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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