Help on EASE-Grid Weekly Snow Cover data

[Jennifer Adams]

The EASE grid is not a polar stereographic projection, so PDEF NPS
won't work. As I see it, you have two choices:
1. Use the PDEF bilin option, which means you have to generate your own
pdef file.
2. Convert the EASE gridded data to station data format.
Both  options require some programming outside of GrADS, you'll just
have to decide which will be easier and better for your needs in the
long run. If all you know about the EASE grid is the lat/lon of each
gridpoint, then option #2 will be simpler. Option #2 will also preserve
the equal-area nature of the native grid. If you can calculate where a
given lat,lon would be in the i,j space of the EASE grid, then option
#1 might be the better choice. Please see the PDEF documentation for
details on what you need to put in the pdef bilin file.
Jennifer



On Jul 7, 2005, at 2:22 AM, Prince K. Xavier wrote:

> Hello all,
>
> Thanks Arindam. I did it in another slightly tricky way. But now
> there's the
> problem of pre-projected data. The grid is 721 columns by 721 rows,
> with the
> North Pole positioned at the center of the center pixel. Spatial
> resolution is
> 25 km. The CTL file I wrote looks like this.
>
> dset ^test.grd
> undef 254
> pdef 721 721 nps 360 360 180.0 25
> xdef 721 linear 0 0.5
> ydef 721 linear 0 0.125
> zdef 1 linear 1 1
> tdef 1 linear 1jan1966 1dy
> vars 1
> sn 1 100 1 * snow
> endvars
>
> But it gives a distorted representation of the data. (Please see the
> attachment.) Could anyone please help me to figure out what went wrong?
>
> Regards
> Prince
>
>
>
> On Mon, 4 Jul 2005 11:32:02 -0400, Arindam Chakraborty wrote
>> dear Prince,
>>         reading the variable as integer(1) in a fortran program
>> should solve your problem. However, 1-byte unsigned characters can
>> be read in GrADS directly by writing -1,40,1 in the units field of
>> the variable in the descriptor file.
>>
>> regards,
>>
>> arindam
>> ----------------------------
>>  ARINDAM CHAKRABORTY
>>  Department of Meteorology
>>  Florida State University
>>  Tallahassee, FL-32306, USA
>>  Tel: +001-850-6443524 (Off)
>>       +001-850-5758550 (Res)
>>  Fax: +001-850-6449642
>> ____________________________
>>
>> On Mon, 4 Jul 2005, Prince K. Xavier wrote:
>>
>>> Hello,
>>>
>>> I have a slightly out of topic query. I am trying to convert the
>>> Northern
>>> Hemisphere EASE-Grid Weekly Snow Cover and Sea Ice Extent Version 2,
>>> to
>>> Grads format, which is written in Flat binary files with arrays of
>>> 721
>>> columns by 721 rows of 1-byte unsigned integers.
>>>
>>> My query is, whether it is possible to read it as 1-byte integers in
>>> fortran, than reading it as character?
>>>
>>> If anyone has faced this problem before, please let me know how you
>>> have
>>> resolved it.
>>>
>>> Thanks in advance
>>> Prince
>>> --
>>> Prince K XAVIER
>>> Centre for Atmospheric and Oceanic Sciences
>>> Indian Institute of Science
>>> Bangalore - 560 012
>>> INDIA
>>> http://caos.iisc.ernet.in/hpg/students/prince.html
>>> __________________________________________________
>>> Phone No.
>>> +91 80 2293 2505 (Extn:201)
>>> +91 98808 19172  (Mobile)
>>>
>
>
> Prince K XAVIER
> Centre for Atmospheric and Oceanic Sciences
> Indian Institute of Science
> Bangalore - 560 012
> INDIA
> http://caos.iisc.ernet.in/hpg/students/prince.html
> __________________________________________________
> Phone No.
> +91 80 2293 2505 (Extn:201)
> +91 98808 19172  (Mobile)
> <test.gif>
--
Jennifer Miletta Adams
Center for Ocean-Land-Atmosphere Studies (COLA)
4041 Powder Mill Road, Suite 302
Calverton, MD 20705 USA
jma at cola.iges.org