[ferret_users] missing values and scale factors interfere?

["Grant Andrea Nicole" <andrea.grant@xxxxxxxxxxx>]

Hi,
 
I have a netcdf file of the CRUTem2v global surface tempertures from the Climatic 
Research Unit (http://www.cru.uea.ac.uk/cru/data/temperature/).
In the attributes the 'scale_factor' is set to 0.01 and 
'missing_value' is set to -9999. In the file, the raw data indeed contains many
-9999. However, when I read it into ferret, these all become -99.99 after the
scale factor is applied and when I then try to do a shade command the 
colorbar scale is worthless because so many -99s are plotted. It is easy
enough to work around by defining
 
set ver/bad =-99.99 my_var
 
but I'm wondering if this is something that could be fixed? The other programs I've
used (grads or matlab) are able to interpret this combination correctly. Or is
it that the header should be defined differently, but possibly then other software
wouldn't interpret it correctly? I am new to gridded data and not sure if there is
a universal convention about these sorts of things.
 
Thanks,
 
Andrea
 
 
Andrea Grant 
Institut für Atmosphäre und Klima 
ETH Zürich 
Universitätsstrasse 16 
CH-8092 Zürich 
Schweiz 
Tel: +41 (0)44 632 79 75 
andrea.grant@env.ethz.ch