[ncl-talk] Assign lat lon cordinates to polar stereographic coordinate

[Sourav Chatterjee]

Thanks alot Mary for the explanation.

Actually I need to do some area averaging for which I have the lat lon information e.g say, surface temperature averaged over 40-50N and -30:-10E. How to perform this spatial averaging with this temperature(time,depth,y,x) variable?

Thanks
Sourav
________________________________
From: Mary Haley<mailto:haley at ucar.edu>
Sent: ‎12-‎09-‎2016 23:38
To: Sourav Chatterjee<mailto:srvsxc at outlook.com>
Cc: ncl-talk at ucar.edu<mailto:ncl-talk at ucar.edu>
Subject: Re: [ncl-talk] Assign lat lon cordinates to polar stereographic coordinate

Sourav,

I'm not sure what you mean by "converting my variable".

Since your latitude and longitude arrays are two-dimensional, you cannot associate them with "temperature" in the same way that "y" and "x" are currently associated with "temperature" as coordinate variables. This is a NetCDF limitation that requires that coordinate variables be one-dimensional and the same length as the dimension they represent.

You already have a "coordinates" *attribute* associated with "temperature", that indicates which variables represent the lat/lon arrays for your data:

        temperature:coordinates = "longitude latitude" ;

This is how we would normally suggest that you "associate" 2D lat/lon arrays with a variable on a NetCDF file, so really, your "temperature" variable looks pretty good as it is.

--Mary


On Fri, Sep 9, 2016 at 4:19 AM, Sourav Chatterjee <srvsxc at outlook.com<mailto:srvsxc at outlook.com>> wrote:

Hi all


I want convert my variable (temperature) to temperature (time,depth,lat,lon) from temperature(time,depth,x,y)



here is how it looks like now.


Any help!


Thanks


dimensions:
    depth = 12 ;
    time = UNLIMITED ; // (288 currently)
    x = 428 ;
    y = 403 ;
variables:
    int stereographic ;
        stereographic:grid_mapping_name = "polar_stereographic" ;
        stereographic:latitude_of_projection_origin = 90. ;
        stereographic:longitude_of_projection_origin = -45. ;
        stereographic:scale_factor_at_projection_origin = 1. ;
        stereographic:straight_vertical_longitude_from_pole = -45. ;
        stereographic:false_easting = 0. ;
        stereographic:false_northing = 0. ;
    float x(x) ;
        x:axis = "X" ;
        x:standard_name = "projection_x_coordinate" ;
        x:units = "100  km" ;
    float y(y) ;
        y:standard_name = "projection_y_coordinate" ;
        y:axis = "Y" ;
        y:units = "100  km" ;
    float depth(depth) ;
        depth:long_name = "depth" ;
        depth:units = "m" ;
        depth:standard_name = "depth" ;
        depth:positive = "down" ;
        depth:axis = "Z" ;
    double time(time) ;
        time:units = "hour since 1950-1-1T00:00:00Z" ;
        time:long_name = "forecast time" ;
    float longitude(y, x) ;
        longitude:standard_name = "longitude" ;
        longitude:units = "degrees_east" ;
    float latitude(y, x) ;
        latitude:standard_name = "latitude" ;
        latitude:units = "degrees_north" ;
    short temperature(time, depth, y, x) ;
        temperature:_FillValue = -32767s ;
        temperature:missing_value = -32767s ;
        temperature:add_offset = 23.5 ;
        temperature:scale_factor = 0.000808839239385893 ;
        temperature:units = "Celsius" ;
        temperature:standard_name = "sea_water_potential_temperature" ;
        temperature:grid_mapping = "stereographic" ;
        temperature:coordinates = "longitude latitude" ;
        temperature:cell_methods = "area: mean" ;

// global attributes:
        :title = "Arctic Ocean Physics Reanalysis (1991-2014), 12.5km monthly mean (dataset-ran-arc-myoceanv2-be)" ;
        :institution = "NERSC, Thormoehlens gate 47, N-5006 Bergen, Norway" ;
        :history = "20160112:Created by program hyc2proj, version V0.3" ;
        :source = "NERSC-HYCOM model fields" ;
        :references = "http://topaz.nersc.no" ;
        :field_type = "Files based on file type nersc_weekly" ;
        :Conventions = "CF-1.4" ;
        :field_date = "2014-11-15" ;
        :bulletin_date = "2014-11-15" ;
}


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