tropical cyclone
A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depen ...
s by flying aircraft into them and
seeding
The term seeding and related terms such as seeded are used in several different contexts:
*Sowing, planting seeds in a place or on an object
*Cloud seeding, manipulating cloud formations
*Seeding (computing), a concept in computing and peer-to-pee ...
with silver iodide. The project was run by the United States Government from 1962 to 1983. The hypothesis was that the silver iodide would cause supercooled water in the storm to freeze, disrupting the inner structure of the hurricane, and this led to seeding several Atlantic hurricanes. However, it was later shown that this hypothesis was incorrect. It was determined that most hurricanes do not contain enough supercooled water for cloud seeding to be effective. Additionally, researchers found that unseeded hurricanes often undergo the same structural changes that were expected from seeded hurricanes. This finding called Stormfury's successes into question, as the changes reported now had a natural explanation.
The last experimental flight was flown in 1971, due to a lack of candidate storms and a changeover in NOAA's fleet. Project Stormfury was officially canceled more than a decade after the last modification experiment. Although the project failed to achieve its goal of reducing the destructiveness of hurricanes, its observational data and storm lifecycle research helped improve meteorologists' ability to forecast the movement and intensity of hurricanes.
Hypothesis
Cloud seeding was first attempted by
Vincent Schaefer
Vincent Joseph Schaefer (July 4, 1906 – July 25, 1993) was an American chemist and meteorologist who developed cloud seeding. On November 13, 1946, while a researcher at the General Electric Research Laboratory, Schaefer modified clouds in the B ...
and Irving Langmuir. After witnessing the artificial creation of ice crystals, Langmuir became an enthusiastic proponent of
weather modification
Weather modification is the act of intentionally manipulating or altering the weather. The most common form of weather modification is cloud seeding, which increases rain or snow, usually for the purpose of increasing the local water supply. W ...
.Davies p 85 Schaefer found that when he dumped crushed
dry ice
Dry ice is the solid form of carbon dioxide. It is commonly used for temporary refrigeration as CO2 does not have a liquid state at normal atmospheric pressure and sublimates directly from the solid state to the gas state. It is used primarily ...
into a cloud, precipitation in the form of
snow
Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes.
It consists of frozen crystalline water throughout ...
resulted.Whipple p. 150
With regard to hurricanes, it was hypothesized that by seeding the area around the
eyewall
The eye is a region of mostly calm weather at the center of tropical cyclones. The eye of a storm is a roughly circular area, typically in diameter. It is surrounded by the ''eyewall'', a ring of towering thunderstorms where the most severe weat ...
latent heat
Latent heat (also known as latent energy or heat of transformation) is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process — usually a first-order phase transition.
Latent heat can be underst ...
would be released. This would promote the formation of a new eyewall. As this new eyewall was larger than the old eyewall, the winds of the tropical cyclone would be weaker due to a reduced
pressure gradient
In atmospheric science, the pressure gradient (typically of air but more generally of any fluid) is a physical quantity that describes in which direction and at what rate the pressure increases the most rapidly around a particular location. The p ...
.Landsea D9 Even a small reduction in the speed of a hurricane's winds would be beneficial: since the damage potential of a hurricane increased as the square of the wind speed,Landsea D5 a slight lowering of wind speed would have a large reduction in destructiveness.
Due to Langmuir's efforts, and the research of Schaefer at
General Electric
General Electric Company (GE) is an American multinational conglomerate founded in 1892, and incorporated in New York state and headquartered in Boston. The company operated in sectors including healthcare, aviation, power, renewable en ...
, the concept of using cloud seeding to weaken hurricanes gathered momentum. Indeed, Schaefer had caused a major snowstorm on December 20, 1946 by seeding a cloud. This caused GE to drop out for legal reasons. Schaefer and Langmuir assisted the U.S. military as advisors for Project Cirrus, the first large study of
cloud physics
Cloud physics is the study of the physical processes that lead to the formation, growth and precipitation of atmospheric clouds. These aerosols are found in the troposphere, stratosphere, and mesosphere, which collectively make up the greatest p ...
and
weather modification
Weather modification is the act of intentionally manipulating or altering the weather. The most common form of weather modification is cloud seeding, which increases rain or snow, usually for the purpose of increasing the local water supply. W ...
