Would Cloud Seeding Help our Drought Here in the Southwest?
POSTED: Tuesday, April 8, 2014 - 12:46pm
UPDATED: Wednesday, April 9, 2014 - 1:25pm
Cloud seeding in theory should help, but you still have to have some moisture
Tuesday, April 8th, 2014 — We really need some rain here in our drought stricken desert. I do hope the predicted El Nino pattern is strong enough to finally bring the Borderland some good monsoon season rainfall and heavier than normal snow fall this winter. This got me thinking about cloud seeding. I remember studying about seeding the clouds with condensation nuclei like silver iodide. I have watched a couple documentaries on the subject as well. In today’s “Weather Talk” I will explain the basics of cloud seeding, how it is used and does it really work and whether or not it could potentially help out our Borderland drought.
Let us start off with a basic definition of Cloud seeding;
Cloud seeding: The introduction of artificial substances (usually silver iodide or dry ice) into a cloud for the purpose of either modifying its development or increasing its precipitation.
Clouds are not perfectly efficient at producing precipitation. Rainfall occurs when super cooled droplets of water, those that are still liquid but are at a temperature below the usual freezing point of 32º zero (0º) they form ice crystals. Now too heavy to remain suspend in the air, these then fall, often melting on their way down to form rain. Even in dry areas the air usually contains some water. This can be made to come together and form ice crystals by seeding the atmosphere with chemicals such as silver iodide or dry ice.
The ‘seeds’ can be delivered by plane or simply by spraying from the ground.
Silver iodide or dry ice is even used to cloud seed. Silver iodide is the most common seed used. Many people discovered early on the structure of silver iodide is very similar to that of ice. The lattice structure at the molecular level is very, very close. We think that's why ice wants to bond to it.
Static cloud seeding involves spreading a chemical like silver iodide into clouds. The silver iodide provides a crystal around which moisture can condense. The moisture is already present in the clouds, but silver iodide essentially makes rain clouds more effective at dispensing their water.
Hygroscopic cloud seeding disperses salts through flares or explosives in the lower portions of clouds. The salts grow in size as water joins with them. In his report on cloud seeding,
Cloud seeding is mainly used to increase rain or snowfall, but it is also use to potentially reduce the size of hail and even to disperse fog.
Does cloud seeding work?
It is difficult to tell. Weather and climate have so many variables. If there are areas of increased precipitation, we do not know whether it would still have rained or snowed even if the clouds hadn't’t been seeded.
Success has been claimed here in the U.S.. Spain, France and Australia. In the In the United Arab Emirates, the technique is credited with the creation of 52 storms in the Abu Dhabi desert.
China has done regular cloud seeding for many years. China says the successfully used the technology in reverse to keep the Beijing Olympic Games of 2008 dry.
Howstuffworks.com quoted the Asia Times; "In Northern China, where Beijing is located, the area does not receive much rain, its rainfall levels are 35 percent below the world average, and some of its water supplies are significantly polluted. The area relies heavily on cloud seeding. Zhiang Qiang, who runs the Beijing Weather Modification Office, told the Asia Times that water levels in Beijing's water basins have increased up to 13 percent due to cloud seeding. Cloud seeding also has been used to cool Beijing on hot days."
According to weathermodification.org; “Yes, it can be very successful. But like any tool it has its limitations, and sometimes cloud seeding can be ineffective. Studies have shown certain clouds or stages of cloud development are susceptible to seeding while others are not. Cloud seeding will not “end” a drought, although it may provide some increases in precipitation even during drought periods. The seeding agents and methodologies used in present day cloud seeding projects have been developed and refined for over 60 years. There is some consensus that cold cloud seeding technologies can increase area-wide seasonal precipitation by approximately 5-15% when the seeding is effectively applied to suitable clouds.”
The best time to do cloud seeding is when you have normal levels, or higher-than-normal levels, of precipitation.
Many scientists and organizations keep trying to discredit cloud seeding. Cloud seeding remains popular because of the demand for water, especially because of areas of the world that are in a drought, like here in the dry, desert southwest. Cloud seeding is considered a relatively inexpensive way to possibly acquire more water.
Cloud seeding will continue and will probably even grow into a much bigger industry as the world has ever increasing demands for water. The seeds added to a cloud do increase the chances of condensation on the seeds themselves, is it enough to cause more rain than normal to fall out of that cloud? If the science does become more advanced it would be fantastic to have a cloud seeded that is traveling right over my yard!