Cloud Seeding: Can It Really Make It Rain And Help Clear Malaysia’s Haze?
Cloud seeding is not just about sprinkling salt or silver iodide in the sky, there are many more factors to consider to successfully make it rain.
- Cloud seeding encourages existing clouds to produce more rain by introducing particles that help water droplets grow and fall.
- While rainfall from cloud seeding can reduce haze, it does not extinguish fires, meaning smoke will continue if fires burn on.
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As Malaysia battles another bout of haze, you may have seen the term “cloud seeding” popping up in the news.
The idea sounds almost like something out of a sci-fi movie: send an aircraft into the sky, release some chemicals into the clouds, and hope rain comes pouring down.
But cloud seeding isn’t quite as simple as “spray stuff into the sky and make rain”.
With parts of Sarawak currently experiencing some of the country’s worst haze in years, authorities are preparing to use the technique in an effort to bring rainfall to affected areas.
So, how exactly does cloud seeding work? And can it actually help with the haze?
First, what is cloud seeding?
Cloud seeding is a form of weather modification designed to encourage existing clouds to produce more rain.
The important word here is existing.
Cloud seeding cannot create clouds out of thin air, nor can it magically produce rain from a completely clear blue sky.
Instead, it works by introducing tiny particles into suitable clouds to encourage water droplets to form, grow and eventually fall as precipitation.
According to the Malaysian Meteorological Department (MetMalaysia), substances such as sodium chloride, or ordinary salt, can act as cloud condensation nuclei — tiny particles around which water vapour can gather.
In other words, cloud seeding essentially gives the water vapour in a cloud something to “grab onto”.
So how does it actually make rain?
Think of a cloud as a giant collection of microscopic water droplets.
These droplets are incredibly tiny and don’t necessarily fall to the ground because they’re light enough to remain suspended in the air.
Cloud seeding introduces particles that encourage more water to condense around them.
As droplets collide and combine, they become larger and heavier.
Eventually, they become heavy enough to fall as rain.
MetMalaysia explains that cloud droplets can undergo repeated collision and coalescence, allowing them to grow until they eventually fall from the cloud as precipitation.
There is another method used in colder clouds, where substances such as silver iodide can encourage supercooled liquid water to freeze into ice particles. Those particles can then grow and eventually fall as precipitation.
So, despite the dramatic name, cloud seeding isn’t really creating rain.
It is more like giving a suitable cloud a helping hand to rain more efficiently.
How do they seed the clouds?
This is where aircraft come in.
Specially equipped aircraft can release the seeding material into or around suitable clouds.
The material used depends on the type of cloud and the weather conditions.
For Malaysia’s operations, hygroscopic materials such as salt are commonly associated with precipitation enhancement. MetMalaysia says sodium chloride can attract and retain water vapour, helping the formation and growth of cloud droplets.
So, how can cloud seeding help with the haze?
This is where things get interesting.
Rain can help wash airborne particles out of the atmosphere.
When sufficient rain falls, some of the smoke and particulate matter suspended in the air can be removed through a process known as wet deposition.
So, if cloud seeding successfully produces rainfall over a haze-affected area, it can potentially help improve air quality by bringing some of those particles down.
It can also help wet forests, peatlands and other areas affected by fires, potentially making firefighting efforts easier.
But there’s an important distinction: Cloud seeding does not put out the fires by itself.
If fires continue burning — particularly large forest and peat fires — smoke will continue being produced.
That means rainfall is only part of the solution.
When will Malaysia carry out the cloud seeding?
The government has announced that cloud-seeding operations will be carried out in stages from 3 to 5 September across 13 areas in Sarawak, Kedah and Perlis.
In Sarawak, the operation will cover areas including Batang Ai, Bakun, Murum, Bengoh, Gerugu, Assyakirin, Sika and Matang.
In Kedah, operations will target the Pedu, Muda, Ahning and Beris dams, while the Timah Tasoh Dam in Perlis will also be targeted.
The operations will involve the National Disaster Management Agency (NADMA), MetMalaysia and the Royal Malaysian Air Force.
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