds.
2.
Static Cloud Seeding:
● It
involves spreading a chemical like silver iodide crystals into clouds.
● The
crystal provides hygroscopic salt around which moisture can condense.
● The
moisture already present in the clouds essentially makes rain clouds more
effective at dispensing their water.
3.
Dynamic Cloud Seeding:
● It
boosts vertical air currents, which encourages more water to pass the clouds
which translates into more rain.
● It
is more complex than static cloud seeding because it depends on a sequence of
events working properly.
● It
uses 100 times more ice crystals than those used in the static method.
Issues
in Cloud Seeding:
● Some
chemicals are potentially harmful to the
natural environment and the plants which depend on the contaminated rain to
produce food.
● Very
expensive process.
● It
could have many dire consequences to the environment if not well regulated.
● Clouds
have to be present, not just any cloud but clouds capable of producing rain.
● The
atmospheric conditions must also suit the process as certain conditions could
lead to an unwarranted result like the rain falling in a different location or
not falling at all.