One of the technological developments in meteorology is weather modification or cloud seeding. This phrase is used to refer to a deliberate treatment of some types of clouds or cloud systems with the aim of affecting the process of precipitation within those clouds. In order to attain this, substances are dispersed from ground generators or planes into the air to act as ice nuclei or cloud condensers. Their function is to change the microphysical process within the mass of cloud. This technology is gaining a widespread application globally and its practical uses are fog removal, lighting suppression, causing precipitation in form of rainfall, preventing hailstorms and hurricane control. Despite the increasing application, there are questions that have been raised relating to the technology and its practical uses, especially in regard to its effectiveness. The aim of this paper is to address such questions by analyzing the effectiveness of cloud seeding.
Application of Cloud Seeding
In China, during the period preceding the Olympics festivals, cloud seeding was used to cause rain and snow. This technology was specifically applied in Northern China and was successful to the extent that in snowed for the first time in Hebei, around Beijing (Moseman, 2009). The Chinese capital had not witnessed any precipitation before this from the previous October. The precipitation formed as a result of cloud seeding was significant and caused at least the closure of 12 area highways in or near Beijing. Cloud seeding in this case saved China from the pangs of the worst drought in the country’s history in the last few decades. The seeding of clouds by the Chinese government to cause the snowstorm involved the use of over 40 sticks of silver iodide, each the size of a cigarette stick Beijing (Moseman, 2009). China plans to use cloud seeding to produce over 1.7trillion feet cubed of precipitation annually through the application of the technology.
Fog Removal and Lighting Suppression
Cloud seeding is effective in the removal of fog in order to achieve visibility improvement. Fog dispersal is accomplished when some substances are sprayed into the atmosphere of the area covered by fog. These substances act as nuclei around which the tiny water droplets condense. In this way, they will no longer be distributed all over the atmosphere as tiny droplets but regroup into few big droplets. Fog removal is important especially where high visibility is paramount such as in airports. Studies have indicated the high level of effectiveness of cloud seeding in removing fog and clouds from affected areas (Ryan & King, 1997). The technology is effective in a few square miles and often in a matter of hours.
Lightning suppression has a high economic value to both humans and the environment. Lightening can cause death and sometimes leads to the ignition of forest fires. When thunderheads are seeded with tiny aluminium fibers, they tend to dissipate some of their electrical charges in the cloud. Very little research on the effectiveness of this process in lightning suppression was performed. Nevertheless, the little work that has been carried out to date has shown promising results (Ryan & King, 1997).
Cloud Seeding and Rain Production
Rain is an important factor in the production of plant crops and during the rearing of animals. This is because rain is, in most cases, the main source of water in many areas. Even without considering agricultural productivity, rain is useful in that it helps in the regulation of temperatures and in containing dust and improving humidity. In fact, in desert areas such as the California’s Mojave Desert, it is a rare resource, its preciousness far beyond measure. Essentially, cloud seeding has been applied in many jurisdictions as a water management strategy, in many cases the technology being applied with an aim of causing rain. This is done by distributing chemical substances in the clouds, one common substance used in this respect being dry ice.
The effectiveness of cloud seeding in producing rain has been subject to a lot of debate. While in many places, it has been applied; its effectiveness in all cases still remains under debate. Several studies in Texas have shown that cloud seeding results in increased rainfall. One such study which involved several programs was conducted in Texas USA. One of the programs that targeted an area of 3600square miles was initiated in 1971, the oldest among the Texas programs. In the long term, the results of the program showed that there was a 34% rise in the normal historic precipitation after the application of cloud computing (Edwards Aquifer, nd). Yet another program initiated in 1986, the Southwest Cooperative Program targeting an area of 5000 square miles also showed an increase in precipitation levels. Between1986 and1994, a total of 93 seeding operations were conducted and the results of these compared to those of 90 non-seeded storm cells (Edwards Aquifer, nd). In comparison with the non-seeded cells, the clouds that underwent seeding had a 7% height increase, and the area covered by the precipitation increased by just over 42% (Edwards Aquifer, nd). Yet again, the time taken by the storm increased by about 35% even as the precipitation volume rose by 130% (Edwards Aquifer, nd).