. Its most important goal was to try to weaken
hurricanes
A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depend ...
.Whipple p 151
Project Cirrus
Project Cirrus was the first attempt to modify a hurricane. It was a collaboration of the
General Electric
General Electric Company (GE) is an American multinational conglomerate founded in 1892, and incorporated in New York state and headquartered in Boston. The company operated in sectors including healthcare, aviation, power, renewable en ...
Corporation, the
US Army Signal Corps
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, colors = Orange and white
, colors_label = Corps colors
, march =
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US Air Force
The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Sig ...
. After several preparations and initial skepticism by government scientists,Willoughby, Jorgensen, Black, and Rosenthal p 505 the first attempt to modify a hurricane began on October 13, 1947 on a
hurricane
A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depend ...
that was heading west to east and out to sea.
The project's two
B-17
The Boeing B-17 Flying Fortress is a four-engined heavy bomber developed in the 1930s for the United States Army Air Corps (USAAC). Relatively fast and high-flying for a bomber of its era, the B-17 was used primarily in the European Theater ...
and a B-29 of the 53rd Weather Reconnaissance group were dispatched from MacDill Field, Florida, to intercept the hurricane.Havens p. 61 The seeding B-17 flew along the rainbands of the hurricane, and dropped nearly 180 pounds (82 kilograms) of crushed
dry ice
Dry ice is the solid form of carbon dioxide. It is commonly used for temporary refrigeration as CO2 does not have a liquid state at normal atmospheric pressure and sublimates directly from the solid state to the gas state. It is used primarily ...
into the clouds. The crew reported "Pronounced modification of the cloud deck seeded". It is not known if that was due to the seeding. Next, the hurricane changed direction and made landfall near
Savannah, Georgia
Savannah ( ) is the oldest city in the U.S. state of Georgia and is the county seat of Chatham County. Established in 1733 on the Savannah River, the city of Savannah became the British colonial capital of the Province of Georgia and later t ...
. The public blamed the seeding, and Irving Langmuir claimed that the reversal had been caused by human intervention. Cirrus was canceled, and lawsuits were threatened. Only the fact that a system in 1906 had taken a similar path, as well as evidence showing that the storm had already begun to turn when seeding began, ended the litigation. This disaster set back the cause of seeding hurricanes for eleven years.
At first the seeding was officially denied and it took years before the government admitted it. According to the Sept. 12, 1965 edition of the Fort Lauderdale News and Sun-Sentinel, in 1947 a hurricane "went whacky" and "Twelve years later it was admitted the storm ''had in fact been seeded.''"
Between the projects
The
United States Weather Bureau
The National Weather Service (NWS) is an agency of the United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weather-related products to organizations and the public for the ...
's
National Hurricane Research Project
The National Hurricane Research Project (NHRP) was initiated in 1955 by the United States Weather Bureau in response to the devastating 1954 hurricane season, which saw hurricanes ''Carol'', ''Edna'', and ''Hazel'' bring destruction and floodin ...
, founded in 1955, had as one of its objectives to investigate the scientific validity of hurricane modification methods. To this end, silver iodide dispensers were tested in Hurricane Daisy in August 1958. The flares were deployed outside of the hurricane eyewall, so this was an equipment test rather than a modification experiment. The equipment malfunctioned in all but one of the flights, and no conclusive data was acquired.
The first seeding experiment since the Cirrus disaster was attempted on September 16, 1961, into
Hurricane Esther
Hurricane Esther was the first large tropical cyclone to be discovered by satellite imagery. The fifth tropical cyclone, named storm, and hurricane of the 1961 Atlantic hurricane season, Esther developed from an area of disturbed weather hundreds ...
by NHRP and the
United States Navy
The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...
aircraft. Eight cylinders of silver iodide were dropped into Esther's eyewall, and winds were recorded as weakening by 10 percent.Davies p 89 The next day, more seeding flights were made. This time, the silver iodide did not fall into the eyewall, and no reduction in windspeed was observed. These two results were interpreted as making the experiment a "success".Davies p 90
The seedings into Hurricane Esther led to the establishment of Project Stormfury in 1962. Project Stormfury was a joint venture of the
United States Department of Commerce
The United States Department of Commerce is an executive department of the U.S. federal government concerned with creating the conditions for economic growth and opportunity. Among its tasks are gathering economic and demographic data for bus ...
and the
United States Navy
The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...
