On Sep 10, 11:28*pm, "Bernard Burton" b.j.burton-
wrote:
Yes Will, that's OK for the dynamics. But the next step is to equate this to
the physical consequence, the thermodynamic effect, of the dynamics you
describe. The effect of the upper level convergence is to lift a substantial
layer of the upper troposphere and lower stratosphere, which of course
results in a cooling of the layer, especially well marked in the
stratosphere, where the lapse is zero or negative. It is this cooling that
more than compensates for the tropospheric warming due to subsidence and
advection, and produces the increase in pressure at the base of the
atmosphere. Mass can only increase in an atmospheric column if there is a
corresponding decrease in temperature. A map of the pressure or height field
at any level in the atmosphere is a direct reflection of the mean
temperature field (or thickness) in the atmosphere above *that level. A high
pressure 'cell' at any level will be a reflection of a cold anomaly above
that level, and a warm anomaly will be found above a low pressure area.

--
Bernard Burton
Wokingham, Berkshire, UK.

Satellite images at:www.woksat.info/wwp.html

"Will Hand" wrote in message

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"Col" wrote in message
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"Rob Brooks" wrote in message
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At long last A High of significance - had a quick look back at my
pressure readings this year and today has seen the highest pressure in
Leeds since 17 March. It's now 1038mb and still rising.

Is this really surprising, though?
In terms of pressure readings isn't a winter anticyclone likely to be
more
'intense' than a summer one?

dynamics lesson
Why? And don't say because the air is colder as that would not be the
right
answer, this high has 552DAM air entrained. The reason is all in the
dynamics - this high developed at the left entrance of a confluent
relaxing
upper trough and right exit of an Atlantic jet both regions of upper level
convergence due to ageostrophic wind components. Also we had a deep low
with
a lot of wind and kinetic energy which has been converted to potential
energy helping to raise pressure substantially. This is a warm and intense
high.
/dynamics lesson

Will
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Thank goodness someone has come up with a lucid explanation of
where the extra air is, to put it simply. i used to be a bit puzzled
about this. If you go to 30,000 feet in an anticyclone the pressure
is still higher than normal for that height so one is still forced to
ask oneself where all this "extra air" is. Above 30,000 feet,
obviously. I knew it must be in the stratosphere but it is now clear
to me how it gets there and why it causes high pressure. One could
say that the dynamical processes try to lift the lid and the lid
fights back with adiabatic cooling.
It's all a bit clearer now. Thanks, Bernard.

Tudor Hughes, Warlingham, Surrey.