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Hail Suppression Project

The Soul of Ukraine Foundation, jointly with the Academy of Sciences of Ukraine, presents a ground weather correction technology (hail suppression and precipitation control) of a new generation. The main distinctions between this system and other existing ones are as follows:

  • The efficiency of generated aerosol exceeds the efficiency of the systems currently in use by three orders of magnitude (1,000 times);
  • The generated aerosol is practically not subject to aging and reduction of activity over time;
  • Working solutions do not contain environmentally hazardous components, the content of silver iodide compared with regular systems is significantly reduced;
  • The cost of system operation is minimal compared with the existing rocket artillery and aircraft hail suppression programs, the proposed technology is the safest, compared with them;
  • Significant decrease in the cost of hail suppression efforts allows to extend the hail suppression technology to protection of cheaper crops from hail, which has not been economically viable before;
  • High efficiency of the system allows to count on its usage not only for hail suppression, but also for precipitation control both in winter and in summer.

The above advantages are realized due to fundamental differences in the generated aerosol, while the ice-generating aerosol of conventional generators entirely consists of silver iodide, the aerosol generated by the proposed system essentially consists of chemically and environmentally neutral silicon dioxide modified by silver iodide only on the surface.

The proposed writing is the result of more than 30 years of work by the group of authors in various fields of meteorology, aerosol generation, ice-generating effects of natural and artificial aerosols. Some of the proposed solutions are absolutely new, qualified as know-how.

  1. Summary. Capabilities of the proposed system;
  2. Damage caused by hail. Current state of the problem;
  3. Hail suppression technologies used at the present time;
  4. Characteristics and capabilities of the proposed system;
  5. Other options of usage of the proposed system;
  6. Tasks performed by the group of authors.

1. Summary. Capabilities of the proposed system.

A fully autonomous ground hail suppression system of extremely high efficiency is proposed. Unlike existing systems generating silver iodide (AgI) aerosols, the proposed system generates modified aerosols, most of whose particles consist of silicon dioxide (SiO2), AgI being used in small quantities only for surface modification of SiO2. Thus, much larger and therefore more effective particles are obtained, given minimal use of silver iodide. The generated aerosols also contain large amounts of hygroscopic compounds, which allows to consider them not only as ice-generating, but also as a hygroscopic reagents of high efficiency (impact on warm clouds). The system is characterized by the following differences:

  • Ice-generating activity of the aerosol formed in the temperature bracket from -3оC to -10оC exceeds activity of aerosols of currently existing generators by at least two orders of magnitude;
  • Obtained aerosol does not change its properties when being in the target environment with high relative humidity and the UV radiation for at least five hours. Under the same conditions, the aerosol of traditional generators reduces its ice-generating activity by more than an order of magnitude. Thus, the total efficiency of aerosol, when being in the atmosphere, exceeds the efficiency of aerosol of traditionally used systems by three or more orders of magnitude;
  • Silver iodide content in the working solutions does not go beyond the bracket from 0.5 to 0.8% (4 to 6 g/l);
  • Working solutions contain ammonium iodide, concentration within the range from 5 to 10% (from 40 to 80 g/l);
  • Due to low concentration of silver iodide, the toxicity of used solutions is reduced compared to the conventionally used formulations, and other toxic and environmentally hazardous substances (such as the commonly used dichlorobenzene) are not available in working solutions;
  • The system is completely self-contained and does not require external energy sources, the system operation control is implemented using wireless communication channels.
Thus, the resulting efficiency of the proposed system exceeds that of currently used similar systems by three orders of magnitude, while significantly reducing the silver content in the applied formulations.
Such a large increase in activity, while reducing the concentration of silver compounds, can significantly enhance both the effect of the use of ground weather correction system and significantly increase the area of protected territory.
The system maintenance even with a large number of generators requires minimal physical and human resources.

2. Damage caused by hail. Current state of the problem.

At present, the hail suppression work is carried out in 48 countries of the world (68 hail suppression project), the total area of protected territories exceeding 86 million ha. However, despite the progress in development of hail suppression assets, the total damage from hail keeps significantly rising.


Just for the USA, according to the National Center for Environmental Information, the damage from hail for the observation period 2000 Ц 2015 amounted to:

Total property damage (buildings, structures, industrial sites) $17.447 billion ( $1.163 billion / annum ) or 94% of total damage
Hail-induced damage to agriculture $1.124 billion ( $74.940 billion / annum ) or 6% of total damage
Injuries of varying degree of severity received 305 people ( 20 people / annum )

At that, if in the 15-year period the agricultural damage was tending to decrease in average, the property damage kept rising in average by $50 million a year.

