In fact this suggests that dust particles are actually slow to grab
moisture. I wonder if they can be charged somehow to speed up the
process? In fact what is the relationship of charging to water
droplet formation?
What this suggests is that the process is far more sensitive than
thought.
Are some trees expressing complex organics along with transpired
water? Does this affect droplet formation?
We already know that cosmic rays have an effect plausibly by changing
charge on a water droplet and inducing it a attach to another
droplet. A charged dust particle would naturally stack up water
droplets because such a charge would not be released easily.
In any case, this item shows that the whole topic is barely explored
at all.
Exploring one of
climate's 'known unknowns'
by Staff Writers
Bristol, UK (SPX) Jul 04, 2012
One of the most
significant 'known unknowns' is how quickly water can condense on the
small aerosol particles to grow and become cloud droplets,
influencing the albedo (reflectivity) of clouds and cloud
lifetime (precipitation).
The influence of
aerosols (small particles less than 1 micrometre in diameter) and
clouds (liquid droplets 1 - 1000 micrometres diameter) represents one
of the largest uncertainties in our understanding of trends in past
global climate and predicting future climate change, as recognised by
the 2007 report of the Intergovernmental Panel on Climate Change.
One
of the most significant 'known unknowns' is how quickly water can
condense on the small aerosol particles to grow and become cloud
droplets, influencing the albedo(reflectivity) of clouds and
cloud lifetime (precipitation).
In a study published
in PNAS, Professor Jonathan Reid of the University of Bristol and
colleagues show that the rate of cloud droplet growth can be strongly
dependent on the composition of the aerosol.
For aerosol
particles that have high viscosity (equivalent to saying they behave
like treacle or even bitumen), water evaporation and condensation can
be very slow, taking many hours.
For particles that are
much less viscous (more like olive oil or even water), evaporation
and condensation can be very fast: less than 1 second.
Professor
Reid said: "Although not providing all the answers, this work
helps us better understand the 'known unknowns'. Most importantly, it
demonstrates that better understanding the rate at which water
condenses on particles in the atmosphere is crucial for
understanding clouds."
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