Keith (Southend) wrote:
Martin Rowley wrote:
"Keith (Southend)" wrote in message
...
I was wondering, given this current cold few days, how DAM
thicknesses were calculated.

... the total thickness (or Relative Topography for continental users)
is the given by the separation of the 500 hPa and 1000 hPa surfaces -
bigger numbers, warmer air, smaller numbers colder air. To keep an eye
on such, you need to know both the height of the 500 hPa surface and
that at 1000 hPa. The latter you could in fact compute from a
surface-based instrument, as is standard practice for radio-sondes
(using the mslp & screen temperature), but you can't ascertain the 500
hPa height from the surface - you need a radio-sonde (or satellite
sounding) for that.

To look at actuals from radio-sonde ascents, try this ...

http://weather.uwyo.edu/upperair/europe.html

leave the default ('Text List'), and then click on the station you
want to interrogate. Scroll down the list nearly to the bottom and you
will find the 1000 - 500 hPa thickness given (in metres).

Martin.

Thanks Martin,

I remember that link from before, but I never realised the thickness was
there. I guess 5344 we would think as 534 DAM ?
03882 Herstmonceux Observations at 12Z 03 Mar 2009

Best regards

Keith (Southend)


Yes, 5,344 metres is 534.4 decametres

http://en.wikipedia.org/wiki/Decametre

Your Davis weather station could roughly calculate this if you can
attach a probe a long way up a pole!

Joe