Can anyone tell me how the field which I interpret to be boundary layer
cloud fraction (Grenzschichtbewolkung)
differs from the low cloud fraction he-

Boundary layer:-
http://www2.wetter3.de/GFS_00_UTC/gfs_6-12_37.gif

Low cloud:-

http://www2.wetter3.de/GFS_00_UTC/gfs_6-12_14.gif

What I'm trying to work out is what vertical 'cut-off' is used - is it
an arbitrary altitude (say 900m) or is it based upon something else? My
very limited German is not up to the job I'm afraid.

Thanks.

Martin.



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"Martin Rowley" wrote in message
...
Can anyone tell me how the field which I interpret to be boundary layer
cloud fraction (Grenzschichtbewolkung)
differs from the low cloud fraction he-

Boundary layer:-
http://www2.wetter3.de/GFS_00_UTC/gfs_6-12_37.gif

Low cloud:-

http://www2.wetter3.de/GFS_00_UTC/gfs_6-12_14.gif

What I'm trying to work out is what vertical 'cut-off' is used - is it an
arbitrary altitude (say 900m) or is it based upon something else? My very
limited German is not up to the job I'm afraid.

Martin, looking at the "expert" maps on the WeatherOnline site,
they have RH charts for 0-300m, and for 925 hPa, which seem
to be similar to the ones you quote.

Philip Eden

Martin Rowley wrote in message ...
:Can anyone tell me how the field which I interpret to be boundary layer
:cloud fraction (Grenzschichtbewolkung)
:differs from the low cloud fraction he-
:Boundary layer:-
:http://www2.wetter3.de/GFS_00_UTC/gfs_6-12_37.gif
:Low cloud:-
:http://www2.wetter3.de/GFS_00_UTC/gfs_6-12_14.gif
:What I'm trying to work out is what vertical 'cut-off' is used - is it
:an arbitrary altitude (say 900m) or is it based upon something else? My
:very limited German is not up to the job I'm afraid.

Under the charts it simply says:
"Boundary layer cloud fraction [%] Isopleths for 5, 10, 30, 60 and 95%"
"Low cloud [%] Isopleths ... "

Is there an explanation in German somewhere else that you can't read ?

Colin Youngs
Brussels

"Colin Youngs" wrote in message
...
Martin Rowley wrote in message ...
:Can anyone tell me how the field which I interpret to be boundary
layer
snip
Under the charts it simply says:
"Boundary layer cloud fraction [%] Isopleths for 5, 10, 30, 60 and
95%"
"Low cloud [%] Isopleths ... "

Is there an explanation in German somewhere else that you can't read ?

.... there doesn't *appear* to be a reference on the wetter3 (
http://www2.wetter3.de/ ) site to this particular field, and I've looked
at the NCEP/EMC site ( http://www.emc.ncep.noaa.gov/ ) and the product,
as far as I can tell, isn't discussed.
I was hoping that someone might have worked with this output and could
point me to something that would give a clue to the answer. As Philip
writes, the boundary-layer output is certainly tuned to quite a
low-level (sub 900m at least and somewhere around 300m is sensible), but
I would like to know *how* they discriminate the low-cloud and boundary
layer output for our purposes, especially over high ground/mountain
areas. Also, is it an integration over a defined altitude band (e.g. for
the boundary layer, would that be an integration from model surface to
model 600m centred on 300m, or is it explicitly centred *on* 300m? For
the low cloud, is it integrated across a layer from, say 300 m to 800 m,
or simply using a single model level *at* 925 hPa etc., etc?

Martin.



Martin.