.
Project BATON
The objective of Project BATON was the analysis of the life history of thunderstorms. A Department of
Defense research activity supported by the Advanced Research Project Agency, Project BATON sought to expand understanding of storm physics as an aid to weather forecasting, fire prevention, and, possibly, for artificially controlling the weather. Dr. Helmut Weickmann, as an employee of the U.S, Army Signal Research and Development Laboratory, and Dr. Paul MacCready of Meteorology Research, Inc., were joint leaders of the Project BATON team.
During the 1962 July–August storm season in Flagstaff, Arizona, the scientists, selected "guinea pig" storms, and seeded them with chemicals. Effects were thoroughly analyzed from the ground and from the air with time-lapse motion picture cameras, stereo still cameras, storm radar, lightning detectors, and airborne heat sensors. Among the agents inserted in selected clouds were "condensation nuclei" which temporarily increased the number of water droplets in the cloud, and pulverized dry ice, which turns a portion of the cloud to fine snow crystals that remain aloft. The utilization of these agents facilitated study of a storm's characteristics.
Project STORMFURY begins
Robert Simpson became its first director, serving in this capacity until 1965. There were several guidelines used in selecting which storms to seed. The hurricane had to have a less than 10 percent chance of approaching inhabited land within a day;Whipple p 153 it had to be within range of the seeding aircraft; and it had to be a fairly intense storm with a well-formed eye. The primary effect of these criteria was to make possible seeding targets extremely rare.Whipple p 154
No suitable storms formed in the 1962 season. Next year, Stormfury began by conducting
experiments
An experiment is a procedure carried out to support or refute a hypothesis, or determine the efficacy or likelihood of something previously untried. Experiments provide insight into cause-and-effect by demonstrating what outcome occurs when ...
on cumulus clouds. From August 17 to 20 of that year, experiments were conducted in 11 clouds, of which six were seeded and five were controls. In five of the six seeded clouds, changes consistent with the working hypothesis were observed.Willoughby, Jorgensen, Black, and Rosenthal p 507
On August 23, 1963,
Hurricane Beulah
Hurricane Beulah was the second tropical storm, second hurricane, and only major hurricane during the 1967 Atlantic hurricane season. It tracked through the Caribbean, struck the Yucatán Peninsula of Mexico as a major hurricane, and moved west- ...
was the site of the next seeding attempt. It had an indistinct eyewall. In addition, mistakes were made, as the seedings of silver iodide were dropped in the wrong places. As a consequence, nothing happened. The next day, another attempt was made, and the seeders hit their targets. The eyewall was observed to fall apart and be replaced by another eyewall with a larger radius. The sustained winds also fell by twenty percent. All in all, the results of the experiments on Beulah were "encouraging but inconclusive."R. Cecil Gentry, quoted in Davies p 90
In the six years after Beulah, no seedings were conducted for several different reasons. In 1964, measurement and observation equipment was not ready to be used. The year after that, all flights were used for additional experimentation in non-hurricane clouds.
Joanne Simpson
Joanne Simpson (formerly Joanne Malkus, born Joanne Gerould; March 23, 1923 – March 4, 2010) was the first woman in the United States to receive a Ph.D. in meteorology, which she received in 1949 from the University of Chicago.Atlas D and Lemone ...
became its director beginning in 1965.
While out to sea in August of the
1965 Atlantic hurricane season
The 1965 Atlantic hurricane season was the first to use the modern-day bounds for an Atlantic hurricane season, which are June 1 to November 30. These dates conventionally delimit the period of each year when most tropical cyclones form ...