Damage growth dynamics in the USA: 1 Ц property damage, 2 Ц damage to the farm sector.

Also, in 2015, there were 99 hail days, the damage totaled $718.866 million, the property damage occurred on those 99 hail days amounted to $586.009 million. In agricultural areas, hail-days totaled 25, the damage amounted to $ 132.857 million.

Catastrophic hail-storms in the world

Since 2000, there have been damage reaching over $1billion, more than 100 people suffered from injuries and mutilations:
  • April 10, 2001, St. Louis, Missouri, USA Ц damage exceeded $2 billion;
  • July 19, 2002, Henan Province, the People's Republic of China Ц 25 lost, several hundreds injured;
  • June 28Ц29, 2006, Villingen-Schwenningen and suburbs, Baden-Wurttemberg, Germany Ц damage exceeded И150 млн. , more than 100 injured;
  • May 10 & 16, 2010, Oklahoma City, Oklahoma, USA Ц damage $1 billion;
  • April 28, 2012, St. Louis, Missouri, USA - damage $1.6 billion;
  • July 28, 2013, Southern Germany Ц strongest storm for the whole history of Germany; more than И3.5 billion, more than 100 people injured;
  • November 27, 2014, Brisbane, Queensland, Australia Ц damage totaled $1.1 billion, 40 people injured.

Total agricultural losses in the world annually amount to $11 billion, property damage exceeding $100 billion per annum.

It should be noted that at present, the maximum damage in terms of lost value and the number of affected people accounts for cities and industrial centers with high density of population and infrastructure. See below: aircrafts after hail storm:

It is worth noting that in this case the situation is complicated with the fact that at present there is no effective protection of cities and industrial centers.

3. Hail suppression technologies used at the present time.

At the moment, there is only one physically justified method of hail suppression Ц filling the hailstorm cell with an ice-generating aerosol creating additional centers of crystallization. This prevents a further enlarging of individual hailstones Ц instead of large hailstones with high kinetic energy, there will be produced a large number of minute hail-stones, most of which will have time to melt while falling. This method is implemented by the following groups of technologies:

3.1 Rocket Artillery Technology.

Ice-forming aerosol formation occurs directly in the target environment of the cloud. Delivery of the aerosol generator (a cartridge, a shell, an active smoke explosive cartridge) is carried out via launching an anti-hail rocket or via a shot from an artillery system.

Launcher of hail suppression rockets (Russia, Bulgaria, Serbia, Croatia, Macedonia, etc.). Hail suppression rockets Hail suppression artillery launcher (China)

  • Economic efficiency of the technology ~ 90% (carried out thanks to rapid delivery of the ice-generating aerosol directly into the target environment.)

  • High risk of usage. In particular, usage of the method is completely ruled out in the countries with highly developed air traffic (USA, Central Europe);;

  • The most expensive technology is not in use. It requires extensive network of launching pads for missiles, or shooting ranges, each of which protects a very limited area, usually defined by radius of 5 to 8 km (the range of the missile or projectile). In average, even a relatively small hail suppression project employs more than 50 people;

  • Sophisticated logistics (shipping, storage of missiles, security of launching pads, agreeing on shootings with aeronautical services, search and utilization of windy products and so on.);

  • Due to some probability of an abnormal activation of the assets (shells, rockets), this method is completely ruled out above cities, industrial centers, locations of mass building, etc.

As a result, the method cannot be used for hail suppression above the most vulnerable areas, even in the countries where this technology is allowed.

3.2 Hail suppression technology with the use of aircraft.

Hail suppression with the use of aircraft is practically implemented via the following options:

  • Formation of ice-forming aerosol using liquid or pyrotechnic generators placed on board of the aircraft flying along the path of hail clouds movement;

  • Flight of the aircraft over the hail cloud, while shooting squibs flying through the cloud.

Liquid generator installed on the aircraft. Germany, Austria, Croatia and others. Flares with a pyrotechnic ice-generating composition, installed on the aircraft. USA, Argentina, Germany, Austria and others.

  • Economic efficiency of the technology ~ 70% (doable thanks to a relatively short period of time from the aerosol generation till its hitting the cloud area);

  • Using liquid generator is the cheapest technology, which is primarily due to the lack of need for pyrotechnics;

  • Cheaper technology compared with rocket and artillery technology. Several aircrafts can provide hail suppression over significant space, which is unrealistic in the previous case;

  • Despite relatively low efficiency, this is the only way to impact in the event of a hail storm of medium intensity, in situations when the rocket and artillery method is not used (or prohibited by national legislation, or if it concerns protection of industrial or densely populated area).

