who knows if the pressure-analyse above Greenland is real. Like today,
we see a core-pressure above 1045hPa
(http://www.wetterzentrale.de/pics/nws1s.html).

Is this real, or is this a wrong extrapolation to MSL, because the
hight there (central Greenland) is 3000m? I know that the high
pressure above the ice-feelds of Greenland are most of the time of
thermical origin, but from me the verry cold air can cause a pressure
that is as high as 1050hPa. An other problem we see there is the big
pressure-gradient, even when ther are no big depressions in the
vecinity. Is this pressure-gradient s also real.

thx

There is certainly a strong gradient at the moment. The wind at
Vestmannaeyjar in the south of Iceland is currently averaging 69
mph[111kmph] with a temperature of minus 1C. This is causing a dust storm at
the moment with a RH of 34%. Quite an evening.
On a completely different subject it was nice to see some UK SCI posters at
the COL Meeting in York on Saturday including Ron Button. A very enjoyable
day.
Ian Currie-Coulsdon
www.frostedearth.com




"eric" wrote in message
om...
who knows if the pressure-analyse above Greenland is real. Like today,
we see a core-pressure above 1045hPa
(http://www.wetterzentrale.de/pics/nws1s.html).

Is this real, or is this a wrong extrapolation to MSL, because the
hight there (central Greenland) is 3000m? I know that the high
pressure above the ice-feelds of Greenland are most of the time of
thermical origin, but from me the verry cold air can cause a pressure
that is as high as 1050hPa. An other problem we see there is the big
pressure-gradient, even when ther are no big depressions in the
vecinity. Is this pressure-gradient s also real.

thx

I must get along to one of these meetings one year, it must be great
to talk to people all with the same interest.

Keith (Southend)

***********************
Weather Home & Abroad
http://www.southendweather.net

On Mon, 18 Oct 2004 19:32:58 GMT, "Ian Currie"
wrote:

There is certainly a strong gradient at the moment. The wind at
Vestmannaeyjar in the south of Iceland is currently averaging 69
mph[111kmph] with a temperature of minus 1C. This is causing a dust storm at
the moment with a RH of 34%. Quite an evening.
On a completely different subject it was nice to see some UK SCI posters at
the COL Meeting in York on Saturday including Ron Button. A very enjoyable
day.
Ian Currie-Coulsdon
www.frostedearth.com

eric wrote:
An other problem we see there is the big
pressure-gradient, even when ther are no big depressions in the
vecinity. Is this pressure-gradient s also real.

BIKF reports 40 knots windgusts, and by looking the geostrophic wind
scale, that is consistent with the isobars gradient.


--
Paneuropean - Merate (LC)
Tasmanian forest green.

"eric" wrote in message
om...
who knows if the pressure-analyse above Greenland is real. Like today,
we see a core-pressure above 1045hPa
(http://www.wetterzentrale.de/pics/nws1s.html).

Is this real, or is this a wrong extrapolation to MSL, because the
hight there (central Greenland) is 3000m? I know that the high
pressure above the ice-feelds of Greenland are most of the time of
thermical origin, but from me the verry cold air can cause a pressure
that is as high as 1050hPa. An other problem we see there is the big
pressure-gradient, even when ther are no big depressions in the
vecinity. Is this pressure-gradient s also real.

thx

I think you are right. IMHO the extrapolation depends upon which lapse
rate is used. There is a choice of three; the saturated adiabatic lapse rate,
(SALR) the United States Standard lapse rate (USSLR) see;
http://mtp.jpl.nasa.gov/notes/altitu...Atmos1976.html
and the dry adiabatic lapse rate (DALR). I suspect that the adjustments
made to the pressure measured on the surface of the Greenland ice sheet,
to give the value quoted (1050hPa), were based on a calculation using
the USSLR. The air was descending, therefore the DALR should have been
used but, I suspect that since US rules the world, their lapse rate was used!

HTH,

Cheers, Alastair.

This link is quite instructive ... and makes the point that there is no
*perfect* way to do this - especially for regions such as Greenland.
High pressure there is ... but don't necessarily expect the gradient
wind equation to work perfectly ;-)

http://www.crh.noaa.gov/unr/edusafe/mslp/

Martin.


"Alastair McDonald" k
wrote in message ...

"eric" wrote in message
om...
who knows if the pressure-analyse above Greenland is real. Like
today,
we see a core-pressure above 1045hPa
(http://www.wetterzentrale.de/pics/nws1s.html).

Is this real, or is this a wrong extrapolation to MSL, because the
hight there (central Greenland) is 3000m? I know that the high
pressure above the ice-feelds of Greenland are most of the time of
thermical origin, but from me the verry cold air can cause a pressure
that is as high as 1050hPa. An other problem we see there is the big
pressure-gradient, even when ther are no big depressions in the
vecinity. Is this pressure-gradient s also real.

thx

I think you are right. IMHO the extrapolation depends upon which
lapse
rate is used. There is a choice of three; the saturated adiabatic
lapse rate,
(SALR) the United States Standard lapse rate (USSLR) see;
http://mtp.jpl.nasa.gov/notes/altitu...Atmos1976.html
and the dry adiabatic lapse rate (DALR). I suspect that the
adjustments
made to the pressure measured on the surface of the Greenland ice
sheet,
to give the value quoted (1050hPa), were based on a calculation using
the USSLR. The air was descending, therefore the DALR should have
been
used but, I suspect that since US rules the world, their lapse rate
was used!

HTH,

Cheers, Alastair.

"Martin Rowley" wrote in message
...
This link is quite instructive ... and makes the point that there is no
*perfect* way to do this - especially for regions such as Greenland.
High pressure there is ... but don't necessarily expect the gradient
wind equation to work perfectly ;-)

http://www.crh.noaa.gov/unr/edusafe/mslp/

Martin.

Yes, it is interesting and partly confirms what I wrote. It says:

3) The mean temperature from the surface to sea level is calculated using the
12 hour averaged surface temperature, and an assumed lapse rate of 6.5 K /
1000m. The pressure is then 'reduced' to mean sea level using this value in
the equation above. In practice, this step is performed through the use of an
"R" value, which is essentially the pressure reduction ratio based upon the
station pressure and average temperature for a given station.

The 6.5 K km^-1 lapse rate quoted there is taken from that quoted for the
troposphere in the US Standard Atmosphere. See;
http://www.pdas.com/coesa.htm

Of course it is not as simple as I am making out, and adjustments are made as
described in paragraph 4) on the web page referenced by you, Martin.

However, the 6.5 K km^-1 lapse rate is used in some climate models as the
lapse rate for the whole tropopause. I suspect that in the real tropopause
there is no layer of air where the lapse rate is 6.5 K km^-1! It is the
misuse of that lapse rate which has led to the expectation that the lower
troposphere should be warming in line with the surface.

Cheers, Alastair.