, Stormfury meteorologists decided that Hurricane Betsy was a good candidate for seeding.Whipple p 153 However, the storm immediately swung towards land, and on September 1, the planned flights were canceled. For some reason, the press was not notified that there were no seedings, and several newspapers reported that it had begun. As Betsy passed close to
the Bahamas
The Bahamas (), officially the Commonwealth of The Bahamas, is an island country within the Lucayan Archipelago of the West Indies in the North Atlantic. It takes up 97% of the Lucayan Archipelago's land area and is home to 88% of the ar ...
and smashed into southern
Florida
Florida is a state located in the Southeastern region of the United States. Florida is bordered to the west by the Gulf of Mexico, to the northwest by Alabama, to the north by Georgia, to the east by the Bahamas and Atlantic Ocean, and to ...
, the public and
Congress
A congress is a formal meeting of the representatives of different countries, constituent states, organizations, trade unions, political parties, or other groups. The term originated in Late Middle English to denote an encounter (meeting of ...
thought that seeding was underway and blamed Stormfury. It took two months for Stormfury officials to convince Congress that Betsy was not seeded, and the project was allowed to continue. A second candidate,
Hurricane Elena
Hurricane Elena was a tropical cyclone that affected eastern and central portions of the United States Gulf Coast in late August and early September 1985. Threatening popular tourist destinations during Labor Day weekend, Elena repeatedly de ...
, stayed too far out to sea.
After Betsy, two other hurricanes came close to being seeded.
Hurricane Faith
Hurricane Faith was a long-lived Cape Verde hurricane and was the sixth named storm and fifth hurricane of the 1966 Atlantic hurricane season. Faith developed from an area of disturbed weather between Cape Verde and the west coast of Africa on A ...
was considered a likely candidate, but it stayed out of range of the seeding planes. That same year, recon flights were conducted into
Hurricane Inez
Hurricane Inez was a powerful major hurricane that affected the Caribbean, Bahamas, Florida, and Mexico in 1966. It was the first storm on record to affect all of those areas. It originated from a tropical wave over Africa, and became a tropical ...
, but there were no seedings. Both the
1967
Events
January
* January 1 – Canada begins a year-long celebration of the 100th anniversary of Confederation, featuring the Expo 67 World's Fair.
* January 5
** Spain and Romania sign an agreement in Paris, establishing full consular and ...
and 1968 seasons were inactive. Because of that, there were no suitable seeding targets in either of those two seasons.
Dr. R. Cecil Gentry became the director of Stormfury in 1968. There were no more near-seedings until 1969. In the interim, equipment was improved. What once was the primitive method of hand-dumping dry ice was replaced with rocket canisters loaded with silver iodide, and then gun-like devices mounted on the wings of the airplanes that fired silver iodide into the clouds. Observation equipment was improved. Additional reconnaissance data was utilized to modify the working hypothesis. The new theory took cumulus towers outside the
eyewall
The eye is a region of mostly calm weather at the center of tropical cyclones. The eye of a storm is a roughly circular area, typically in diameter. It is surrounded by the ''eyewall'', a ring of towering thunderstorms where the most severe weat ...
into account. According to the revised theory, by seeding the towers,
latent heat
Latent heat (also known as latent energy or heat of transformation) is energy released or absorbed, by a body or a thermodynamic system, during a constant-temperature process — usually a first-order phase transition.
Latent heat can be underst ...
would be released. This would trigger the start of new convection, which would then cause a new eyewall. Since the new eyewall was outside the original one, the first eyewall would be choked of energy and fall apart. In addition, since the new eyewall was broader than the old one, the winds would be lower due to a less sharp pressure difference.Hurricane Debbie in 1969 provided the best opportunity to test the underpinnings of Project Stormfury. In many ways it was the perfect storm for seeding: it did not threaten any land; it passed within range of seeding aircraft; and was intense with a distinct eye.Whipple p 153-54 On August 18 and again on August 20, thirteen planes flew out to the storm to monitor and seed it. On the first day, windspeeds fell by 31%. On the second day, windspeeds fell by 18%. Both changes were consistent with Stormfury's working hypothesis. Indeed, the results were so encouraging that "a greatly expanded research program was planned."Gentry, quoted in Davies p 91 Among other conclusions was the need for frequent seeding at close to hourly intervals.Black, Senn, and Courtright p 216
The
1970
Events
January
* January 1 – Unix time epoch reached at 00:00:00 UTC.
