Cloud Seeding

[Blackee]

I notice that there has been a number of article recently about cloud seeding in NSW.

Is this a worthwhile exercise, or is there some bad side-affects of the practice?

[daviescr]

an interesting subject! personally I think it's a waste of time - how can anyone prove that 'seeding a cloud' makes a jot of difference - there is no way of predicting how much precipitation a cloud will drop - so who's to know if seeding clouds gives a net increase in rain? Seems to me to be very hard to quantify!

Here's a good bit of information - http://en.wikipedia.org/wiki/Cloud_seeding

[Jake Smethurst]

I also think this is a waste of time and money, particularly money. Agree totally with Chris.

Besides, why not let the weather do it's own thing ?

[Ken]

Cloud seeding has generally met with little success over the years but there does seem to have been some limited success during a few trials in recent years. It seems to be a bit more effective around the southern parts of southeast Australia, perhaps because of the very clean air coming off the Southern Ocean in winter causing the supercooled cloud droplets to stay liquid far below the freezing point. But with cold cloud seeding, there's two big problems:
1) The clouds have to be just right. They need to be deep enough so a big proportion of them is supercooled. They also have to contain enough moisture to drop worthwhile rain. But at the same time, they can't already be all frozen where you dump the silver iodide or dry ice. During drought conditions when rain is needed the most, these clouds are pretty hard to come by in the first place i.e. you can't make little fair weather cumulus clouds drop rain.
2) To get even a reasonable idea of seeding effectiveness, you have to run many many trials under strict conditions, take into account other factors that can affect precipitation and use rigorous statistical techniques to "sort the chaff from the wheat".

There's been some good footage on a few TV docos showing a well known experiment where you breathe into a very cold chamber creating a small supercooled cloud then drop dry ice shavings into it - the whole cloud rapidly turns into tiny snowflakes which drop out of the air. You can also see related examples of this when aircraft fly through a thin supercooled layer of altocumulus. It's sometimes enough to trigger instant freezing and you end up with what looks like big holes punched out of the cloud layer with blue sky inside and ice crystal virga in the middle (e.g. http://img138.imageshack.us/img138/8160/eikrrmtk.jpg
Here's one of the many video clips out there for the instant freezing of supercooled water: http://www.youtube.com/watch?v=Xe8vJrIvDQM
http://www.youtube.com/watch?v=czmQ2_ymaOo (I quite like this one as well)

And below are a couple of the more well known photos of the effects of seeding. In these cases, dry ice was dropped into a layer of supercooled stratus, triggered instant freezing and the moisture precipitated out of the cloud below the aircraft:

[crikey]

In the aftermath of severe weather events we have witnessed.. a continual debate re: climate change.
The facts are . If you pump particles into the troposphere from volcanic eruptions to man made pollutants , the air is seeded with a higher density of nuclei from which precipitation can develop. Industrial revolution
The year 1760 is generally accepted as the “eve” of the Industrial Revolution. In reality, this eve began more than two centuries before this date. ...
http://www.yale.edu/ynhti/curriculum/un ... .06.x.html" onclick="window.open(this.href);return false;
to 2011
I believe pollution emissions are greatly contributing to general global cloud seeding resulting in increased precipitation both intense rain and snow/hail.
What are your views on this?

[Ken]

The cloud-seeding flights here in SE QLD in the last few years were well publicised in the news here even before they started. There were initial problems with the project getting underway on time because of certification issues involving the installation of the silver iodide burners and modifications to the aircraft involved. I've seen some spectacular inflight footage of the flights as the aircraft fly between and through big towering cumulus clouds.

[crikey]

Ken.
Thank goodness someone is researching and keeping track.
You have got me interested.! I will take a peak on the www and see if l can find points of interest in the future. Thanks for your informative post.