Lyla Lindsey
Australia has a very low annual average rainfall of 419 mm (16 in), with 80% of the land receiving less than 600 mm (24 in) of rainfall annually and 50% receiving less than 300 mm (12 in). The country has experienced frequent droughts, with the drought in Western Australia being the worst in 750 years. To combat water scarcity, Australians have turned to cloud seeding, a type of weather modification that aims to increase rainfall by dispersing substances like silver iodide, potassium iodide, and dry ice into the air to serve as cloud condensation or ice nuclei. While cloud seeding has been controversial due to its potential environmental impact and the difficulty in determining its effectiveness, it has been employed in various regions of Australia, including Tasmania, where it has achieved rainfall increases of up to 30%. Australian Rain Technologies (ART) is also developing ionization technology to enhance rainfall, with promising results.
| Characteristics | Values |
|---|---|
| Techniques | Cloud seeding, ionisation technology |
| Substances | Silver iodide, potassium iodide, dry ice, table salt |
| Methods | Static seeding, dynamic seeding, ionized aerosol introduction |
| Dispersion methods | Aircraft, ground-based generators, drones, infrared laser pulses |
| Trials | CSIRO trials (1947-early 1960s), Hydro Tasmania (1960s-present), Tasmanian experiments (Monash University), Chinese Olympics, University of Wollongong (Australia and Oman) |
| Regions with rainfall | Tasmania, Queensland, New South Wales, Western Australia, Kimberley |
| Climate | Tropical/subtropical, arid, semi-arid, temperate |
| Seasons | Wet and dry seasons in the tropical north, dry summers in the south, dry winters in the north |
| Rainfall | Annual average rainfall of 419 mm (16 in), 80% of land receives <600 mm, 50% of land receives <300 mm |
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What You'll Learn
Cloud seeding in Queensland and Tasmania
Queensland and Tasmania have both historically experienced water shortages and droughts, which have been exacerbated by reduced rainfall and increasing populations. As a result, both states have explored cloud seeding as a potential solution to enhance rainfall.
Queensland
The Queensland Cloud Seeding Research Program (QCSRP) was conducted in the southeast region of the state, near Brisbane, during the 2008/09 wet seasons. The program aimed to determine the characteristics of local cloud systems, document the properties of atmospheric aerosols, and assess the impact of cloud seeding on enhancing rainfall. The region has a diverse range of natural cloud systems, making it essential to understand this variability before drawing conclusions about the effectiveness of cloud seeding.
The QCSRP involved an exploratory randomized cloud seeding study, multiparameter radar measurements, and in-situ aircraft microphysical data collection. The program also assessed the impact of hygroscopic flare seeding on cloud-droplet growth, with results indicating that initial droplet spectra were altered by seeding, leading to larger drops.
Tasmania
Tasmania has a longer history of cloud seeding experiments, with the Commonwealth Scientific and Industrial Research Organisation (CSIRO) conducting trials in the state from 1947 to the early 1960s. Hydro Tasmania, the government-owned energy company, has also been involved in cloud seeding, particularly over lake catchments in central Tasmania.
In 2016, Hydro Tasmania confirmed it conducted a cloud seeding flight over the Derwent River catchment the day before flooding began in the area. This decision sparked controversy, with farmers and politicians asking the company to explain its actions, especially given the existence of flood warnings at the time. Hydro Tasmania described cloud seeding as a technique to increase precipitation by introducing particles into suitable clouds to encourage the formation and growth of ice crystals or raindrops.
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Cloud seeding: silver iodide and dry ice
Cloud seeding is a technique used to modify the weather by changing the amount or type of precipitation, mitigating hail, or dispersing fog. It involves dispersing substances into the air that serve as cloud condensation or ice nuclei. The usual objective is to increase rain or snow.
The most common chemicals used for cloud seeding include silver iodide, potassium iodide, and dry ice (solid carbon dioxide). Silver iodide is used because its crystalline structure is very similar to natural ice crystals. When silver iodide is put into the top part of a growing cloud, the crystal grows quickly once exposed to the cloud's moisture. The ice crystal then becomes a heavy, large raindrop, falls through the cloud, and reaches the ground. Dry ice is also effective in changing the physical chemistry of super-cooled clouds, making it useful in augmenting winter snowfall over mountains and, under certain conditions, in lightning and hail suppression.
In Australia, the Commonwealth Scientific and Industrial Research Organisation (CSIRO) conducted major cloud seeding trials between 1947 and the early 1960s. From 1947 to 1952, CSIRO scientists dropped dry ice into the tops of cumulus clouds, producing rain that would not have otherwise fallen. From 1953 to 1956, similar trials were carried out in South Australia, Queensland, and other states using both ground-based and airborne silver iodide generators. However, only the trial conducted in the Snowy Mountains produced statistically significant rainfall increases over the entire experiment.
Despite the potential benefits of cloud seeding, its effectiveness remains a subject of debate among scientists, with studies offering mixed results. While some projects have shown increased snowfall and rain in targeted areas, other studies suggest that cloud seeding has little to no impact on the amount of precipitation. Additionally, there are concerns about the environmental impact of cloud seeding, particularly on sensitive ecosystems and species like the pygmy possum in Australia.