* January 5 – The 7.1 Tonghai earthquake shakes Tonghai County, Yunnan province, China, with a maximum Mercalli intensity of X (''Extreme''). Between 10,000 and ...
and 1971 seasons provided no suitable seeding candidates. Despite this, flights were conducted into Hurricane Ginger. Ginger was not a suitable storm for seeding, due to its diffuse, indistinct nature. The seeding had no effect. Ginger was the last seeding done by Project Stormfury.
After the seedings
Atlantic hurricanes meeting all of the criteria were extremely rare, which made duplication of the "success" reached with Hurricane Debbie extremely difficult. Meanwhile, developments outside of meteorology hindered the cause of hurricane modification.
In the early 1970s, the Navy withdrew from the project.Davies p 91 Stormfury began to refocus its efforts on understanding, rather than modifying, tropical cyclones.Williams At the same time, the Project's B-17s were nearing the end of their operational lifetimes. At the cost of $30 million (year unknown) two
Lockheed P-3
The Lockheed P-3 Orion is a four-engined, turboprop anti-submarine and maritime surveillance aircraft developed for the United States Navy and introduced in the 1960s. Lockheed based it on the L-188 Electra commercial airliner. This action required many of the same safety requirements as in the Atlantic, but had the advantage of a much higher number of potential subjects.
The plan was to begin again in 1976, and seed typhoons by flying out of
Guam
Guam (; ch, Guåhan ) is an organized, unincorporated territory of the United States in the Micronesia subregion of the western Pacific Ocean. It is the westernmost point and territory of the United States (reckoned from the geographic cent ...
. However, political issues blocked the plan. The
People's Republic of China
China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...
announced that it would not be happy if a seeded typhoon changed course and made landfall on its shores, while Japan declared itself willing to put up with difficulties caused by typhoons because that country got more than half of its rainfall from tropical cyclones.
Similar plans to operate Stormfury in the eastern north Pacific or in the Australian region also collapsed.Willoughby, Jorgensen, Black, and Rosenthal p 508
Failure of the working hypothesis
Multiple eyewalls had been detected in very strong hurricanes before, including Typhoon SarahBlack, Senn, and Courtright p 210 and
Hurricane Donna
Hurricane Donna, known in Puerto Rico as Hurricane San Lorenzo, was the strongest hurricane of the 1960 Atlantic hurricane season, and caused severe damage to the Lesser Antilles, the Greater Antilles, and the East Coast of the United States, e ...
.Jordan and Schatzle pp 354-56 Double eyewalls were usually only seen in very intense systems. They had also been observed post-seeding in some of the seeded storms. At the time, the only observations of rapid changes in eyewall diameter, other than during presumably successful seedings, occurred during rapid changes in storm intensity.Black, Senn, and Courtright p 213 It remained unclear whether the seedings caused the secondary eyewalls or whether it was just part of a natural cycleWilloughby, Clos, and Shorebah p 396 (because correlation does not imply causation). It was initially thought that eyewall changes similar to those observed in seeded but not unseeded systems provided the evidence that Project Stormfury was a success. But if it was later observed that such eyewall changes were common in unseeded systems as well, such observations would throw doubt on the hypothesis and assumptions driving Project Stormfury.Willoughby, Jorgensen, Black, and Rosenthal p 511
Data and observations did in fact begin to accumulate that debunked Stormfury's working hypothesis. Beginning with Hurricanes Anita and
David
David (; , "beloved one") (traditional spelling), , ''Dāwūd''; grc-koi, Δαυΐδ, Dauíd; la, Davidus, David; gez , ዳዊት, ''Dawit''; xcl, Դաւիթ, ''Dawitʿ''; cu, Давíдъ, ''Davidŭ''; possibly meaning "beloved one". w ...
