Re: [ferret_users] grid problem y axis (latitude)

[Hella Riede <hella.riede@xxxxxxx>]

Hi Ansley,

> Hi helle,I'm working off-line and can't see your image, but I know the 
> issue. What are the units of the latitude axis?

Units of latitude axis from ncdump (original file):
float lat(lat) ;
        lat:long_name = "latitude" ;
        lat:units = "degrees_north" ;

> What is the range of 
> the y coordinate values?

From "show grid" (original file):
LAT       LATITUDE            64 i   87.863S              87.863N

As mentioned in my first email, this is already strange as the values 
inside start start +87.863 (which should be north) and end at -87.863 
(which should be south). Here are the start and end values of an "ncdump 
-v lat":

lat = 87.8638, 85.09653, 82.31291, 79.5256, 76.7369,...
    -76.7369, -79.5256, -82.31291, -85.09653, -87.8638 ;

> Is this a netCDF file?  If so then looking at 
> the y-axis information from a ncdump -c. would tell us if there's more 
> that ferret could do to issue a note or something.

Yes, it is a netCDF file and the header information and values of "lat" 
are already provided above. Is there anything else you need from the 
"ncdump -c"?

Kind regards,
Hella


> To use the dataset with reversed coordinates, the USE/ORDER qualifier 
> let's you tell ferret to reverse the Y axis.
> Ansley
>
> -----Original message-----
> From: Hella Riede <hella.riede@xxxxxxx>
> To: ferret <oar.pmel.ferret_users@xxxxxxxx>
> Sent: Thu, Oct 21, 2010 14:47:37 GMT+00:00
> Subject: [ferret_users] grid problem y axis (latitude)
>
> Dear ferreters,
>
> in our default model output, the y axis (latitude) is 
> unconventionallydefined from north to south. Working with the unchanged 
> file in ferretseems to work fine. But since ferret does not recognize 
> thisunconventional axis/grid correctly, it produces a mirror image of 
> thedata with respect to latitude when for example appending a variable 
> tothe file. This "mirroring" happens without error notice or 
> warning,which can of course lead to misunderstandings interpreting the 
> data.
>
> I prepared an example, see attachment.
>
> Thank you in advance for taking notice.
>
> Best wishes,
> Hella

--

---------------------------------------------------------------
 Hella Riede  (Dipl.Chem.)
 Max Planck Institute for Chemistry
 Dept. of Atmospheric Chemistry
 Becherweg 27                   email: hella.riede@xxxxxxx
 55128 Mainz                    phone: +49-6131-305437
 Germany                        fax:   +49-6131-305436

 homepage: www.mpch-mainz.mpg.de/~riede
---------------------------------------------------------------