Re: transform a projection into regular lat-lon

Hi Mark,
After playing around with your data file for awhile I think I figured out the correct settings for NCL to generate a native plot.
Given the rotated pole attributes you have below NCL needs the following settings:

res@mpCenterLonF = -162 + 180.
res@mpCenterLatF = 90 - 39.25

I am not familiar with this method of specifying the rotation but it seems to produce the correct results. I am attaching a png file and a script that draws the data both in the native projection and a different arbitrary projection.
 -dave

On Feb 29, 2012, at 2:55 AM, Mark Chan wrote:

> Dear David,
>
> I still have problem for plot. The original data is very large and I made the annual average (by using CDO) for making the file smaller, as the attached file.
> The original file has rotated info as in the below, but the CDO-processed file doesn't have this info. Could you please help have a look at the data and give a plot suggestion?
>
> Thanks so much!
> Mark
>
>
> char rotated_pole ;
> rotated_pole:long_name = "coordinates of the rotated North Pole" ;
> rotated_pole:grid_mapping_name = "rotated_latitude_longitude" ;
> rotated_pole:grid_north_pole_latitude = 39.25f ;
> rotated_pole:grid_north_pole_longitude = -162.f ;
>
>
> From: David Brown <dbrown@ucar.edu>
> To: Mark Chan <cym263@yahoo.com>
> Cc: NCL Helpline <ncl-talk@ucar.edu>
> Sent: Tuesday, February 28, 2012 6:18 PM
> Subject: Re: transform a projection into regular lat-lon
>
> Hi Mark,
> Since the NCL is looking for the center longitude and you have the north pole, I think you should try setting mpCenterLatF to 39.25 - 90. Let us know if that does not produce a reasonable plot.
> -dave
>
>
> On Feb 28, 2012, at 6:11 AM, Mark Chan wrote:
>
>> Dear Dennis,
>>
>> Thanks a lot for your message. I wonder whether I could find the input data for the example in the website, so I could compare it with my data.
>> For instance, how could I get the parameters as in the below since my data has something like "grid_north_pole_latitude : 39.25".
>>
>> res@mpCenterLonF = lon2d@Longitude_of_southern_pole
>> res@mpCenterLatF = lon2d@Latitude_of_southern_pole + 90
>> Thanks a lot again!
>>
>> Mark
>> From: Dennis Shea <shea@ucar.edu>
>> To: Mark Chan <cym263@yahoo.com>
>> Cc: "ncl-talk@ucar.edu" <ncl-talk@ucar.edu>
>> Sent: Monday, February 27, 2012 5:39 PM
>> Subject: Re: transform a projection into regular lat-lon
>>
>> Does
>> http://www.ncl.ucar.edu/Applications/rotatedltln.shtml
>> answer your question. Please read the text.
>>
>> Good Luck
>>
>> On 2/27/12 3:31 AM, Mark Chan wrote:
>> > Dear NCL users,
>> >
>> > I have a model output file having info as in the below. I was told it is
>> > "rotated projection" (I don't know exactly what it is).
>> > Could any one help give me a suggestion how to transform this data into
>> > regular lat-lon projection? The main issue is how to define its
>> > projection when reading it with NCL?
>> >
>> > Thanks so much in advance!
>> > Mark Chan
>> >
>> > ----------------------Data file info ------------------------
>> > dimensions:
>> > ncl_scalar = 1
>> > rlat = 92
>> > rlon = 108
>> > time = 87648 // unlimited
>> > height_2m = 1
>> > variables:
>> > double time ( time )
>> > standard_name : time
>> > units : seconds since 1989-01-01 00:00:00
>> > calendar : standard
>> > float rlon ( rlon )