, flights by hurricane hunting aircraft encountered events similar to what happened in "successfully" seeded storms. Anita itself had a weak example of a concentric eyewall cycle, and David a more dramatic one. In August 1980, Hurricane Allen passed through the
Atlantic
The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe an ...
Gulf of Mexico
The Gulf of Mexico ( es, Golfo de México) is an ocean basin and a marginal sea of the Atlantic Ocean, largely surrounded by the North American continent. It is bounded on the northeast, north and northwest by the Gulf Coast of the United ...
. It also underwent changes in the diameter of its eye and developed multiple eyewalls. All this was consistent with the behavior that would have been expected of Allen had it been seeded. Thus, what Stormfury thought to have accomplished by seeding was also happening on its own.Goldenberg
Other observations in Hurricanes Anita, David, Frederic, and AllenWilloughby, Jorgensen, Black, and Rosenthal p 509 also discovered that tropical cyclones have very little supercooled water and a great deal of ice crystals.Hurricane Research Division The reason that tropical cyclones have little supercooled water is that the
updraft
In meteorology, an updraft is a small-scale current of rising air, often within a cloud.
Overview
Localized regions of warm or cool air will exhibit vertical movement. A mass of warm air will typically be less dense than the surrounding regi ...
s within such a system are too weak to prevent water from either falling as rain or freezing.Landsea C4 As cloud seeding needed supercooled water to function, the lack of supercooled water meant that seeding would have no effect.
Those observations called the basis for Project Stormfury into question. In the middle of 1983, Stormfury was finally canceled after the hypothesis guiding its efforts was invalidated.Willoughby, Jorgensen, Black, and Rosenthal p 513
Legacy
In the sense of weakening hurricanes to reduce their destructiveness, Project Stormfury was a complete failure because it did not distinguish between natural phenomena in tropical cyclones and the impact of human intervention. Millions of dollars had been spent. In the end, " rojectSTORMFURY had two fatal flaws: it was neither microphysically nor statistically feasible."
In addition, Stormfury had been a primary generator of funding for the
Hurricane Research Division The Hurricane Research Division (HRD) is a section of the Atlantic Oceanographic and Meteorological Laboratory (AOML) in Miami, Florida, and is the U.S. National Oceanic and Atmospheric Administration's (NOAA) focus for tropical cyclone research. T ...
. While the project was operational, the HRD's budget had been around $4 million (1975
USD
The United States dollar (symbol: $; code: USD; also abbreviated US$ or U.S. Dollar, to distinguish it from other dollar-denominated currencies; referred to as the dollar, U.S. dollar, American dollar, or colloquially buck) is the official ...
; $16 million 2008 USD), with a staff of approximately 100 people.Davies p 92 In 2000, the HRD employed 30 people and has a budget of roughly $2.6 million each year.Davies p 93
However, Project Stormfury had positive results as well. Knowledge gained during flights proved invaluable in debunking its hypotheses. Other science resulted in a greater understanding of tropical cyclones. In addition, the Lockheed P-3's were perfectly suitable for gathering data on tropical cyclones, allowing improved forecasting of these monstrous storms. Those planes were still used by the NOAA as of 2005.Swanson and Williams
Former
Cuba
Cuba ( , ), officially the Republic of Cuba ( es, República de Cuba, links=no ), is an island country comprising the island of Cuba, as well as Isla de la Juventud and several minor archipelagos. Cuba is located where the northern Caribbea ...
n president Fidel Castro alleged that Project Stormfury was an attempt to weaponize hurricanes.
See also
*
Operation Popeye
Operation Sober Popeye (Project Controlled Weather Popeye / Motorpool / Intermediary-Compatriot) was a military cloud-seeding project carried out by the U.S. Air Force during the Vietnam War in 1967–1972. The highly classified program attempted ...
*
Weather modification in North America Weather modification in North America has been taking place since at least the 1950s. Programs related to this field have been authorized by the governments of both the United States and Canada.
Alberta Hail Project
The Alberta Hail Project was ...