Big Clouds From Little Forest Particles Grow

Over a decade ago I developed this idea of ‘stories’ to tell the soon-to-be-arriving grandchild about how the world works. And I planned to add a bit of mystery to the mix … my late wife called them little lies that might foster confusion more than elucidation.

One little ‘lie’ was  the idea that mountains grow up just like other things. They are continually being born as smaller rocks in the root balls of trees. The next time you see a freshly knocked over pine tree with an exposed root ball take a peek at it and you will see all these rocks embedded in the dirt and roots … just like little eggs 😉

Another thing born in the trees is clouds … as you drive through the mountains it’s easy to get that impression. The mist seems to rise from the forest and as it climbs it appears to feed the cloud cover.

Well now that particular idea is harder to knock down. Researchers in Finland have discovered aerosol particles apparently appearing from nothing – in mid air in the pine forest. Particles that promote cloud formation. When they looked closer they discovered that this was from vapours that come from the pine trees.

Anything that floats around in the atmosphere is an aerosol.

Knowing this about pine vapours is rather important since airborne aerosols are a big unknown in climate models. (I just realized the pun in that statement – airborne … born in the air) Clouds reflect solar radiation and that’s a cooling effect. Some aerosol particles also reflect but if you don’t know they are there OR are guesstimating how much there is you model may be off. When you’re trying to model climate you need to account (as much as possible) for all the things that go into the mix to get a model that more closely corresponds to reality.

But how do you get from a vapour (gas) to a particle (solid)?


The thinking was that the vapour molecules combine with ozone molecules and the resulting agglomeration grows and grows with each addition. It starts about 1 nanometer in size and grows to a 3 nanometer particle and these further combine together to become bigger ones of nearly 100 nanometers. So far so good – that explains how you get solids from essentially gases. But the chemistry models predicted a slower growth rate than observation found! Much speedier growth: instead of 3 to 5 Oxygen molecules a day being added what they found is: it is more like 10 to 12. As much as 3 times as fast as they thought.

You can read more about it in the ScienceDaily article here:

clouds_being_bornSo do those wisps of mist I see rising to the sky come from this process? – or the night’s condensation evaporating with the day’s sunshine and heat?
I know what I’d tell my grandchild first …

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