The answer to our regular droughts? Rainmaking?

[N.O.R.F]

Cloud seeding

 

Cloud seeding, a form of weather modification, is the attempt to change the amount or type of precipitation that falls from clouds, by dispersing substances into the air that serve as cloud condensation or ice nuclei. The usual intent is to increase precipitation, but hail suppression is also widely practiced. Silver iodide and dry ice are the most commonly used substances in cloud seeding.

 

How cloud seeding works

 

The most common chemicals used for cloud seeding include silver iodide and dry ice (frozen carbon dioxide). The expansion of liquid propane into a gas is being used on a smaller scale. The use of hygroscopic materials, such as salt, is increasing in popularity because of some promising research results.

 

Seeding of clouds requires that they contain supercooled liquid water--that is, liquid water colder than zero degrees Celsius. Introduction of a substance such as silver iodide, which has a crystalline structure similar to that of ice, will induce freezing (heterogeneous nucleation). Dry ice or propane expansion cools the air to such an extent that ice crystals can nucleate spontaneously from the vapor phase. Unlike seeding with silver iodide, this spontaneous nucleation does not require any existing droplets or particles because it produces extremely high vapor supersaturations near the seeding substance. However, the existing droplets are needed for the ice crystals to grow into large enough particles to precipitate out.

 

In mid-latitude clouds, the usual seeding strategy has been predicated upon the fact that the equilibrium vapor pressure is lower over water than over ice. When ice particles form in supercooled clouds, this fact allows the ice particles to grow at the expense of liquid droplets. If there is sufficient growth, the particles become heavy enough to fall as snow (or, if melting occurs, rain) from clouds that otherwise would produce no precipitation. This process is known as "static" seeding.

 

Seeding of warm-season or tropical cumuliform (convective) clouds seeks to exploit the latent heat released by freezing. This strategy of "dynamic" seeding assumes that the additional latent heat adds buoyancy, strengthens updrafts, ensures more low-level convergence, and ultimately causes rapid growth of properly selected clouds.

 

Cloud seeding chemicals may be dispersed by aircraft or by dispersion devices located on the ground (generators). For release by aircraft, silver iodide flares are ignited and dispersed as an aircraft flies through a cloud. When released by devices on the ground, the fine particles are downwind and upwards by air currents after release.

 

While cloud seeding has shown to be effective in altering cloud structure and size, and converting cloud water to ice particles, it is more controversial whether cloud seeding increases the amount of precipitation at the ground. Part of the problem is that it is difficult to discern how much precipitation would have occurred had the cloud not been "seeded". In other words, it is hard to discern additional precipitation from seeding from the natural precipitation variability, which is frequently much greater in magnitude. Nevertheless, there is more credible scientific evidence for the effectiveness of winter cloud seeding over mountains (to produce snow) than there is for seeding warm-season cumuliform (convective) clouds. This statement is supported by the professional societies Weather Modification Association, World Meteorological Organization, and American Meteorological Society (AMS). The AMS further states that there is statistical evidence for seasonal precipitation increases of about 10% with winter seeding [1].

 

The National Center for Atmospheric Research (NCAR), an institution in Boulder, Colorado, has made some statistical analysis of seeded and unseeded clouds in an attempt to understand the differences between them. They have conducted seeding research in several countries that include Mexico, South Africa, Thailand, Italy, and Argentina.

 

Cessna 210 with cloud seeding equipment

 

History

 

The first attempt at cloud seeding was in upstate New York in 1946. Vincent Schaefer, a General Electric chemist, caused snow to fall near Schenectady, NY after he dumped six pounds of dry ice into a cloud from a plane.[1] Noted atmospheric scientist Bernard Vonnegut (brother of novelist Kurt Vonnegut) is credited with discovering the potential of silver iodide for use in cloud seeding. This property is related to a good match in lattice constant between the two types of crystal (the crystallography of ice later played a role in Kurt Vonnegut's novel Cat's Cradle). Silver iodide is mostly used for winter snowfall augmentation over mountains and hail suppression. While not a new technique hygroscopic seeding for enhancement of rainfall in warm clouds is enjoying a revival, based on some positive indications from research in South Africa, Mexico, and elsewhere. The hygroscopic material most commonly used is salt. It is postulated that hygroscopic seeding causes the droplet size spectrum in clouds to become more maritime (bigger drops) and less continental, stimulating rainfall through coalescence.

