Cloud Seeding

Cloud Seeding

Vincent Schaefer an American chemist and meteorologist discovered the principle of cloud seeding in 1946.

It is a type of weather modification technique that improves the ability of clouds 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 newly formed snowflakes quickly grow and fall from the clouds back to the surface of the earth, increasing snowpack and streamflow.

In cloud seeding, the spreading of either dry ice or silver iodide aerosols by planes in the upper part of clouds stimulates the precipitation process and from rain. In this process, the aircraft sprays clouds with chemicals that condense smaller particles into large droplets of rain.
This process increases rainfall rates by around 10% to 30% per year.
Its effectiveness differs from different natures of projects, but long-term cloud seeding projects over the mountains of Nevada and other parts of the world have been shown to increase the overall snowpack in the targeted areas by 10 percent or more per year.

Methods of Cloud Seeding

Table of Contents

Methods of Cloud Seeding:

Hygroscopic Cloud Seeding
Static Cloud Seeding
Dynamic Cloud Seeding

Hygroscopic Cloud Seeding: In this method, the dispersion of salt is through the flares or explosives in the lower portion of the cloud. As a result, the salt increases its size as soon as the water joins with it.

By introducing Hygrogenic particles, it enhances the natural rain particles which begin a collision-coalescence process.
The hygroscopic material most commonly used is table salt. It is postulated that hygroscopic seeding causes the droplet size spectrum in clouds to become more maritime (bigger drops) and less continental, stimulating rainfall through coalescence.

Static Cloud Seeding: In this process, the spreading of chemicals such as silver iodide takes place into the clouds. The silver iodide turns crystals which moisture can condense. As moisture is already present in the clouds, silver iodide essentially makes rain clouds more effective at dispensing their water.

Dynamic Cloud seeding: This process is aimed at boosting the vertical air current, which encourages more water to pass through the clouds which results in more rain. As this process is based on a sequence of events working properly so this process is more complex than static cloud seeding.

Significances of Cloud Seeding in different areas:

The technique is used all over the world as a method for enhancing snowfall and increasing mountain snowpack, supplementing the natural water supply available to communities of the surrounding area.

It applies to various fields for various purposes like Agriculture, water pollution control, Air pollution control, power generation, fog dispersion, cyclone modification, hail suppression, etc. as Dry ice and silver iodide agents are effective in changing the physical chemistry of supercooled clouds.

Project Sky Water: In 1962, America’s project for weather modification through cloud seeding aimed at fog dispersal hail suppression, and cyclone modification.
Hygroscopic seeding for enhancement of rainfall in warm clouds is enjoying a revival, based on some positive indications from research in South Africa, Mexico, and elsewhere.
During the Popeye operation (march 1967-July 1972) of the US military, cloud-seeded silver iodide extended the monsoon season over North Vietnam, especially the Ho Chi Minh Trail, and it resulted in the targeted areas seeing an extension of the Monsoon period an average of 30 to 45 days.

Challenges in Cloud Seeding

Scientists are still studying the impacts of cloud seeding, So its overall environmental impact is difficult to measure due to the inability to perform controlled experiments along with the difficulty in direct tracing.

The cloud seeding technique uses various salts, and silver iodine crystals in the atmosphere, and the increased concentration of particulate matter or micropollutants increases the risk of respiratory illness.
It may cause flood in any particular area, for example, “Sharjah” city of UAE has experienced significant flooding.
These chemicals are potentially harmful to plants, and animals, and it impacts the environment.
It might change the climatic patterns by changing the real pattern of weather with the effect of the chemical used in this method.
The process can be a precursor of climatic changes and the greenhouse effect, which results in global warming. Even it is still an area of study.
To use the technique is also expansive for countries where rain is commonly not found in adequate amounts.

Cloud seeding in India:

Cloud seeding operations were conducted in India during the years 1983, 1984-1987, and 1993-94 by Tamil Nadu Govt due to severe drought.
Karnataka govt also used this technique in the years 2003 and 2004.
These operations were initiated in the same year through US-based Wheater modification year 2003-04.
Project Varshadhari in Karnataka in 2017 to provide relief in drought-affected areas.

Cloud Seeding in UAE (United Arab Emirates):

In recent times, UAE has used a new technique, combining shooting water-attracting salt flares with releasing salt nanoparticles, into the clouds to stimulate and accelerate the condensation process and hopefully produce droplets big enough to fall as rain.

The UAE govt. has developed a research program named UAE Research Program for Rain Enhancement Science in 2015 for research to improve cloud seeding technology.
It is used as a strategy by the UAE govt to address water challenges in the country.
The UAE is one of the first countries in the Persian Gulf region to use this technology.
UAE scientists use cloud seeding to supplement the water insecurity of the country, which stems from the extremely hot climate.
Scientists use weather radar to continuously monitor the atmosphere of the country.
They have estimated that cloud seeding operations can enhance rainfall by as much as 30%-35% in a clear atmosphere and up to 10-15 % in a more humid atmosphere.
This practice has caused concerns regarding the impact on the environment because it is difficult to predict the long-term global implications.
Flood is also common in this situation which affects the people of a certain area. In UAE many particular areas/cities got flooded after the use of this technique and it was a very difficult situation for the citizens living in those areas.

Reference: https://en.wikipedia.org/wiki/Cloud_seeding#Methodologies

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