  • The main drawback of the technology is impossibility to use it in hail storms of considerable intensity, when plane flights are dangerous or impossible. Unfortunately, these are the processes incurring maximum physical damage.

3.3 Ground aerosol-generating systems.

Liquid (solution-burning ice-generating active substances) and pyrotechnic generators are presented. Generators are to be switched on for several hours before a dangerous situation occurs, with the aim of creating a large surface layer containing an ice-generating aerosol. Subsequently, as a result of the impact of rising streams forming hail cloud, aerosol enters the target environment.

Liquid generators are mainly used. Pyrotechnic generators have not received wide acceptance due to variety of price-related and logistical reasons. Ground-based aerosol-generated systems have proliferated in the ground hail suppression projects and in the projects related to precipitation control:

France: Hail suppression project ANELFA USA: Weather Modification Association (Nevada, California, Wyoming, Colorado, South Dacota, North Dacota ...) Canada, Alberta: Ground-Based Cloud Seeding Project
Brazil: Hail suppression project. Spain: Sistema antigranizo al Bajo Aragon Sweden: GIP 2000.

  • Using liquid generators is the cheapest and easiest technology to implement. In case the system is autonomous or maintained by farmers-volunteers, the production personnel may actually be limited to just a few people;

  • Despite low efficiency, this is the only way to impact in the event of hail storms of high intensity, in situations where the rocket and artillery method is not used (or prohibited by national legislation, or if it concerns protection of an industrial or densely populated area).

  • The main disadvantage of the technology is its low efficiency. Thus, despite its fairly widespread use, there is no unequivocal evaluation of it yet. For example, according to ANELFA data, efficiency of the technology in the hail suppression version is about 50% - the lowest result of all possible;

  • There is also a high level of uncertainty in the efficiency of the technology in the mode of increasing precipitations.

3.4 Conclusions.

Given the above material, it can be concluded that:

  • Hail-storms result in the greatest property damage and consequences when localized in cities, urban industrial centers, and areas with developed infrastructure;

  • It is the very situation in which there are no capabilities to efficiently counteract the elemental forces;

  • The situation could be radically changed in case of a significant increase in efficiency of ground fluid generators.

4. Characteristics and capabilities of the proposed system.

The aim of this work and its main result is a significant increase in the efficiency of the ground ice-generating liquid generator (the same principles can be implemented in the design of the aircraft liquid generator):

  • Increase in the efficiency of ice-generating aerosol in the moment of generation;
  • Increase in the stability of ice-generating aerosol and preservation of its properties for longer staying in the target environment;
  • Decrease in silver compounds content in the working solution and decrease in the system operation cost characteristics;
  • A significant increase in the area of protected territory.

4.1 Increase in the efficiency of ice-generating aerosol in the moment of generation.

Since one of the conditions of high efficiency of ice-generating aerosol is its particlesТ size (while maintaining the ice-generating properties), we applied the effect of surface modification of aerosols of the ice-generating neutral substances by silver iodide. A series of chemical compounds were investigated as a base material (oxides of titanium, boron and silicon), and the silica dioxide proved to be the most effective by a number of parameters. The kinetics of SiO2 formation was studied by the source solutions combustion, the composition and concentration of silicone compounds Ц the most promising for the formation of aerosols under consideration Ц were determined. Selected were the solvent systems that ensure the longest-term preservation of working solutions. The optimal ratio of silicon dioxide / silver iodide were identified. All experiments were conducted with the full laboratory version of the ground generator in a horizontal aerodynamic tube.

In the course of the experiments, we demonstrated that by varying the concentration of the organosilicon compounds in the working solution and the velocity of the outer flow blowing around the generator, it is possible to receive aerosols with virtually any breakdown of particles by size. Modal sizes (diameter) may thus vary in any desirable range of the size from 20 to 300 nanometers.

Since the ice-generating efficiency of the aerosol after a certain increase in the content of silver iodide does not increase in the feed solution, there has been defined its marginal effective concentration (from 0.5 to 0.8%). The reason is most likely lies in reaching a complete overlap of SiO2 particlesТ surface with silver iodide.

The temperature dependence of ice-generating activity of aerosols generated by ground-based liquid generators: 1 - classic ground liquid generator (France, Brazil) 1% AgJ, 2 Ц liquid generator (Germany) 6% AgJ, 3 Ц SiO2 aerosol, modified, 0.76 % AgJ, 4 - SiO2 aerosol, modified, 1.52 % AgJ, 5 - SiO2 aerosol, modified, 3.03 % AgJ. Dimension of the axes: х Ц climatic chamber temperature, degrees of Centigrade, у Ц number of active ice-generating nuclei created by 1 gram of the working solution.

