Few nations have embraced cloud-seeding as fervently as the UAE, which receives less than 100 millimetres of annual rainfall. But how does it work?
Here's everything you need to know about cloud-seeding in the Emirates:
What is cloud-seeding?
Cloud-seeding is simply a method of artificially encouraging a cloud to produce rain.
How does cloud-seeding work?
Planes are fitted with special flares that are loaded with salt crystals and fired into convective, or warm, clouds that have an updraft — or rising current of air.
The updraft then sucks up the salt crystals into the cloud, and they attract tiny particles of water that collide, becoming heavier and then falling as rain.
When was cloud-seeding first discovered?
In 1946, when a chemist with General Electric caused snow to fall after dropping dry ice into a cloud. Silver iodide, an alternative, is now commonly used in colder conditions, while in warmer temperatures, salt, or sodium chloride particles are preferred.
How much water can a cloud hold?
They may look light and fluffy, but clouds are actually incredibly heavy. The average rain cloud weighs as much as 100 elephants due to the weight of the water in them.
But because the droplets are tiny, and lighter than the air around them, the water often remains trapped inside. If they are high in the sky and the air is dry, they are unlikely to result in much rain.
The idea behind cloud-seeding is to encourage more rain to fall from the cloud by clumping the water droplets together, which makes them heavier and more likely to fall.
How often is cloud-seeding used in the UAE?
In short: a lot. According to the National Centre for Meteorology, cloud-seeding in the UAE started in the 1990s and has since placed an increasing focus on missions. Last year, the UAE conducted 242 missions, which was up from 177 in 2016.
Some would say the country has no choice — it receives less than 100 millimetres of annual rainfall. And it obtains practically all its drinking water from desalination, which is expensive.
Cloud-seeding is much cheaper by comparison, costing around 1 cent per cubic metre of water produced versus the 60 cents the UAE pays to desalinate the equivalent amount of water.
How effective is cloud-seeding?
According to the NCM, previous seeding operations have led to a 30 to 35 per cent increase in rainfall in ‘clean’ skies, and up to 15 per cent in a dusty atmosphere.
Because the UAE is so sandy, the latter outcome is more common.
In April 2013, intensive cloud-seeding operations in the Al Quaa region of Abu Dhabi coincided with a monthly rainfall of 136mm — which is significant given that the average April rainfall level for the area between 2003 and 2014 was just 29.9mm.
How has cloud-seeding changed over the years?
Scientists still use many of the same ingredients to precipitate rain, but they are searching for alternatives and techniques to improve the process.
The UAE Research Programme for Rain Enhancement Science was set up to do exactly that. It awards innovative projects and has received 365 proposals over three years.
The winners from the first $5m prize, handed out in 2016, will complete their projects in 2019. That research, which was presented at Abu Dhabi Sustainability Week, will soon be put into practice.
This article was first published on January 11, 2019.