 

From March 1967 until July 1972, the US military Operation Popeye cloud seeded silver iodide to extend the monsoon season over North Vietnam, specifically the Ho Chi Minh Trail. The operation resulted in the targeted areas seeing an extension of the monsoon period an average of 30 to 45 days.[2] The 54th Weather Reconnaissance Squadron carried out the operation to "make mud, not war." [3]

 

One private organization which offered, during the 1970s, to conduct weather modification (cloud seeding from the ground using silver iodide flares) was Irving P. Crick and Associates of Palm Springs, California. They were contracted by the Oklahoma State University in 1972 to conduct such a seeding project to increase warm cloud rainfall in the Lake Carl Blackwell watershed. That lake was, at that time (1972-73), the primary water supply for Stillwater, Oklahoma and was dangerously low. The project did not operate for a long enough time to show statistically any change from natural variations. However, at the same time, seeding operations have been ongoing in California since 1948.

 

An attempt by the United States military to modify hurricanes in the Atlantic basin using cloud seeding in the 1960s was called Project Stormfury. Only a few hurricanes were tested with cloud seeding because of the strict rules that were set by the scientists of the project. It was unclear whether the project was successful; hurricanes appeared to change in structure slightly, but only temporarily. The fear that cloud seeding could potentially change the course or power of hurricanes and negatively affect people in the storm's path stopped the project.

 

Two Federal agencies have supported various weather modification research projects, which began in the early 1960s: The United States Bureau of Reclamation (Reclamation; Department of the Interior) and the National Oceanic and Atmospheric Administration (NOAA; Department of Commerce). Reclamation sponsored several cloud seeding research projects under the umbrella of Project Skywater from 1964-1988, and NOAA conducted the Atmospheric Modification Program from 1979-1993. The sponsored projects were carried out in several states and two countries (Thailand and Morocco), studying both winter and summer cloud seeding. More recently, Reclamation sponsored a small cooperative research program with six Western states called the Weather Damage Modification Program [4], from 2002-2006.

 

Funding for research has declined in the last two decades. A 2003 study by the United States National Academy of Sciences urges a national research program to clear up remaining questions about weather modification's efficacy and practice.

 

In Australia, CSIRO conducted major trials between 1947 and the early 1960s:

 

1947 – 1952: CSIRO scientists dropped dry ice into the tops of cumulus clouds. The method worked reliably with clouds that were very cold, producing rain that would not have otherwise fallen.

1953 – 1956: CSIRO carried out similar trials South Australia, Queensland and other States. Experiments used both ground-based and airborne silver iodide generators.

Late 1950s and early 1960s: Cloud seeding in the Snowy Mountains, on the Cape York Peninsula in Queensland, in the New England district of New South Wales, and in the Warragamba catchment area west of Sydney.

Only the trial conducted in the Snowy Mountains produced statistically significant rainfall increases over the entire experiment.

 

 

[edit] Modern uses

The largest cloud seeding system in the world is that of the People's Republic of China, which believes that it increases the amount of rain over several increasingly arid regions, including its capital city, Beijing, by firing silver iodide rockets into the sky where rain is desired. There is even political strife caused by neighboring regions which accuse each other of "stealing rain" using cloud seeding[5]. About 24 countries currently practice weather modification operationally.

 

In the United States, cloud seeding is used to increase precipitation in areas experiencing drought, to reduce the size of hailstones that form in thunderstorms, and to reduce the amount of fog in and around airports. Cloud seeding is also occasionally used by major ski resorts to induce snowfall. Eleven western states and one Canadian province (Alberta) have ongoing weather modification operational programs [6]. In January 2006, an $8.8 million cloud seeding project began in Wyoming to examine the effects of cloud seeding on snowfall over Wyoming's Medicine Bow, Sierra Madre, and Wind River mountain ranges. [7]

 

A number of commercial companies, such as Aero Systems Incorporated [8], Atmospherics Incorporated [9], North American Weather Consultants [10], Weather Modification Incorporated [11], Weather Enhancement Technologies International [12] offer weather modification services centered on cloud seeding. The USAF proposed its use on the battlefield in 1996, although the U.S. signed an international treaty in 1978 banning the use of weather modification for hostile purposes.

