A light aircraft takes off from an airfield in northern Dubai with dozens of canisters attached to its wings. It heads towards a cloud in the distance into which it disappears. Scientists in a control room on the ground monitor sophisticated radar and crunch data before directing the pilot to a spot inside the cloud where the canisters ignite to release salt nano-particles. Sometime later, and several miles away, it starts to rain.
This is the round-the-clock cloud seeding project being run by UAE’s National Center of Meteorology (NCM). The salt particles supercharge condensation inside the cloud and scientists are confident that this rain enhancement technique increases rainfall in certain clouds over the Emirates by anywhere up to 30 per cent.
Research done at NCM puts the UAE at the forefront of global rain enhancement science and the program is set to expand as earlier this month NCM procured more aircraft capable of carrying larger quantities of cloud seeding materials.
The turboprop planes are also equipped with sophisticated safety systems and represent ‘an important milestone in the NCM strategy to enhance its capabilities in the field of cloud seeding, expanding cloud seeding operations, and contributing to achieving water security for the UAE,’ according to a statement.
Cloud seeding creates artificial rain but only works in clouds of a specific type that have already formed. Once a suitable cloud has been identified, aircraft are scrambled to disperse water-attracting particles which stimulate and accelerate condensation and enhance rainfall.
While the practice was once seen as a novelty, it is becoming increasingly widespread, with nations such as the USA, Russia, China, India, Israel, South Africa and Australia using cloud seeding to stimulate both rain and snow.
Climate projections forecast that the UAE will become hotter and drier in the coming years, with annual average temperatures predicted to increase by between 1.5 and 2°C by 2040. Meanwhile the UAE’s total annual water demand is estimated to double by 2030, from 4.5 billion cubic meters (bcm) per year currently to between 9 and 10 bcm, placing immense pressure on the nation’s desalination infrastructure. When these factors are considered, it is easy to see why cloud seeding has become an important factor in future water provision strategy.
Khalifa University’s Dr Steve Griffiths is a strategic advisor to the UAE Research Program for Rain Enhancement Science. He admits that when he first began looking at the impact seeding programmes had he was sceptical.
‘But when you look at the data it is pretty conclusive that you can increase rainfall by anywhere between 5 – 30 per cent in clouds that are predisposed to have rain, which can equate to hundreds of millions of cubic metres of water,’ he tells The Ethicalist:. ‘When I started looking at the numbers, I realised that the impact can be meaningful. It’s not going to replace desalination and good agricultural practice and water management, but it is another arrow in the quiver. It makes sense.’
Cloud Seeding Strategy
The UAE cloud seeding program, implemented by NCM follows the conventional approach of igniting hygroscopic flares composed of natural salts (primarily potassium chloride) at the base of convective clouds near the updraft core.
Launched in 2002, the program targeted frequent summertime convection along the north-eastern Hajar mountains. The program infrastructure subsequently expanded over the years until radar was used extensively to identify suitable clouds year-round over the entire Emirates from 2010 onwards. The nation has so far invested $18 million (around Dh66million) in rain enhancement projects and now performs around 1,000 hours of cloud seeding each year.
Meteorologists conclude that the UAE’s cloud seeding programme has increased average annual rainfall by between 10 to 15 per cent.
While the process is viewed positively in the UAE with no evidence that it causes flooding or pollution, it has been controversial elsewhere as a form of weather modification where it has several applications, including being used to clear fog from airports, fight forest fires and even divert rainfall, as was the case in China during the 2008 Beijing Olympics.
There have been concerns that another method, which uses silver iodide to stimulate ice crystal formation, adds pollutants to water systems. Silver iodide is known to be toxic and in the US is regulated under the Clean Water Act as a hazardous substance.
Cloud seeding is not a new technology. The first experiments took place in the 1940s. It fell out of favour in the 1980s for being an ‘unacceptable ethical and environmental hazard,’ but has recently seen renewed interest.
There are still some doubts, however, and the science remains incomplete. In a recent article published in the Bulletin of the Atomic Scientists, Laura Kuhl, Assistant Professor of Public Policy and Urban Affairs and International Affairs, addressed concerns that the practice has effects for regions downwind of seeded weather systems.
She wrote: ‘While cloud seeding is often described as ‘creating’ rain, it can be more accurately described as moving rain from one location to another, and cloud seeding may simply redistribute risk. Cloud seeding condenses water that is already present in cloud formations. As such, some have argued that cloud seeding cannot impact hydrological cycles at a large scale.
‘But the American Meteorological Society acknowledges that while there is currently no evidence of downwind impacts, these cannot be ruled out, and that “activities conducted for the benefit of some may have an undesirable impact on others”.’
Indeed, even successful programs have limitations. While cloud seeding is considerably cheaper than desalination – converting saline water (generally sea water) into fresh water – the UAE (a high-level comparison estimates that a cubic metre of seeded water costs $0.01 as opposed to $0.31/m3 from desalination), it does not create water exactly where it is needed. And only a specific type of cloud is suitable.
As Dr Griffiths explains: ‘You have to be able to collect the water and use it. With desalination you can produce water and transport it to where you need it. Rain doesn’t always go where you want it to go so you can’t collect every drop. We have the design architecture so we can quickly identify a cloud amenable to hydroscopic seeding and we can get more rain and more area coverage, but you can’t push that cloud around. You can’t direct the rain in a specific area. However, as the science develops you start to see the potential of seeding making a meaningful contribution to rainfall.’
The game changer, it is believed, will be when scientists develop a reliable process to actually make clouds, which can then be seeded. This might sound like sci-fi, but it is already happening in part, with tests previously carried out in the UAE.
‘What you have to do is create a moist updraft that goes high enough for condensation to occur, which can produce a rain cloud and rain over your agricultural area or reservoir,’ explains Dr Griffiths. ‘We did a project where we placed what was basically an inverted airplane jet engine pointed at the sky and placed seeding material in it and tried to create a rain cloud. It is pushing the science. You still have to have precise atmospheric conditions, but it is in the realm of possibility and we are currently looking at that avenue, which is very exciting.’
In the meantime, NCM is developing new technology using drones and computer technology to make seeding more accurate, cost-effective and autonomous. It is hoped that in the future, low-maintenance, self-contained autonomous cloud seeding projects can be established in developing nations that do not have the funds or pilots for their own facilities.
These will use radar technology, satellite data and weather forecasting algorithms to detect suitable clouds and dispatch drones to identify, verify and seed them. Work is already taking place in sub-Saharan Africa to this effect.
And there may also be opportunities to use the science to help populations in areas prone to flooding, as evidence shows that adding particles to clouds can also create a reverse rainfall process.
‘When you start to get into cloud chemistry, physics, and dynamics there is an optimal particle size for seeding. If you have too much fine particulate matter in the air, it is hard to stimulate rain. It suppresses rainfall,’ explains Dr Griffiths. ‘You can take the science and impede or hinder rainfall. You can leverage the science for interventions that go in the other direction.’
A responsible approach is paramount as weather modification could have untold unforeseen repercussions on an already fragile climate, which is why the cloud seeding program in the UAE is strictly following the science. But as long as it is safe and effective, those small aircraft that disappear inside clouds at opportune moments throughout the year could help solve a looming problem for one of the driest regions on the planet.
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