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Cloud seeding: All you need to know

Enhancing rainfall through weather modification technology.

cloud seeding - UAE

Cloud seeding has become a very popular tool now and you might be interested to know more about this sci-fi technique.

While humans cannot control weather, they can certainly modify it. Cloud seeding is one such type of weather modification, invented in the 1940s by General Electric (GE) scientists Vincent Schaefer and Irving Langmuir.

According to the reports released by the UN, about 14 per cent of the world population may face water scarcity by 2025. The World Meteorological Organisation reported that 56 countries employ cloud seeding technology to battle droughts and weather extremities. Let’s look more into this weather modification technology called cloud seeding.

What is a Cloud?

Clouds are made up of tiny water droplets or ice crystals that form when water vapor in the atmosphere cools and condenses around a tiny particle of dust or salt floating in the atmosphere. These tiny particles are known as condensation or ice nuclei, without which raindrops cannot form and precipitation will not form. It takes billions of these condensed water droplets to form a visible cloud. 

What is Cloud seeding?

Cloud seeding is a weather modification technique to enhance the clouds with condensation nuclei, which alter the microphysical processes within the cloud.

The technique improves cloud’s ability to produce rain by introducing these tiny particles, known as condensation nuclei into certain types of subfreezing clouds. Unattached supercooled water vapour molecules in the clouds condense around these particles. Then, the condensed water vapour droplets group together. This process continues until the droplets are large enough to fall as rain.

Cloud seeding
The global success rate of cloud seeding lies between 15 to 30 per cent.

Not all types of clouds are suitable for seeding. Clouds must be deep enough and of a suitable temperature (between -10 and -12 degrees Celsius) to be seeded effectively. 

The most common chemicals used for cloud seeding include silver iodide (AgI), potassium iodide and dry ice (solid CO2). The use of hygroscopic materials, such as table salt (NaCl) is more popular.

Scientists have found two main ways to conduct cloud seeding:

1. Drop particles from above the cloud

Cloud seeding chemicals may be dispersed by aircraft. For release by aircraft, payloads of chemicals like silver iodide flares are ignited and dispersed as an aircraft flies above the cloud. These flares, when released into the cumulus cloud formations accelerate condensation, forming water droplets weighing enough to create rainfall. 

Cloud seeding - two methods
Two methods of cloud seeding: 1. Release particles from the ground (below the clouds); 2. Drop particles from above the cloud

2. Release particles from below the cloud base

This method uses dispersion devices located on the ground (generators or canisters fired from anti-aircraft guns or rockets). When released by devices on the ground, the fine particles are carried downwind and upward by air currents after release.

Targeting warm cloud types, hygroscopic cloud seeding disperses salts through flares or explosives in the lower portions of clouds. 

Cloud seeding in the UAE

The UAE is one of the first countries in the Arab Gulf region to use cloud seeding technology, launching a cloud seeding program in 2002. Every rainfall in the UAE leads to a discussion on cloud seeding. The UAE scientists uses sophisticated weather surveillance radar (WSR) to continuously monitor the country’s atmosphere around the clock. 

Over the past two decades, the UAE has implemented an operational aircraft-based hygroscopic seeding program to compensate for its mean annual rainfall of less than 120 mm and to keep up with the increased demand for freshwater. 

Ground based-seeding generators in the UAE

Aside from the usage of a aircraft, the NCM has been using ground-based seeding generators in its rain enhancement operations in the UAE since March 2019. The ground generators are placed in the mountainous areas of the Hafeet and Fujairah areas, which are fitted with 48 special salt flares and fired into convective or warm clouds, accompanied by updraft or rising current of air. 

Cloud seeding in the UAE - ground based
The NCM launches aircrafts carrying salt crystals mixed with magnesium, sodium chloride and potassium chloride – that are shot into the clouds, once conducive clouds are identified.

The National Center of Meteorology (NCM) analyses cloud formations and weather data to find conducive clouds for cloud seeding. Once conducive clouds are found, NCM launches aircrafts carrying salt crystals – mixed with magnesium, sodium chloride and potassium chloride which are ‘seeded’ into clouds. The salt crystal flares then encourage the formation and release of cloud moisture, which then turns into precipitation.

Omar Al Yazeed, Director of Research at Training at the NCM, earlier explained that for a successful seeding, an aircraft is sent to the cumulus clouds in the early stages of development after experts forecast that they have the potential for rain. Once the data is collected, they conduct the seeding.

Drones to create artificial rain in the UAE

Traditionally in the UAE, cloud seeding uses natural salts hydroscopic agents that are shot into clouds to enhance rainfall. In 2021, the UAE has been using a new method of cloud seeding by using drones, which zap clouds with electricity.

These drones, equipped with a payload of electric-charge emission instruments and customized sensors, fly into clouds to give them an electric shock to trigger rain production. Jolting droplets in the clouds can cause them to clump together and fall as rain when they are big enough. As it eliminates the need for chemicals like silver iodide (which can be toxic to aquatic life), it serves a more eco-friendly seeding option.

This drone cloud seeding method produced a significant rainstorm in July 2021 in the UAE which was shared by NCM on Instagram.

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The UAE is aiming to become the global hub for rain enhancement that will improve water security in arid and semi-arid areas around the world. The cloud seeding projects, managed by the UAE Research Programme for Rain Enhancement Science (UAEREP) by the National Centre of Meteorology (NCM), continue to contribute to enhancing new knowledge of cloud seeding through dynamic scientific and technological innovations.