A group of researchers from the Monash University, in collaboration with renewable energy company called Hydro Tasmania, conducted an extensive monthly analysis on the patterns of rainfall over the hydroelectric catchment region between May and October beginning 1960 until 2005. The group investigators select clouds to be treated using a special and more reliable weather radar technology that enabled them to observe all the tiny processes occurring within them. At the end of the study, Steven Siems, the leader of the study, confessed that for the first time, an independent analysis data on cloud seeding has indicated statistically significant increase in the amounts of rainfall (Macfarlane, 2009). The analysis conducted by the group revealed that high rainfall amounts were recorded in the parts of the catchment where cloud seeding was used than in those regions where the technology was not used. A number of statistical tests done independently indicated a consistent increase of at least 5% in monthly rainfall over selected the catchment area.
The American Meteorological Society in its capacity as a reliable and authoritative organization holds that cloud seeding leads to an increase of 10% in precipitation levels. This is based on statistical evidence gathered from various studies. However, the organization is quick to add that there is no conclusive evidence on the cause-effect relationship in regard to cloud seeding. Several independent studies have shown that an increase of at least 5% in monthly precipitation in Tasmania (Ryan & King, 1997).
One organization that has trashed the effectiveness of cloud seeding in the production of rain is the National Academy of Sciences. In its view, the organization states that the three decades of studies conducted on cloud seeding have not produced convincing evidence that the technology works and is indeed reliable. A group of researchers have claimed that cloud seeding is not effective in yielding rainfall as once thought. This group of researchers conducted their studies in target region over the Sea of Galilee, north of the nation of Israel. This team of researchers conducted a comprehensive reassessment of the effects of this technology over the past fifty years. They used a comprehensive rainfall database and with this, they made statistical comparison of periods of cloud seeding and periods where it was not done, as well as the amounts of precipitation in adjacent regions where cloud seeding was not done (Levin et al 2010).
This group claimed that rainfall increases was exclusively an effect of change in weather patterns and not cloud seeding and therefore they happen by chances. They stated that the initial increase of rainfall in a 6-year period in the area of study was a response to a type of cyclones which showed consistency for the 6 years. It therefore affected the seeded and the adjacent unseeded areas equally. However, Pinhas Alpert, one of the researchers agreed on the influence of cloud seeding in forming and increasing rainfall. He stated that the only place where cloud seeding could possibly be successful is when seeding is done on orographic clouds that form over Alpert mountains and are short-lived. He states that in this type of cloud, cloud seeding could function to increase the rate of the formation of precipitation (Levin et al 2010). Although this report does not strongly affirm the powerful effects of cloud seeding in causing precipitation, it is already a proof that cloud seeding can stimulate the formation. This acceleration of cloud formation will eventually result in increased amounts of rainfall by increasing the frequency of rainfall or by attracting formation of thicker clouds.
Countries such as South Africa, Thailand, Russia and Israel among numerous other nations have tried to use cloud seeding to produce rain or prevent hailstorms. The results of these studies have been significantly different from one another. Researchers in Australia discovered that different locations respond differently to the technology. In Tasmania for example, static cloud seeding was very effective, this not being the case in Australia’s plains (Ryan & King, 1997).
It is for a fact that cloud seeding is extremely expensive a venture although not as much as diverting river channels or constructing new canals. China as a country spends between 60 and 90 million US dollars annually in cloud seeding. Between 1995 and 2003, the nation has spent in excess of 265 million US dollars in cloud seeding activities. Beyond the costs associated with cloud seeding, the safety of the environment has been cited as one concern (Howell, 1977). Questions of the toxicity of silver iodide and its propensity to cause soil contamination have formed part of the debate in the effectiveness of cloud seeding.
Hail and Hurricane Control
Cloud seeding has been applied in the prevention of hailstorms in many countries. Cloud seeding is also fairly effective in preventing or at least controlling hailstorms. In this situation, large amounts of chemical substances are dispersed into the atmosphere of the region expected to experience hailstorms. The intention of such actions is to prevent the formation of precipitation. This is called over seeding. During the period of 2008 Olympics, this process was conducted in Beijing and it was effective in limiting the amount of rainfall during the Olympic period. The same could therefore be applied to a great extend to limit the formation of hailstorms (Levin et al, 2010).
The principle that underlies hail suppression studies is that hail can prevention can occur if the atmosphere is saturated with nuclei upon which moisture can condense and solidify. Essentially, the technology is done to reduce the size of hailstones that fall thereby preventing damage to crops. Hail suppression according to certain quarters has been noted to increase by between 20 and 50 percent reduction following the application of cloud seeding. However, many researchers agree that results from research conducted on hail suppression have been far from encouraging.