 

In Australia, CSIRO’s activities in Tasmania in the 1960s were successful. Seeding over the Hydro-Electricity Commission catchment area on the Central Plateau achieved rainfall increases as high as 30% in autumn. The Tasmanian experiments were so successful that the Commission has regularly undertaken seeding ever since in mountainous parts of the State.

 

Beginning in Winter 2004, Snowy Hydro Limited is conducting a six-year research project of winter cloud seeding to assess the feasibility of increasing snow precipitation in the Snowy Mountains in Australia. The NSW Natural Resources Commission, responsible for supervising the cloud seeding operations, believes that the trial may have difficulty establishing statistically whether cloud seeding operations are increasing snowfall. This project was discussed at a summit in Narrabri, NSW on 1st December 2006. The summit met with the intention of outlining a proposal for a 5 year trial, focussing on Northern NSW. The various implications of such a widespread trial were discussed, drawing on the combined knowledge of several worldwide experts, including representatives from the Tasmanian Hydro Cloud Seeding Project.

 

At the July 2006 G8 Summit, President Putin commented that air force jets had been deployed to seed incoming clouds so they rained over Finland. However, not much seemed to come of this.[13]

 

In Southeast Asia, open burning produces haze that pollutes the regional environmental. Cloud-seeding has been used to improve the air quality by encouraging rainfall.

 

wiki

[N.O.R.F]

Guess what happened the other day, it rained in the May in Dubai! It rained bucket loads in the middle of the desert!

 

This was no ordanary rain however,,,,,

 

Cloud seeding experiment has thundering success

By Aftab Kazmi, Bureau Chief

Published: May 08, 2008, 00:09

 

Al Ain: Tuesday's thunderstorm in the western and southern parts of the emirates was a result of a cloud seeding (artificial rain) test conducted by the weather authorities.

 

The storm produced intermittent rain in parts of Abu Dhabi and Dubai. It was a surprising phenomenon in the late-spring month of May for the public and some weathermen.

 

An official of the National Centre of Meteorology and Seismology (NCMS) on Wednesday confirmed the centre had carried out cloud seeding tests on clouds that came in from southern Saudi Arabia.

 

Residents and weathermen were baffled by the occurrence of thunderstorms in May.

 

"I was amazed to hear about a thunderstorm," said a weatherman requesting anonymity.

 

He said it was an unusual development of CB clouds, the clouds that generate thunderstorms, as most converge over the UAE in the winter, he added.

 

Abdullah Ahmad Al Mandoos, Executive Director of NCMS, said the cloud seeding test was successful and more experiments would be conducted in the next three months but depending on the weather conditions.

 

The NCMS director said Shaikh Mansour Bin Zayed Al Nahyan, Minister of Presidential Affairs, has played a vital role in the project and has provided a plane and other facilities for its implementation.

 

"He gives continuous guidance," he added.

 

International prize

 

Shaikh Mansour has also encouraged scientists in cloud seeding research and announced an international prize for the best study in the field.

 

"This prize provided immeasurable benefits not only for science but also for many countries in the world," he said.

 

The centre has its own aircraft that is used for sprinkling cloud seeding salts in the moist clouds. The sprinklers are attached to the wings of the aircraft that drop the salt from a certain height on the clouds.

 

The project was started in 2001 by the Department of Atmospheric Studies at the Ministry of Presidential Affairs. The department has now absorbed the UAE Met Department and taken a new identity as NCMS.

 

The implementation of the project was started in cooperation with the National Centre of the Atmospheric Research (NCAR) in the United States, the University of the Witwatersrand, Johannesburg, South Africa, and the National Astronomy Space Agency in the United States NASA, said Al Mandoos.

