Author Topic: Question about nucleating particles for airborne moisture according to season  (Read 298 times)

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Offline dustinthewind

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Recently I was invited to attend a seminar for aircraft pilots concerning understanding weather conditions in the Great Lakes region according to season. The presenter was a government employed weather forecaster.

He mentioned that during winter there are more particulate matter in the air than during other seasons. These particulate matter become nuclei which permit condensation of water upon them which helps to facilitate winter weather such as fog, rain, snow and ice of varying types.

I was puzzled by why that should be so because I thought there might be more atmospheric mixing during warmer seasons such as spring and summer when solar heating would heat more dramatically and differentially the different layers of the atmosphere. I presumed these differential warmings would promote atmospheric layer intermixing and thus winds which would pick up particulates from the surface and carry them to various altitude levels.

When I asked him about my supposition he said did not know why it was the way he described. I am aware of the changing temperature curve of the atmosphere as you increase in altitude from surface to space - in that the temperature will decrease gradually to a certain altitude and then increase modestly in temperature again from a certain altitude to a greater altitude, before resuming the decrease in temperature again as you approach space.

However, I'm not sure this would influence the phenomenon he described.

So, what might be the explanation? I know that warmer air holds more moisture than cold air. I wondered if the transition from autumn to winter might generate significant atmospheric mixing also as the the different atmospheric layers cool at different rates which would generate winds which would pick up particulates from the surface and cast them into the atmosphere and in conjunction with the increasing moisture entering the cooler and colder air layers from the various geographic regions cause this increased particulate - moisture combination?
« Last Edit: December 20, 2016, 06:33:41 AM by dustinthewind »

Offline Cutty Sark Sailor

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I know that colder air holds more moisture than warmer air.
:?:  My understanding is:
Warm air will hold more water vapor than cold air.
...something like this: It takes precipitation to purge particulates:
Winter inversion results in particulates trapped in lower 'cold' air layer, with not enough energy to move into the "warmer" layer above it (warm is relative, here). The particulate matter will gradually increase in density, since it's trapped. Not enough 'moisture' in the cold layer to condense on all the particles, so when Precip does fall, more particulates are 'left behind', increasing their 'density' in that layer. over time. When inversion eases, more and more particulates precipitate, cleansing the layers, and preparing for the next seasonal cycle.

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Offline WeatherHost

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^^  Might be something to the cleansing, but I'd think more is generated in warmer, drier periods with dusty roads, agriculture and other machinery stirring up plant matter, construction, quarry work, open camp and bonfires, wild fires, etc.

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Offline dustinthewind

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ah yes, you're correct I unconsciously juxtaposed the cold and warm air's ability to hold moisture/water vapor. I meant the other reverse of what I wrote. That is partly why I was puzzled. I thought that during summer there would be more particles but less moisture while during the winter there would be more moisture but fewer particles. The interplay of the two factors was hazy to me. (no pun intended) I have corrected the error in my original post. sorry for any confusion.
« Last Edit: December 20, 2016, 06:35:25 AM by dustinthewind »

Offline dustinthewind

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To clarify generally, in temperate regions across large areas - would there be more or less moisture in the air during summer? I would think that near coastal areas or plains without mountainous obstructions to the ocean that water vapor evaporated from the ocean would pass to these regions. Desert regions and regions beyond mountains or deep within the continental interior would not receive much moisture during the summer because air masses carrying moisture from the oceans could not travel to these regions or would be depleted of water vapor after traversing such long distances or extreme heights.

Offline Scalphunter

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Inversion layers are the traps for making the particles load up an area.  To see what it really looks loke  just find an picture of the Fairbanks area during the winter  when the temperature  drops to -20/-30.  You can see the steam colnums go up and hit that inversion layer  around 500-1000 ft agl. Then it spreads out  with out  any wind to mix up the air  the particles  just  hang around till an storm comes along  that is strong enough to break up the inversion.
  Like flying down south if you get lost  just head for the grey bubble on  the horizon it be an area where there an airport.

John

 

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