Could it be, Dave, that the model data you quote is incorrect? The midday
ascents show 850 mbar temperature in the range -7 (Albermarle) to -9 (De
Bilt). The closest to your model value was Paris (-10), but the surface temp
there is -3.
Another thing, if the lapse rate is equal to the dry adiabat, it indicates a
well mixed layer, not the opposite. You can not have a shallow surface layer
warmed by the underlying sea, with colder air above, and also have an
unmixed layer at the surface. When cold air overlies a warm sea, there is a
flux of heat from the sea to the atmosphere, and this will lead to a well
mixed boundary layer up to where ever the capping inversion is. In today's
instance, using the ascent for Nottingham at midday, there is a dry lapse
rate up to about 950 mbar, then a saturated lapse up to a capping inversion
at 800 mbar, T= -10. The layer surface to 800 mbar presents a well mixed
layer with convection up to 800 mbar.
The GFS vertical charts for Europe (1800z) do not show 850 mbar temps
anywhere near -11 between 49N and 69N on the Greenwich meridian.
http://www.wetter3.de/vertikal.html
Watch for the line wrap!
http://weather.uwyo.edu/cgi-bin/soun...F%3ASKEWT&YEAR
=2010&MONTH=02&FROM=1312&TO=1312&STNM=03354
--
Bernard Burton
Wokingham, Berkshire, UK.
Weather satellite images at:
www.woksat.info/wwp.html
"Dave Cornwell" wrote in message
...
Just when I thought I'd mastered some of the maths involved in the
relationship between things like 850hPa and max temp etc today seems to
have
thrown quite a big spanner in the works. At 2pm temp was 4.6C under full
cloud. There was some light rain about. According to the GFS hires the 850
hPA was -11C at that time for this location. I realise the lower
atmosphere
is a 3D model but this does seem to be a bit extreme with no solar
heating.
I have to presume that the slack NE flow is producing an unmixed layer
very
close to the surface which is then giving a temperature reflective of the
current temperature of the North Sea rather than the air aloft which would
normally be used for a max temp calculation. This would also explain the
colder temperatures further west despite the higher 850 hPa's.
Dave,
S.Essex