Cloud Seeding

[silverback]

I read with interest some of the comments in the former post. We are starting very dry here again this year and it doesn't look good. I have become very concerned over the past few years that the cloud seeding that is done west of the #2 Highway is creating a dry pocket east of the highway. It seems that we never get the good thundershowers we used to depend on as they fade out and then re-establish further out east. Any thoughts on this or am I just mad that some insurance companies can decide whether or not I want moisture? I know of no scientific proof that this does not impact the moisture I might want.

[cowman]

This is a very interesting topic, hopefully other folks can add to the discussion.

[cakadu]

Just for fun, I typed cloud seeding into the search engine and here is what I found from "Ask Yahoo":

Cloud seeding is a form of weather modification . It can be used to disperse fog, suppress hail, or control winds, but is most often used to increase precipitation. In order to understand the process, however, a basic understanding of clouds and how precipitation is formed is needed.

As warm air rises from the Earth, it begins to cool and forms tiny droplets of water that condense into cloud droplets. Cloud droplets are formed around particles of dust, salt, or soil (called cloud condensation nuclei) that are always present in the atmosphere. These cloud droplets group together into clouds, which can form precipitation in one of two ways. In warm temperatures, the droplets in the clouds merge with many other droplets and become heavy enough to fall to the Earth as rain. (It takes millions of cloud droplets to form a single raindrop.) In colder temperatures, the droplets of water form ice crystals. Other droplets freeze onto these ice crystals, which grow larger and heavier until they fall to the ground as rain, snow, or hail.

Cloud seeding is actually a very complex process. In the simplest terms, it introduces other particles into a cloud to serve as cloud condensation nuclei and aid in the formation of precipitation. There are three types of cloud seeding: static mode, dynamic mode, and hygroscopic seeding.

Static mode cloud seeding seeks to increase rainfall by adding ice crystals (usually in the form of silver iodide or dry ice) to cold clouds. Dynamic mode cloud seeding increases rainfall by enhancing "vertical air currents in clouds and thereby vertically process more water through the clouds." Basically, in this method of seeding, a much larger number of ice crystals are added to the cloud than in the static mode. In hygroscopic seeding , salt crystals are released into a cloud. These particles grow until they are large enough to cause precipitation to form. Clouds can be seeded from above with the help of airplanes that drop pyrotechnics, or from the ground by using artillery or ground-to-air rockets

The science of weather seeding is not without controversy . Many question the validity of the results, since they are difficult to prove. Others feel that science shouldn't interfere with nature. Still others claim that increasing rain in one area decreases it in another, in effect, "stealing" rain from other lands that may be in need. Many states have also passed legislation that attempts to regulate cloud seeding and other forms of weather modification.


This is an interesting topic and I hope some readers out there can share their insights on this (controversial) topic.

[cakadu]

This definition comes from the Environment Canada (Meteorological Service of Canada) glossary:

A weather modification technique in which clouds are treated with an active substance or agent and commonly undertaken with the following goals in mind:

1. to stimulate precipitation processes;
2. to dissipate clouds or fog;
3. to suppress hail.


The only time I have witnessed it being used out here is for the third option and that is to suppress hail. I've yet to see them use it to try and bring rain here. Oftentimes we see it do as you speak of silverback and that is to take moisture away from here, drop it somewhere on the other side of highway #2 (at least that is what the assumption is) thereby leaving us dry. It takes water to make water so if they send it all away, how does the hydrological cycle complete itself?

It would be really interesting to see if they collect data that proves that the cloud seeding actually does what they intend that it does. It would seem to me that mother nature dictates what she wants and we can only alter that so much.

[cakadu]

Oops, that should read "that is the way we see it done...." Getting too late at night.

[silverback]

From what I understand, the hail suppression that is being done is handled by a private company that has made bold claims as to how effective they can be in stopping these hail events. However, they are unable to provide anything to prove that they are not drying these clouds up for a short while at the same time. They point to radar images, but in my observations a radar image does not always indicate that rain is falling from the sky.

I really would like to know why our provincial government would allow this to go on without a few more questions about the results?. Do a few acres of dry farmland get less protection than a few new houses in Calgary??

It would be great if there would be an equal effort to seed clouds for rain production as there is for hail suppression

[grassfarmer]

Could anyone give me an indication of the real prevalence of this practice? It seems to me it will be a very expensive process and I can't image it is used very often. Afterall how often does a severe thunderstorm threaten Calgary? presumably not often enough that it will noticably affect annual precipitation in affected outlying places even if it was used every time a severe storm was brewing. I assume the storms don't always come from the same direction either which should further dilute the effect of reducing precipitation in the "flight path".

[grassfarmer]

I can remember hearing about the practice being carried out in the Lacombe area years ago, but I wasn't aware it was still being done. I find this a valuable thread.

[silverback]

The private company that is cloud seeding in the Calgary - Olds area is based out of Didsbury's airport. From what I know and have seen, they pretty much hit every big cloud that forms to the west of Olds/Didsbury/ Airdrie. This is where our summer storms come from - fact. If we have any hope of a late night shower, it rolls in from the Olds area or sometimes southwest of Calgary.

In my memory, not every thunderstorm packs hailstones, so the question is why do they hit all the storms the same way??

[cakadu]

Every single time there is a bank of thunderstorms that comes in from the West Country i.e. Rocky/Caroline etc., the plane is out there seeding. I can think of no other reason for a plane to be out when there are ugly black clouds in the sky.

I should think that whomever is in charge would want to see definitive proof that this is actually working and not becoming a huge detriment to the water cycle.

I can't recall a single incident during the severe drought years when the plane was out there seeding for rain. In fact, when there looked like there might be just a faint glimmer of hope in some of the clouds, out went the plane and took whatever chance there was - away.

[grassfarmer]

So I'm still not understanding this - if you say that the thunderstorms affecting Calgary come from either the North west or the southwest of the city and the clouds are being seeded to prevent hail falling in the city shouldn't that mean the precipitation resulting from the seeding drops SW or NW of Calgary?.
Is that what you are saying happens silverback? whereas Cakadu is saying it is dry west of #2 but getting dumped on east of #2 because of storm seeding.
How can it be falling east of hiway 2 unless the storm is coming in from the east or the seeding works by preventing moisture from falling rather than triggering it? From Cakadu's post at the start I assume it is used to trigger the hail before it crosses the city - if you just seeded into the storm with the intention of it not falling until it got east of Calgay wouldn't that increase the risk to Calgary?

[grassfarmer]

would this be an undertaking of Environment Canada ? It would be intersting to learn what the rationale is for it.

[grassfarmer]

On researching this further on the internet there seem to be widely conflicting views on the subject. It's an interesting one though.
"http://www.newscientist.com/channel/earth/mg18624952.000" is an interesting read about the process in China and South Africa.

[silverback]

The result of seeding thunderclouds as I understand it is to start the release of the moisture sooner and to disrupt the formation of the extremely high "tops" on the thunderclouds that allow for hailstones to travel very high and build bigger and bigger. They are trying to produce smaller softer hailstones that will not damage cars and shingles. We did see some big hail storms last year east of Calgary, so I guess they can't stop them all, but on average over the last few years the storms that you can see brewing in the west country kinda fizzle out for 10 to 20 miles before the heat and moisture builds up again and away they go.

My main point is this - If I know I am at a risk of getting hail, I can buy hail insurance and manage my risk.

I cannot buy rain.

Without the normal rainfall that we should get, I am at a disadvantage to all the areas that are not experiencing this effect.

Perhaps a few less farmers is a good trade off for some?