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[IDV #WWB-790357]: simple difference on objective analyses

Hi Brian-

> I've uploaded a zipped IDV bundle called simpledifference.zidv. The
> comparison is between two precipitation fields. In this file, the fields
> are unitless, but I have tried specifying mm in the text file header and
> using newUnit on the vis5d file and get the same result.

Thanks for the files.  You definitely need to do the newUnit on the Vis5D data. 
I can get it to work if I subtract the v5d from the gridded point obs, but not 
the other way around.  I'll look into that further when I get into the office.

> -----Original Message-----
> From: Unidata IDV Support [mailto:address@hidden
> Sent: Wednesday, December 02, 2009 3:52 AM
> To: Billings, Dr. Brian, Contractor, Code 7533
> Cc: address@hidden
> Subject: [IDV #WWB-790357]: simple difference on objective analyses
> Hi Brian-
> > Full Name: Brian Billings
> > Email Address: address@hidden
> > Organization: Naval Research Laboratory Package Version: 2.7u2
> > Operating System: Windows Vista
> > Hardware:
> > Description of problem: Have any issues been reported on using the
> simple difference formula where one of the fields is an objective
> analysis of point data? I have been trying to use this option on a 2D
> vis5d file and a text data listing. The times are the same and the units
> are the same, but the results are obviously incorrect. The users guide
> says that the calculation is automatically performed only on the area in
> which the grids overlap, but this is not being done in my output. Is the
> issue with using an objective analysis or some other possibility?
> Thanks.
> If you are subtracting temperatures, the values will end up in K so if
> you convert to Celsius you'll be off by a factor of 273.  The IDV does
> not distinguish between delta degrees K and regular K so a conversion
> between units will treat them as absolute.
> If that's not what you are seeing, could you upload the vis5d file and
> the text data to:
> http://motherlode.ucar.edu/repository/alias/idvupload
> so I can take a look.  Let me know what field you are trying this with.
> Don Murray
> >
> >
> Ticket Details
> ===================
> Ticket ID: WWB-790357
> Department: Support IDV
> Priority: Normal
> Status: Open

Ticket Details
Ticket ID: WWB-790357
Department: Support IDV
Priority: Normal
Status: Open

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