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Tagged: Hagelabwehr; silver iodide
One of the more unusual sights in Charleville (Queensland, Australia) are the conical shaped Vortex Guns that are on display for people to admire. It is well known that “desperate times call for desperate measures” … but in 1902 a renowned meteorologist by the name of Clement Wragge arrived in town to end what was then the longest running drought in Queensland’s history. His proposed solution was to use six massive vortex cannons which had been developed by an Austrian scientist named Albert Steiger to dispel hail bearing clouds in Europe. Wragge intended to await the arrival of suitable clouds then fire rain producing gas into the atmosphere above the town and fully expected the rapidly rising charges from the guns to force the clouds to release their rain. Needless to say the experiment failed, one of the guns exploded and narrowly avoided injuring a number of the town’s curious observers!
Thanks for sharing this wonderful story George. I know more attempts have been done to manipulate the weather by seeding but I don’t know about any positive result – under acceptable conditions – until now. Who might know more about this?
Hello Hans – the man to ask is no one else than the founder of the CAS himself, Gavin Pretor-Pinney! In his book he describes the top secret programme adopted by the Americans to spray chemicals into the clouds over Laos, Vietnam and Cambodia in order to create rain, extend the monsoon season and thereby disrupt enemy movements along the Ho Chi Minh trail (a major infiltration route). Given the code name Project Popeye the idea was to “make mud not war’. Tests were conducted in 1966 over the Annam Mountain Range in Laos.
Another source of information is Mark Miodownik (author of book ‘’Liquids’’, 2018). He maintains cloud seeding, regarded as “one of the most extraordinary experiments of the 20th century”, was invented in 1946 by an American scientist called Vincent Schaefer. He and his team maintained that by dispersing silver iodide crystals into the atmosphere they would act as nucleating droplets (like dust or smoke particles do) which would produce snow and rain.
Thank you George for your explanation. I now remember what Gavin wrote about it. I did some search on the subject and what I found is that attempts to use it are not successful while there also are considerable concerns about environmental damage.
Ha, this is my old domain. One on my college thesis (that was VERY long ago) was on this subject. The focus was hail prevention, but the theory is the same, The freezing nuclei are needed to get the precipitation going. For hail prevention in particular, the idea is that while there are freezing nuclei, there are too few, so a few crystals get to grow to huge sizes and come down as hail. If you provide a lot of nuclei, there will be some more even distribution.
Later on, when I was working at the Meteorological Institute in Romania, we had a program where we would watch on the radar for clouds that can potentially carry hail and would send an alert to a couple of clients (vineyards, whose crops are the most affected by hail) who would launch small rockets dispersing silver iodide.
The problem with both rain making and hail prevention is that it’s very difficult to prove it works (or not). I remember some studies where two very similar areas were selected and one or the other was seeded at random. It was inconclusive.
I found this article that seems to say the technique works. At a 5-15% increase in precipitation, I am not convinced it’s not just normal variability.
Thank you George – always good to have input from someone that has had your depth of experience.
Thank you too for the Pewtrusts link, the information from which I have found most interesting. The severe droughts farmers have been experiencing in Australia over the last decade, said to be “the longest in living memory”, have broken at last what with much of the drought affected areas now under metres of water, roads cut off and floods downstream. It is simply the timing of such events that doesn’t always meet human needs?
Can either of you confirm whether there is any connection / correlation between the heavy rains (and hail) we have just experienced and the tons of combustion particles that went up in smoke as pyrocumulus clouds during the three month long bush fire crisis Australia has just suffered? Or is this simply a co-incidence?
Hail prevention with agricultural aircrafts is well known in Germany/Bavaria as well as in Austria , France and Russia.
Light aircrafts spray silveriodide into clouds with the hope of preventing raindrops changing into hail,
This form of hail preventing had been performed for some 50 years as a standard method.
For details see German WIKIPEDIA https://de.wikipedia.org/wiki/Hagelabwehr
Thanks Martin, good article. Yes, there is some business around rain making and hail prevention. The problem is proving cloud seeding effectiveness. Here is what the article says (translated from German by Google).
Evaluation of the applicability and effectiveness
Hail cloud with a characteristic greenish color
While an effect is theoretically conceivable and justifiable, in practice there are great problems with all the methods used in the actual introduction of silver iodide into suitable cloud layers at the right time because the local weather conditions fluctuate greatly. So far, there have been no scientific studies on measuring success, and no clear results could be derived from company investigations.  For the increased, targeted raining by means of cloud vaccination, an effect of only 10% change in the amount of precipitation could only be statistically proven.  Israeli studies question whether the method is more effective. With larger storm clouds (approx. 3 km in diameter), even with careful estimates, at least 2 ⋅ 10 18 drops must be assumed, which can potentially form hail. Assuming the production of 2 ⋅ 10 13 condensation nuclei per gram of silver iodide used, even with the distribution of several hundred kilograms of the substance, it is hardly possible to assume sufficient nuclei to produce a greater effect. 
Accordingly, attempts to bring certain rain clouds to rain down the water content ( artificial rain ) using such a technique frequently failed , in order to make certain major events rainproof, such as the May 9 parades in Moscow in 2005 and 2008 or the arrival of the Olympic Feuers in Peking 2008. The successes reported are controversial.  Russian meteorologists also announced that they wanted to prevent rain at the G8 summit in St. Petersburg 2006 using silver iodide, but during the conference there were cloudbursts. 
George, I cannot confirm, that’s too strong a statement, but the fires have certainly increased the natural convection, which is the main mechanism of cloud formation, specifically for cumulonimbus. Also, there is additional water vapor generated by the fires, so you have all the ingredients to form a storm cloud.
Somewhat relevant to this topic, perhaps, the environment agency in South Wales (UK) said on TV today that a flooding river was flowing at 900 tons of water per second (sic).
P.S. Hans, did I miss an introduction to your thumbnail photo companion? Looks about the same size as a Great Dane I once knew.