Re: transform a projection into regular lat-lon

From: Dennis Shea <shea_at_nyahnyahspammersnyahnyah>
Date: Thu Mar 01 2012 - 08:57:54 MST

You must interpolate the data.

On 3/1/12 3:28 AM, Mark Chan wrote:
> Dear Dave,
>
> Thanks so much. What you did is so helpful and I don't know how to
> express my gratitude!
> I feel embarrassed to ask the further question: How is it possible to
> output an new data file with spatial grids as "0.1/0.1" lat-lon degree
> for the domain as below.
>
> res@mpMinLatF = 46 ; Austria limits
> res@mpMaxLatF = 50
> res@mpMinLonF = 9
> res@mpMaxLonF = 18
>
> I want to extract the data of a specific area for other application.
>
> With my best regards,
> Mark
>
>
> ------------------------------------------------------------------------
> *From:* David Brown <dbrown@ucar.edu>
> *To:* Mark Chan <cym263@yahoo.com>
> *Cc:* NCL Helpline <ncl-talk@ucar.edu>
> *Sent:* Wednesday, February 29, 2012 11:49 PM
> *Subject:* Re: [ncl-talk] 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 <mailto:dbrown@ucar.edu>>
>> *To:* Mark Chan <cym263@yahoo.com <mailto:cym263@yahoo.com>>
>> *Cc:* NCL Helpline <ncl-talk@ucar.edu <mailto:ncl-talk@ucar.edu>>
>> *Sent:* Tuesday, February 28, 2012 6:18 PM
>> *Subject:* Re: [ncl-talk] 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 <mailto:shea@ucar.edu>>
>>> *To:* Mark Chan <cym263@yahoo.com <mailto:cym263@yahoo.com>>
>>> *Cc:* "ncl-talk@ucar.edu <mailto:ncl-talk@ucar.edu>"
>>> <ncl-talk@ucar.edu <mailto:ncl-talk@ucar.edu>>
>>> *Sent:* Monday, February 27, 2012 5:39 PM
>>> *Subject:* Re: [ncl-talk] 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 ;
>>> >
>>> >
>>> >
>>> >
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>>
>>
>>
>> <Rotated_2009.nc>
>
>
>
>
>
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Received on Thu Mar 1 08:58:03 2012

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