Hurricane control is an activity that would accrue significant economic benefit to humans. Cloud computing has been suggested as one strategy for dissipating the energy that hurricanes store. Researchers have proposed the seeding of the high speedy winds that surround the hurricane and its eye. Research conducted on several hurricanes including Ester (1961) Beulah (1963) and Debbie (1969) have revealed that seeding can reduce the hurricane winds by up to thirty percent.
Very little research has so far been conducted on the subject of cloud seeding in relations to hail suppression and hurricane control. While some studies indicate positive results in regard to hail suppression, a great majority of researchers are of the view that that the results are far from satisfactory. In this respect, the effectiveness of hail suppression using cloud seeding is still questionable. Similarly, a lot of conclusive research is yet to be conducted to establish the effectiveness of the technology in hurricane control. While the results are so far promising in terms of speed reduction, the costs and environmental impacts associated with the venture degrade the effectiveness of the method (Howell, 1977).
Emerging Trends and Future of Cloud Seeding Technologies
Cloud seeding has been in practiced in a number of countries for the last 40 years. With so much yet to be established in regard to the technology, the future of cloud seeding today is quite unclear. The efficiency of the technology is especially difficult to predict especially considering that different storm systems behave differently and are therefore affected to varied levels by cloud seeding. It order for cloud seeding to be effective in the case of hurricane control for example, a compound that can expand between 10 and 20 times and cool simultaneously is needed. So far, it has been established that such substances exist in hurricane rains thereby making the introduction of more particles quite insignificant.
During cloud seeding of hurricanes, at most three planes manned by civilians are always used, they being several miles apart from one another. This is done especially considering the high risks associated with the hurricanes. In the future, governments could deploy airforce personnel to perform the activity while using awips planes which in turn manipulate the planes.
While in the past cloud seeding has been done using planes, there is a high chance that the activity will be performed in future using yachts. A study conducted by specialists from the University of Edinburgh and the University of Manchester have managed to design cloud seeding yachts. The yachts which are designed to be powered by wind will spray salty water from the sea into the atmosphere so as to raise the clouds’ reflectivity. With this done, the clouds will reflect more of the solar energy into space (TFOT, Nd). It is estimated that only 3% of this cloud reflectivity would counter global warming to the full. It is estimated that at least 50 boats in the form of cloud seeders would have to be used to counter the global phenomenon (TFOT, Nd).
Several studies have been done through operations projects and many articles have been published by researchers. Although some of them nullify the efficiency of cloud seeding to increase rainfall, majority of agree to it. On average, the figures for the various projects indicate a 5% -30% increase in the amounts of rainfall when seeding is conducted over a given region. Cloud seeding-induced precipitation is even higher during the warm seasons and this increase could even be as high as 100%. Cloud seeding has also proved to be effective in lightning suppression, fog dispersion and hurricane control, albeit with few references.
- Edwards Aquifer (nd) Cloud Seeding. Retrieved 8th December, 2011. http://www.edwardsaquifer.net/cloudseeding.html
- Howell, W. (1977) “Environmental Impacts of Precipitation Management: Results and Inferences from Project Skywater”. Bull. American Meteorological Society, 58, 488–501
- Levin, Z. Halfon, N. and Alpert, A. (2010). “Reassessment of rain enhancement experiments and operations in Israel including synoptic considerations.” Atmospheric Research. (4) pp 513
- Macfarlane, M. (2009). Major study proves cloud seeding effective. Retrieved 8th December, 2011. http://www.cosmosmagazine.com/news/2514/major-study-proves-cloud-seeding-effective?page=0%2C0.
- Moseman A. (2009) Does cloud seeding work? Retrieved 8th December, 2011. http://www.scientificamerican.com/article.cfm?id=cloud-seeding-china-snow
- North American Weather Consultants (2005). Cloud Seeding Frequently Asked Questions. Retrieved 8th December, 2011. http://www.nawcinc.com/wmfaq.html
- Ryan, B.F. & King W. (1997) “A critical review of the Australian experience in cloud seeding”. Bull. Amer. Meteor. Soc. 78, 239-53.
- TFOT (Nd) Cloud-Seeding Yachts Sail the Seas. Retrieved 8th December, 2011. http://thefutureofthings.com/news/1274/cloud-seeding-yachts-sail-the-seas.html