Height from Geopotential not working any more

[hproe]

Running recent build of 1.02beta1 I realise that the derived quantity "Height from Geopotential" does not work (any more). Recent builds of IDV work correctly. The error messages issued are:

Creating display: Contour Plan View
TypeError: unsupported operand type(s) for /: 'visad.FieldImpl'
and 'visad.Real'
org.python.core.PyException

Traceback (most recent call last):
File "<string>", line 1, in <module>
File "<string>", line 372, in GP2Z
TypeError: unsupported operand type(s) for /: 'visad.FieldImpl' and 'visad.Real'

I have attached ECMWF.grib as a sample.

HP

[barryr]

Hi HP,

Thanks for the report. I've filed it as McV inquiry 1129:
http://mcidas.ssec.wisc.edu/inquiry-v/?inquiry=1129

Barry

[Rick]

Hi HP,

Looks like the file ECMWF.grib is no longer on the forum. When you get a chance, please re-post.

Thanks,

Rick

[hproe]

Hi Rick -

Most probably the sample file output.grib did not upload at the time I wrote the bug report. I realise now that I am told the extension grib is not allowed. I also tried grb - no way. The upload worked with the extension txt. So, look for output.txt. In case it did not upload correctly this way, tell me where I can stage the file with simple ftp.

HP

[mug_admin]

Hi HP,

I was able to get your data to contour (including 3D) in both McV and found the same results in the IDV.

For McV

From Data sources:
Gridded Data -> Local

From Field Selector
3D Grid -> Derived -> Geopotential @ isobaric

From Displays
3D Surface -> Contoured Parameter as Topograpy

The units were a little unexpected (m**2/s**2). Let me know if this is what you were trying, otherwise it seems as though this might have been fixed in one of the nightly releases. Note, I have tried both XP and Linux 64.

[hproe]

Hi -

I realise now that my reaction to the answer from mug_admin did not make it to the forum.

Okay, the plot shown in the last post is a plot of geopotential and *not* of geopotential height. That is why you get the unit shown - it is the correct unit for the geopoential. The ECMWF archive (unlike NCEP?) only delivers the geopotentialas a primary parameter (see my example (ECMWF.grib) on your ftp server. For the geopotential height you have to go to the derived quantities (Height from Geopotential...) and the reported error occurs.

HP

[Rick]

Hi HP,

Thanks for the clarification. I wrote up an inquiry.

http://mcidas.ssec.wisc.edu/inquiry-v/?inquiry=1184

Rick

[hproe]

Hi -

News from plotting geopotential height with grid files from the ECMWF archive.

ECMWF only delivers geopotential (parameter name: Geopotential_isobaric) and no geopotential height, i.e. the geopotential height has to be obtained as a derived quantity. However, with standard McIADS-V builds it is missing due to a missing alias. The height is calculated with the formula GP2Z(D1), to be found under 'Derived Quantities' and as a method in the Jython library > System > Grid Routines. The argument D1 is passed with parameter name 'GP', i.e. with the Alias Editor a new entry under the 'User aliases' tab has to be created that aliases 'GP' to 'Geopotential_isobaric'. This alias results in 2 additional derived quantities to appear: Geostrophic Wind and Geostrophic Wind Vectors.

HP

[bobc]

Hi HP -

Thanks for the update. Good catch! Adding a User Alias for GP>Geopotential_isobaric allows 3 more derived fields to list: 'Height from Geopotential', 'Geostrophic Wind Vectors', and 'Geostrophic Wind'. I updated inquiry 1129 with this information, and proposed changing the System Alias from:

Name: GP
Description: Geopotential
Aliases: Geopotential

to...

Name: GP
Description: Geopotential
Aliases: Geopotential,Geopotential_isobaric

This would allow for cases where data that uses 'Geopotential' as well as 'Geopotential_isobaric' to be properly recognized as geopotential parameters.

Thanks again!
Bob