cloud seeding

IITM Pune demonstrates cloud seeding can produce rainfall

The approximate cost of producing water through cloud seeding was 18 paisa per litre; the cost will drop by more than 50% if we use indigenous seeding aircraft 

A cloud seeding experiment carried out in Solapur city

Cloud seeding

is a weather modification technique that aims to change the amount or type of precipitation that falls from clouds. It involves: 

• Spreading dry ice or silver iodide aerosols into the upper part of clouds
• Introducing tiny ice nuclei into certain types of subfreezing clouds
• Condensing smaller particles into larger rain droplets

Cloud seeding can help in areas that don't have a big enough supply of natural water. It can also control other weather events. 

expirement 

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,

 this was able to achieve 18% relative enhancement in rainfall, which is approximately 8.67mm more rainfall.

 The relative enhancement of accumulated rainfall was seen over two hours after seeding the clouds. 

 total enhancement of water availability through cloud seeding experiments was 867 million litres. 

name of The experiment and details

1 — Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX phase-4) —

 2 was a scientific investigation conducted in Solapur city during the summer monsoon period of 2018 and 2019. 

3 The primary objective was to investigate the efficacy of hygroscopic seeding in deep convective clouds and to develop a cloud seeding protocol.

Convective clouds

are clouds that form when warm, humid air rises through cooler air in the atmosphere. The warm air is less dense than the surrounding air, so it rises. This process is called convection.

4 The experiment used two aircraft for studying various cloud parameters and for seeding the clouds. 

The study found that 

 cloud seeding is an effective strategy for enhancing rainfall in a region under suitable conditions. 

what we used 

1 Convective clouds with a depth of over one kilometre and likely to evolve into deep cumulus clouds were targeted.

2 “We must indicate that the availability of a large number of samples (150/122 seed/no-seed) is a testimony / साक्ष्‍य to the rainfall enhancement through hygroscopic seeding with the physical conditions set in CAIPEEX,” the authors write.

3 Calcium chloride flare was used for seeding the clouds

 A cloud seeding flare releases these particles when triggered.

4 The seeding was done at the base of the warm convective clouds and at a time when the clouds were in their growing stage so that the seed particles could enter the clouds with minimum dispersion.

“The convective cloud bases

are found at 500-1,500 metres altitude during the summer monsoon period and around 2,000 metres or more altitude during the monsoon break periods, which depends on the moisture content in the lower atmosphere,”

 “Since the clouds are found at lower heights, the base of the convective clouds is warm, around 15 degrees C.”

“But cloud seeding alone cannot mitigate droughts but can help produce 18% more rainfall and partially address water requirements,” 

One of the most important findings of the study was 

that not all cumulus clouds produce rainfall when cloud seeding is done. 

“We found20-25% of cumulus clouds produce rainfall if cloud seeding is done correctly. 

The microphysics of clouds vary widely and so not all clouds produce rainfall through cloud seeding,” 

“Though the relative enhancement of rainfall was 46% as measured by automatic rain gauges,the actual increase in rainfall over a 100 sq.km area was only 18%,” says Dr. Prabhakaran.

cost 

cost-benefit ratio and foundthe approximate cost of producing water through cloud seeding was 18 paisa per litre. It was a research experiment and so we hired two aircraft from outside India for seeding the clouds.

 source the hindu