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Rainfall enhancement through ionisation technology
Australia has a very low annual average rainfall of 419 mm (16 in). Its climate varies greatly, with four seasons across most of the country and a wet and dry season in the tropical north. The country has witnessed frequent droughts, with the one in Western Australia being the worst in 750 years.
To address water scarcity, Australia has been experimenting with cloud seeding since 1947. Cloud seeding is a technique to generate rain by dispersing substances like silver iodide, potassium iodide, and dry ice into the air, serving as cloud condensation or ice nuclei. While it has been successful in some regions, with rainfall increases of up to 30%, it is controversial due to environmental concerns and the difficulty in ascertaining its effectiveness.
As an alternative, Australian Rain Technologies (ART) has developed ATLANT™, a rainfall enhancement technology that uses ionization. This technology introduces ionized aerosols into clouds, accelerating the collision of cloud droplets and the formation of rainfall-sized droplets. It is harmless to humans and vegetation, and its sole impact on the atmosphere is to enhance rainfall.
The University of Wollongong has tested ART's ATLANT™ technology over ten years in Australia and Oman, identifying rainfall enhancement with high levels of statistical confidence. The technology is also cost-effective, requiring minimal power to operate, comparable to a television set.
With promising results, ART's ionization technology offers a potential solution to water shortages in Australia and worldwide.
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The impact of El Niño-Southern Oscillation
El Niño–Southern Oscillation (ENSO) is a global climate phenomenon that arises from variations in winds and sea surface temperatures over the tropical Pacific Ocean. These variations occur irregularly but do exhibit some cyclical patterns. ENSO affects the climate of the tropics and subtropics and has links to higher-latitude regions. The warming phase of the sea surface temperature is known as "El Niño", while the cooling phase is called "La Niña".
El Niño is associated with higher-than-normal air sea-level pressure over Indonesia, Australia, and the Indian Ocean extending to the Atlantic. It causes the Pacific jet stream to move southward and spread eastward, leading to warmer and drier conditions in the northern parts of North America and wetter conditions in the south. El Niño also impacts marine life by reducing or halting upwelling, which brings cold and nutrient-rich water to the surface. This reduction in upwelling affects the availability of phytoplankton, which has consequences for fish populations and, ultimately, everything that depends on them.
La Niña exhibits roughly the opposite pattern, with high pressure over the central and eastern Pacific and lower pressure in the tropics and subtropics. It causes the jet stream to move northward and weaken, leading to warmer and drier conditions in the southern United States and heavy rains and flooding in the Pacific Northwest and Canada. La Niña winters see warmer temperatures in the southern US and cooler temperatures in the northern regions. La Niña also results in colder waters off the Pacific coast, with higher nutrient content.
The occurrence of ENSO is unpredictable, and the phenomena typically last around a year each, with neutral periods in between. They occur every two to seven years, with El Niño events generally being more frequent than La Niña. The relative frequency of El Niño to La Niña events can influence global temperature trends over approximately ten-year periods. ENSO disrupts normal wind and rainfall patterns, leading to intense storms and droughts in different regions. The countries most affected by ENSO are developing nations bordering the Pacific Ocean, particularly those dependent on agriculture and fishing.
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Water-saving measures in Australia
Australia has been facing a severe water crisis, with some areas experiencing the worst drought in 750 years. The crisis has led to the implementation of various water-saving measures across the country.
One notable measure is the Murray-Darling Basin Balanced Water Fund, which aims to provide water security for farmers while protecting culturally significant wetlands and supporting threatened species or ecosystems. This initiative recognises the need to balance agriculture, finance, and the environment.
At the household level, Australians are encouraged to use water-efficient appliances and fixtures, such as washing machines, dishwashers, showers, taps, and toilets, which can help save money and keep water reserves sustainable. The Water Efficiency Labelling and Standards (WELS) scheme assists consumers in comparing the water efficiency of different products. For example, a 5-star showerhead that uses 6 litres per minute can save a significant amount of water and money on water bills annually.
Additionally, simple measures such as planting native gardens with low water requirements, training lawns to use less water, and covering outdoor pools or spas when not in use can also help conserve water.
While cloud seeding has been proposed as a potential solution to induce rainfall artificially, its effectiveness and environmental impact are controversial. Some studies indicate that it can increase rainfall, while others question its ability to alter rainfall patterns significantly.
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Frequently asked questions
Cloud seeding is a technique used to change the amount and type of precipitation, mitigate hail, or disperse fog. It involves dispersing substances like silver iodide, potassium iodide, and dry ice into the air to serve as cloud condensation or ice nuclei.
Australia has conducted major cloud seeding trials between 1947 and the early 1960s. Scientists dropped dry ice into cumulus clouds, producing rain. Cloud seeding experiments in Tasmania have been particularly successful, with rainfall increases of up to 30%.
While cloud seeding can increase the amount of ice in clouds, its effectiveness in altering rainfall patterns is controversial. Some studies suggest that it can enhance rainfall by up to 16.3%. However, it is challenging to determine if the rain is a direct result of cloud seeding.
Environmentalists worry about the impact of cloud seeding on sensitive ecosystems, such as the uptake of elemental silver affecting the pygmy possum and causing high-level algal blooms in pristine glacial lakes.
Australian Rain Technology (ART) has developed ATLANT™, a technology that introduces ionized aerosols into clouds, accelerating droplet collision and rainfall formation. This method is said to be harmless to humans and vegetation and has shown promising results in enhancing rainfall.
