Problem in sst plot

Fri May 15 14:27:17 EDT 2009

Hi Jennifer,

With 0.083333 in the ctl it does shows "LON set to 0 360". Maybe it's
something I'm doing wrong but even then it won't draw lon < 0º. I'm sending
the files I'm using for testing. The grib can be downloaded from:

http://www.ftp.ncep.noaa.gov/data/nccf/com/gfs/prod/sst.20090514/rtgssthr_grb_0.083.grib2

Thanks.

2009/5/15 Jennifer Adams <jma at cola.iges.org>

> Fil, I have downloaded a data sample and done some testing. When you open
> your descriptor file with GrADS, look at the info written to the command
> window. Does it say "LON set to 0.042 359.944" or "LON set to 0 360"?
>
> The answer will depend on whether you have enough significant digits in the
> grid increment value in the XDEF and YDEF statements in your descriptor
> file. When I use "0.083333" instead of "0.083", then GrADS calculates that
> the file does indeed 'wrap' the globe and 'set lon -180 180' works as it
> should.
>
> Jennifer
>
>
> GrADS automatically issues a 'set lon 0 360' command when it opens a file
> that wraps the globe. It
>
>
> On May 15, 2009, at 1:31 PM, Fil wrote:
>
> You are right, I swapped the results. It seems that for some reason grads
> won't draw longitude < 0º with 'set lon' starting with a negative number.
> This won't be a problem (drawing first lon > 0º and then lon < 0º) except
> for the robinson projection which has to start with -180.
>
> Adding more digits unfortunately didn't work.
>
> Thank you very much for your help.
>
> 2009/5/14 Diane Stokes <Diane.Stokes at noaa.gov>
>
>> Sorry that didn't fix all cases for you.  It worked for me running grads
>> v1.9b4 and v2.0.a3 on IBM AIX.
>>
>> I'm confused by your result with:
>>  'set lon -180 180'
>> you only see -180º to 0º.  And with:
>>  'set lon 180 540'
>> you only see 0º to 180º.  Do you have those results swapped in the text
>> of your msg?
>>
>> If you don't get advice from anyone else, I could only suggest you add a
>> couple more significant digits (3's in this case) to your increment
>> values.
>>
>>   Good luck.
>>      Diane
>>
>>
>> Fil wrote:
>>
>>> Hi, Diane
>>>
>>> Thanks a lot for your help, your solution works perfectly for polar
>>> stereographic projections. But on other projections it still doesn't
>>> show anything from -180º to 0º longitude. If I try to plot just for
>>> North America, I get an "Entire Grid Undefined" message.
>>>
>>> With 'set lon -180 180' it only draws from -180º to 0º. With lon 180 540
>>> only draws from 0º to 180º. With lon -360 0 it won't draw anything. And
>>> with 0 360 it will draw the entire globe, but with the problem (for me)
>>> of getting centered in lon 180º which cuts Europe in half.
>>>
>>> Thanks.
>>>
>>> 2009/5/13 Diane Stokes <Diane.Stokes at noaa.gov
>>> <mailto:Diane.Stokes at noaa.gov>>
>>>
>>>
>>>    Hi, Filipe.
>>>
>>>    I recently ran into the same problem with a different dataset on the
>>>    same grid.
>>>
>>>    The spatial resolution the data you are viewing is 1/12 of a degree.
>>>    The increment in the xdef and ydef statements of your control file is
>>>    0.083.  (That's how the increment is stored in the grib file, so it's
>>>    not a result of anything you did wrong).
>>>
>>>    That increment value is not sufficient to wrap the data completely
>>>    around the globe.  You have 4320 points in your xdef:
>>>     4321 x 0.083 = 358.643
>>>
>>>    If you zoom in on the north pole, you'll see the data displayed does
>>> not
>>>    extend far enough north either.
>>>
>>>    If you add a few significant digits to the increment values in your
>>> xdef
>>>    and ydef statements, eg:
>>>
>>>     xdef 4320 linear 0.042000 0.083333
>>>     ydef 2160 linear -89.958000 0.083333
>>>
>>>    you'll get a more accurate mapping of the data.  The values above will
>>>    also bring the left and right edge of the grid sufficiently close that
>>>    GrADS will know that the data does wrap the globe.  You'd then be able
>>>    to display the field when setting longitude values less than 0 or
>>>    greater than 360.
>>>
>>>      Diane
>>>
>>>
>>>
>>>    Filipe wrote:
>>>
>>>        Hello all,
>>>
>>>        I'm trying to plot sst data from
>>>        ftp://polar.ncep.noaa.gov/pub/sst/ophi/ ,
>>>        but for some reason I get a white strip at longitude 0º when
>>>        using nps
>>>        projection, as you can see from this pic:
>>>
>>>        http://img8.imageshack.us/img8/2815/userlist2.png
>>>
>>>        When using any other projection, grads only draws from lon > 0º,
>>>        as you can
>>>        see from these pics:
>>>
>>>        http://img8.imageshack.us/img8/5487/userlist1.png
>>>        http://img8.imageshack.us/img8/7201/userlist3.png
>>>
>>>        I don't know what I'm doing wrong, hope someone can help me. I'm
>>>        using
>>>        latest grib2ctl.pl, wgrib v1.8.0.12x and grads 2.05a (I also
>>>        tested v1.9 and
>>>        opengrads 2.05). I used the script http://pastebin.com/f3dc65253
>>>
>>>        Best regards.
>>>
>>>
>>>
>>>
>>> --
>>> Fil - MeteoPT.com
>>>
>>
>
> --
> Jennifer M. Adams
> IGES/COLA
> 4041 Powder Mill Road, Suite 302
> Calverton, MD 20705
> jma at cola.iges.org
>
>
>
>
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