Does more dust equal more contrails?

SR1419

Senior Member.
according to this article/research paper, the amount of airborne dust doubled in the 20th century.

The are seemingly referring to terrestrial/household dust...but I am wondering if this can be related to more "aerosols" at flight level- leaving more condensation nuclei for contrails...and thus more contrails. More contrails for any given level of air traffic...

Any thoughts?


http://www.nytimes.com/2011/02/10/garden/10dust.html?src=me&ref=general
 

Mick West

Administrator
Staff member
From the paper (which is largely about desert dust):

http://www.atmos-chem-phys.net/10/10875/2010/acp-10-10875-2010.pdf
However, we can estimate the importance of these large changes in aerosol amount on the clouds based on es- timates from the last Intergovernmental Panel on Climate Change assessment report (IPCC) (Forster et al., 2007) and assuming that aerosols act as cloud condensation nuclei in proportion to their aerosol optical depth (Rosenfeld et al., 2008). Observations suggest that aerosol optical depth is a good proxy for cloud condensation nuclei, independent of their chemistry (Rosenfeld et al., 2008), because the num- ber and size of particles is important (but not their mass). While desert dust particles are largely insoluble, they are hy- drophilic (Koretsky et al., 1997), readily attracting condens- ing water, and thus likely to be heavily involved in cloud formation

It's probably not going to increase the frequency of contrails, but might influence their size and spreading.
 

SR1419

Senior Member.
That makes sense...contrails will form only if conditions are right...more or less dust doesn't change that.
 

Jay Reynolds

Senior Member.
Probably the most experienced contrail scientist in the world once joined in debunking using the handle "Canex". You can figure out who he was, some people eventually caught on His input is the most reliable I can point anyone to regarding the subject of how, why, when and where contrails form.

You might have to pick through a lot of chaff to find his 164 posts but they are here:
google advanced search within domain chemtrailcentral.com and keyword canex
 

Mick West

Administrator
Staff member
Sad though that such a large amount of reason and science would end up scattered with that chaff. Eventually he gave up perusing that particular avenue.

I like posting on forums, but you've got to recognize that there you have a very small audience, and at best it's a tool for gathering the various talking points, and practicing refutations.

Chemtrails is a subject I prefer over, say, 9/11. It's more tangible - you can almost hope to address the entire subject with a fair degree of certainty. But you can't do it one bit at a time, here and there with random people. Canex spent a lot of time on chemtrailcentral, but I can't help but think what might have been if he'd devoted that time to a more centralized and focussed exposition of the actual fact.
 
U

Unregistered

Guest
That makes sense...contrails will form only if conditions are right...more or less dust doesn't change that.
Except that contacting dust will take the supersaturation out of a stratospheric layer of the sort that would be a good host to spreading contrails, and therefore diminish their effects.

Supersaturation and dust are mutually exclusive, aren't they?

Hi. :)

It's Jazzy here... I thought I'd logged in...
 

MikeC

Closed Account
My understanding from RossM on CS is that they are not mutually exclusive for ice saturation - ice will only form on suitable particles, and most dust is not suitable.

But another ice particle is - hence when a contrail does form it can "spread" relatively quickly.
 

Mick West

Administrator
Staff member
See:
http://www.atmos-chem-phys.org/9/3505/2009/acp-9-3505-2009.pdf

Today’s state of knowledge is that the freezing thresholds
depend on the compounds of the available ice-forming
aerosol particles. If these particles are pure liquid solutions
(of arbitrary composition), the – homogeneous – freezing
thresholds range for 140...180% for T =240...180 K and are
well described by the theory derived by Koop et al. (2000).

In the presence of aerosol particles containing an insoluble
impurity (so called ice nuclei, IN, such as soot, mineral
dust or biological particles), the – heterogeneous – freezing
thresholds are determined by the composition of the particles.
Therefore, up to now no simple parametrisation scheme
exists for the heterogeneous freezing thresholds. In most
cases they are lower than the homogeneous freezing thresholds
and can be significantly different. Thus, injection of
aerosol particles with a lower freezing threshold would directly
impact the cirrus cloud cover and thus the radiation
balance of the atmosphere (Gettelman and Kinnison, 2007).

So, yes, it depends on the type of dust.

It's surprising the amount of uncertainty in the subject of exactly how clouds form. I suppose that's mostly due to their scale and unusual location. Still, you'd think there could be a bunch of fairly obvious experiments that could be carried out in a sufficiently large low pressure refrigerated chamber.

Here's one from 2006.
http://www.nature.com/news/2006/060424/full/news060424-7.html

An office block with a huge silver silo perched on top of it seems an unlikely place to produce clouds. But nestled within just such a building at the Leibniz Institute for Tropospheric Research in Leipzig, Germany, lies some cutting-edge equipment: an 8-metre long, pencil-thin steel tube that can hold man-made clouds.

The facility, called the Leipzig Aerosol Cloud Interaction Simulator (LACIS), was launched this Tuesday after seven years of planning and construction, at a cost of nearly 3 million euros (US$3.7 million). "This is a dream that we cloud researchers have had for 20 years, to bring clouds into the lab," says institute director Jost Heintzenberg.

The simulator should allow researchers to investigate in depth the processes by which cloud droplets form on bits of particulate matter in the air, called aerosols. With a better understanding of such processes, researchers hope to elucidate how cloud cover affects climate (and vice versa), and how these effects may change in the future thanks to mankind's activities.

...

The narrowness of the channel helps the researchers to measure just one particle or droplet with the spectrometer at a time. This means researchers can study in detail how soot, salt or biomass particles spur cloud growth at different temperatures and humidity. From that, says Heintzenberg, researchers can calculate factors such as how big such clouds would grow under the same conditions outside, and how much they would reflect sunlight — a crucial part of climate studies.
 
Top