Thus, the proposed aerosol formulation comprising a surface-modified SiO2 0.5 - 0.8% AgI has the following advantages with respect to the currently used formulations with high AgI content:

  The threshold of the ice-generating activity of surface-modified aerosol is - 3.5оC instead of -7- 8оC for conventional recipes;
  In the temperature ranges down to - 10оC, the efficiency of aerosol of proposed formulation is superior to conventional formulations by two or more orders of magnitude.

4.2 Changing aerosol activity while staying in the target environment.

An ice-generating aerosol reduces its activity quickly enough, when placed in an environment with high relative humidity, as well as when exposed to UV radiation. This process is most relevant in case of ground generators when a considerable time passes Ц up to several hours Ц before hitting the target environment. The rate of dropping of the ice-generation activity largely depends on the composition of the aerosol particles, and in some cases the difference may reach up to several orders of magnitude. It is also one of the reasons for low efficiency of currently existing ground technologies.

The aerosol of the generator developed by us was tested for change in the activity under conditions close to real conditions of exposure: 90% relative humidity, exposure to UV radiation. Under these conditions, a standard aerosol generator activity decreases by one order of magnitude within three hours. The aerosol activity of the developed generator has remained unchanged during the same period of time.

Studies of changes of ice-generating activity of the aerosol formed during operation of the standard generator (AgJ 1% solution, the generator being in use by French and Brazilian ground projects, the temperature of activity amounting to -14о—). Aerosol of the developed generator: 0.76 % AgJ content (temperature of the ice-generating activity equaling to -10о—). During the experiments, the relative humidity was maintained in the range of 90 - 95%, the dimensions of axles: х Ц aerosol exposure time in the climatic chamber, у Ц number of active ice-generating nuclei with one gram of the solution at this temperature.

  Thus, the total effect of the use of ground generator aerosol of the proposed system reaches three or more orders of magnitude compared to conventional aerosol systems in use.

4.3 Decrease in silver compounds content in the working solution and decrease in the system operation cost characteristics.

In addition to the effects of a significant increase in the aerosol activity, saving of silver compounds is achieved, which is, given the use of ground-based systems scale, remains sufficiently large. Known are the formulations of working solutions of liquid generators, both ground and air, with AgI content 1 to 6%. Given the average number of generators in a ground project amounts to 400 - 500 units, with the working solution usage rate of 1.5 liters per hour and working 30 hours per season, the amount of the working solution burnt within one project totals 22,500 liters, which is 355 kg of AgI, given its concentration being 2% in the working solution. Decrease in silver concentration in the working solution down to 0.76% can result in reduction of AgI use down to 135 kg, or by 62%.

Additional saving of assets and servicing personnelТs labor results from automation of the ground generators systems. In fact, the role of staff is reduced to periodic refueling of the generator capacities with working solutions and replacement of the generatorТs dilapidated parts.

4.4 A significant increase in the area of the protected territory.

Increasing the applied aerosol efficiency, while increasing its life span, will allow to consider the usage of ground-based generators of the system to reduce the effects of hail in much larger territories. As it proceeds from the analysis of statistical data, changes in economic damage in recent years, despite the improvement of the hail suppression technologies, in fact has not shown any positive trends. This suggests that the hail suppression measures being currently applied have a pronounced local nature, and their effect does not tell on macro-economic statistics.

This may be, in particular, due to the intensively undergoing process of the ice-generating aerosolТs aging, which almost completely loses its activity when placed in the environment for a few hours.

Since the proposed system generates an AgI surface-modified SiO2 aerosol, which practically does not age while being in the target environment, the industrial use of the proposed system is possible to reach the hail suppression effect with an impact on a much larger territory.

At the same time, due to lower cost, it is possible to extend the usage of the system in providing hail suppression for cheaper crops whose protection was inexpedient in the past due to economic reasons.

5. Other options of usage of the proposed system.

Along with the hail suppression activities, the proposed generator system can be used in precipitation control Ц with regard to both increase and decrease in it. Increased precipitation is carried out via introducing the calculated quantity of ice-generating aerosol in the target environment, which leads to the destruction of the cloud. The reduction of precipitation occurs at the re-seeding effect in situations when the warm cloud is completely or partially converted into a crystalline state with temporary blocking of the conventional mechanism of precipitation, the latter to be occurring, later along with the cloudТs direction of movement).

The system can be used for raising the water level in reservoirs and hydro complexes, and for reducing the amount of snow in the avalanche-risky mountainous areas, etc.

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