Interesting read.
http://www.sciencedaily.com/releases/2008/12/081208114258.htm

Interesting, but is there anything new there? Soaring books published
twenty years ago have drawings depicting the sinking air around
thermals as well as the idea that thermals are streams of bubbles vs
columns. Maybe its just that now they are taking this into account in
the models?

Mike

On Dec 19, 8:10*am, wrote:
> Interesting, but is there anything new there? Soaring books published
> twenty years ago have drawings depicting the sinking air around
> thermals as well as the idea that thermals are streams of bubbles vs
> columns. Maybe its just that now they are taking this into account in
> the models?
>
> Mike

Yes, there's a lot here because now they have a mathematical model for
it.
We've always known it as lore, intuition, etc., but for weather and
climate
models fair weather clouds are just fudge factors. Now (at least on
the
fine scale) they can accurately model them.

On Dec 19, 11:50*am, wrote:
> On Dec 19, 8:10*am, wrote:
>
> > Interesting, but is there anything new there? Soaring books published
> > ........................

What I got from the article is that the new model predicts sinking air
around the edge of the CLOUD. But most of our soaring is done below
the cloud so concentrated sinking air is not predicted in those
surroundings because the evaporation mechanism is not present there.

snip-
Heus continues, All around the cloud, air sinks downward in compensation for the upward movement.
-snip

What bunk

Hues should perhaps remind himself of gravity, and that his models dont seem to take it into account


bagger

On Fri, 19 Dec 2008 16:49:07 -0800, Rudy Allemann 7Y wrote:

> On Dec 19, 11:50Â*am, wrote:
>> On Dec 19, 8:10Â*am, wrote:
>>
>> > Interesting, but is there anything new there? Soaring books published
>> > ........................
>
> What I got from the article is that the new model predicts sinking air
> around the edge of the CLOUD. But most of our soaring is done below the
> cloud so concentrated sinking air is not predicted in those surroundings
> because the evaporation mechanism is not present there.
>

Reading between the lines I'm guessing that up to now climate models have
taken account of the effect of clouds on the earth's albedo and
(possibly) reducing heat loss by trapping long wavelength IR radiation
beneath them, but ignored or fudged thermal mixing effects under cu. Now
they know enough about the mixing effect to incorporate it in their
models.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |

On Dec 19, 4:49 pm, Rudy Allemann 7Y > wrote:
> On Dec 19, 11:50 am, wrote:
>
> > On Dec 19, 8:10 am, wrote:
>
> > > Interesting, but is there anything new there? Soaring books published
> > > ........................
>
> What I got from the article is that the new model predicts sinking air
> around the edge of the CLOUD. But most of our soaring is done below
> the cloud so concentrated sinking air is not predicted in those
> surroundings because the evaporation mechanism is not present there.

Actually, I've encountered sharp edged sink as I passed the cloud edge
when leaving a good Cu. Sometimes, this caused negative G. I suspect
the evaporation caused cool air downdraft extends well below cloud
base. I plan to pay closer attention in the future.

All the models do incorporate gravity (otherwise less dense air would stay
exactly where it is, and no convection).

They are of course 'models' - a mathemetical description of behaviour if
a variety of assumptions are correct. When I was involved in Met. research
in the 1970's it was clear that the models used then for meso scale (the
scale on which usable convection occurs) gave very poor correlation with
reality. My understanding is that the models today are more refined, but
still are nowhere near matching the complex reality where topographic
effects and a mixture of airmass trajectories have large effects on the
behaviour. Trying to explain observed effects assuming a homogenous
airmass over a uniform surface (or even one varying regularly) are
interesting to mathematicians but almost totally irrelevant to soaring
pilots.

At 01:13 20 December 2008, bagmaker wrote:
>
>snip-
>Heus continues, All around the cloud, air sinks downward in
>compensation for the upward movement.
>-snip
>
>What bunk
>
>Hues should perhaps remind himself of gravity, and that his models dont
>seem to take it into account
>
>
>bagger
>
>
>
>
>--
>bagmaker
>

bagmaker wrote:

> Hues should perhaps remind himself of gravity, and that his models dont
> seem to take it into account

Bagger sould perhaps remind himself that there is probably more in the
whole study than is reflected in a magazine's headline.

Peter Purdie wrote:
My understanding is that the models today are more refined, but
> still are nowhere near matching the complex reality where topographic
> effects and a mixture of airmass trajectories have large effects on the
> behaviour. Trying to explain observed effects assuming a homogenous
> airmass over a uniform surface (or even one varying regularly) are
> interesting to mathematicians but almost totally irrelevant to soaring
> pilots.

And yet, the Blipmap cumulus forecasts for cloud location, cloudbase,
and cumulus potential are relevant and useful to soaring pilots. Don't
these values come from the models?

--
Eric Greenwell - Washington State, USA
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