>> > standard_name : grid_longitude
>> > units : degrees
>> > float rlat ( rlat )
>> > standard_name : grid_latitude
>> > units : degrees
>> > float lon ( rlat, rlon )
>> > standard_name : longitude
>> > units : degrees_east
>> > float lat ( rlat, rlon )
>> > standard_name : latitude
>> > units : degrees_north
>> > float height_2m ( height_2m )
>> > long_name : height above surface
>> > units : m
>> > character rotated_pole ( ncl_scalar )
>> > long_name : coordinates of the rotated North Pole
>> > grid_mapping_name : rotated_latitude_longitude
>> > grid_north_pole_latitude : 39.25
>> > grid_north_pole_longitude : -162
>> > short tas ( time, height_2m, rlat, rlon )
>> > standard_name : air_temperature
>> > long_name : 2m temperature
>> > units : K
>> > coordinates : lon lat
>> > scale_factor : 0.004940663
>> > add_offset : 161.8932
>> > ====================================
>> >
>> > -----------------Its grids info is
>> > as-----------------------------------------------------
>> > rlon = -10.445, -10.335, -10.225, -10.115, -10.005, -9.895, -9.785, -9.675,
>> > -9.565, -9.455, -9.345, -9.235, -9.125, -9.015, -8.905, -8.795, -8.685,
>> > -8.575, -8.465, -8.355, -8.245, -8.135, -8.025, -7.915, -7.805, -7.695,
>> > -7.585, -7.475, -7.365, -7.255, -7.145, -7.035, -6.925, -6.815, -6.705,
>> > -6.595, -6.485, -6.375, -6.265, -6.155, -6.045, -5.935, -5.825, -5.715,
>> > -5.605, -5.495, -5.385, -5.275, -5.165, -5.055, -4.945, -4.835, -4.725,
>> > -4.615, -4.505, -4.395, -4.285, -4.175, -4.065, -3.955, -3.845, -3.735,
>> > -3.625, -3.515, -3.405, -3.295, -3.185, -3.075, -2.965, -2.855, -2.745,
>> > -2.635, -2.525, -2.415, -2.305, -2.195, -2.085, -1.975, -1.865, -1.755,
>> > -1.645, -1.535, -1.425, -1.315, -1.205, -1.095, -0.985, -0.875, -0.765,
>> > -0.655, -0.545, -0.435, -0.325, -0.215, -0.105, 0.005, 0.115, 0.225,
>> > 0.335, 0.445, 0.555, 0.665, 0.775, 0.885, 0.995, 1.105, 1.215, 1.325 ;
>> >
>> > rlat = -8.855, -8.745, -8.635, -8.525, -8.415, -8.305, -8.195, -8.085,
>> > -7.975, -7.865, -7.755, -7.645, -7.535, -7.425, -7.315, -7.205, -7.095,
>> > -6.985, -6.875, -6.765, -6.655, -6.545, -6.435, -6.325, -6.215, -6.105,
>> > -5.995, -5.885, -5.775, -5.665, -5.555, -5.445, -5.335, -5.225, -5.115,
>> > -5.005, -4.895, -4.785, -4.675, -4.565, -4.455, -4.345, -4.235, -4.125,
>> > -4.015, -3.905, -3.795, -3.685, -3.575, -3.465, -3.355, -3.245, -3.135,
>> > -3.025, -2.915, -2.805, -2.695, -2.585, -2.475, -2.365, -2.255, -2.145,
>> > -2.035, -1.925, -1.815, -1.705, -1.595, -1.485, -1.375, -1.265, -1.155,
>> > -1.045, -0.935, -0.825, -0.715, -0.605, -0.495, -0.385, -0.275, -0.165,
>> > -0.055, 0.055, 0.165, 0.275, 0.385, 0.495, 0.605, 0.715, 0.825, 0.935,
>> > 1.045, 1.155 ;
>> >
>> >
>> >
>> >
>> > _______________________________________________
>> > ncl-talk mailing list
>> > List instructions, subscriber options, unsubscribe:
>> > http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>
>>
>> _______________________________________________
>> ncl-talk mailing list
>> List instructions, subscriber options, unsubscribe:
>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>
>
>
> <Rotated_2009.nc>

_______________________________________________
ncl-talk mailing list
List instructions, subscriber options, unsubscribe:
http://mailman.ucar.edu/mailman/listinfo/ncl-talk
Received on Wed Feb 29 15:49:57 2012