 

A total of 200 flights were undertaken during the winter and summer of 2001. About half of the flights collected microphysical data in clouds and precipitation, with seeding trials having been performed on about half of those flights. Further studies continued during 2003 and 2004.

 

The studies help NCMS in developing the seeding techniques as per UAE climatic requirements to increase the rainfall, said Al Mandoos. He said the objective of the project is to enhance the national water resources, ground storage, and recycling of freshwater.

 

Research: Solving water problems

 

We dream of being able to modify the weather, especially as pearls of perspiration line brows and march down collars. It may not be such an outlandish idea if one goes by cloud seeding.

 

It is a science that can be used to control winds, suppress hail, dissolve fog or create rain.

 

Scientists have been dabbling in it since 1946, when Dr Vincent J. Shaefer conducted his first field experiments in New York. Today nearly 40 countries are working with it, foremost being China.

 

Rumour has it that not a cloud shall pass over Beijing Olympics opening ceremony. It also plans to use cloud seeding to clear the air pollution problem.

 

Some of the other countries include the United States, UK, Russia, India, Australia, Canada, Algeria, Libya, Morocco, Jordan, Syria, Iraq and Saudi Arabia.

 

It rains because millions of extremely tiny water droplets come together around a nuclei, which could be anything from sand, smoke, salt or dust, to form one big drop of rain.

 

There are two basic forms of rain - warm and cold. Warm rain is from clouds, in tropical regions, with temperatures never colder than 0C. Cold rain happens when the cloud temperatures are lower than 0C.

 

This is the natural process, in case of cloud seeding different types of cloud condensation nuclei are artificially introduced to accelerate the warm rain or cold rain process.

 

However, it can only be done if the cloud system is of the necessary size, with sufficient lifespan and has enough water saturation. Most scientists say it is all about assisting nature.

 

Seeding is done using flares dropped from aircrafts or shot from the ground using artillery or rockets.

 

One of the earliest techniques was the 'static mode' wherein silver iodide or dry ice was introduced into cold clouds. This was followed up by the 'dynamic mode', which had a greater number of silver iodide nuclei being introduced to get more rain.

 

You also have hygroscopic seeding that introduces salt crystals, which function as bigger nuclei to accelerate the warm rain process.

 

As nations look for answers to the problem of water shortage, controlled cloud seeding could be one of the key options.

 

http://www.gulfnews.com/nation/Environment/10211450.html

[Gordon Gekko]

This is highly interesting. I first came across it when I read about a similar experiment being carried out in Portugal last year and couldnt believe it at first. It is most definitely a viable solution to the drought problems, not to mention its inherent ability to improve the farming industry. My only concern is whether or not this sort of 'stimulated rain' include chemicals that can cause environmental problems or any hazardous components as waste-products.

[Gar-haye]

there is always a flip side to tampering with the natural oder of things. will wait the consequences.

[N.O.R.F]

I saw the dark clouds as soon as I left home. Got in the office and it rained heavily but it was over within approx 7 mins.

 

GG, same concerns here. As long as the rain drops don't contain anything which may be detrimental to crops/people I think it should continue. The success rate may be higher in Africa than in the ME as Africa actually has clouds all year round.

[Gordon Gekko]

Northerner did you receive my PM?

[N.O.R.F]

Maya saxib. Resend please.

[Gordon Gekko]

Okay lets try again now, I've had some problems posting PMs here on SOL.

[Khayr]

Ah, pragmatism at its best thanks to scientific engineering.

 

• If the cattle and sheep are costing too much to feed, just feed them dead carcasses

• If the crops are rotting, just inject steriods into them and voila - perfect crops

and now,

• If it ain't raining, then sprinkle some chemicals into the skies and voila - you got rain!

[N.O.R.F]

^^What are you getting at?

[Naden]

Yes, Khayr, scientific engineering is the new kid on the block. If the heavens don't re-certify, they will be deemed redundant and promptly pushed into retirement.

[N.O.R.F]

Khayr, I don't see anything wrong with this.