Re: [netcdfgroup] Questions about NetCDF file - How can I interpret the nc file

The information you need is there in the variable information:

 short Wind_U(time, lat, lon) ;
  Wind_U:long_name = "Wind U Component" ;
  Wind_U:units = "m/s" ;
  Wind_U:scale_factor = 0.01f ;
  Wind_U:valid_range = -100s, 100s ;
  Wind_U:missing_value = -9999s ;
  Wind_U:_FillValue = -9999s ;
  Wind_U:coordinate = "lon lat" ;

So the values are in m/s but need a scale factor of 0.01 applied because it is 
stored as a short integer rather than a float. Thus 155 is 1.55 m/s. 

As for the ordering, these are in the C convention (opposite of Fortran) 'time' 
is the slowest index, whereas 'lon' is stride one. [In the Fortran interface, 
the arrays are automatically switched to (lon, lat, time)]

Thus:

Wind_U(time=0, lat=-90, lon=0) = 155  -> 1.55 m/s
Wind_U(time=0, lat=-90, lon=0.5) = 158 -> 1.58 m/s
Wind_U(time=0, lat=-90, lon=1.0) = 161 -> 1.61 m/s

etc.

-- Ted
__________________________________________________________
| Edward Mansell <address@hidden>
| National Severe Storms Laboratory
|--------------------------------------------------------------
| "The contents of this message are mine personally and
| do not reflect any position of the U.S. Government or NOAA."
|--------------------------------------------------------------


I suggest getting a viewing tool like ncview to peruse the data graphically.

On May 20, 2015, at 9:58 PM, 동희 <address@hidden> wrote:

> Dear NetCDF suppot team
> 
>  
> Hello
> 
> I am DH from Korea.
> 
> I am going to use netcdf file soon to get the weather information at my 
> company.
> 
> But the problem is I am the first one in my company so don't know how to 
> interpret the nc file.
> 
> (I can just convert to txt file with ncdump, and read the letters...)
> 
>  
> below is the netcdf file which I should interpret...(it contains global wind 
> information)
> 
>  
> ========================================================================================
> 
> netcdf GFS20150520 {
> dimensions:
>  lon = 720 ;
>  lat = 361 ;
>  time = UNLIMITED ; // (57 currently)
> variables:
>  float lat(lat) ;
>   lat:long_name = "Latitude" ;
>   lat:units = "degrees_north" ;
>   lat:missing_value = -99999.f ;
>   lat:_FillValue = -99999.f ;
>  float lon(lon) ;
>   lon:long_name = "Longitude" ;
>   lon:units = "degrees_east" ;
>   lon:missing_value = -99999.f ;
>   lon:_FillValue = -99999.f ;
>  int time(time) ;
>   time:long_name = "forecast time" ;
>   time:units = "minutes since 2015-05-20 00:00" ;
>   time:standard_name = "time" ;
>   time:reference = "UTC" ;
>   time:missing_value = -99999 ;
>   time:_FillValue = -99999 ;
>  short Wind_U(time, lat, lon) ;
>   Wind_U:long_name = "Wind U Component" ;
>   Wind_U:units = "m/s" ;
>   Wind_U:scale_factor = 0.01f ;
>   Wind_U:valid_range = -100s, 100s ;
>   Wind_U:missing_value = -9999s ;
>   Wind_U:_FillValue = -9999s ;
>   Wind_U:coordinate = "lon lat" ;
>  short Wind_V(time, lat, lon) ;
>   Wind_V:long_name = "Wind V Component" ;
>   Wind_V:units = "m/s" ;
>   Wind_V:scale_factor = 0.01f ;
>   Wind_V:valid_range = -100s, 100s ;
>   Wind_V:missing_value = -9999s ;
>   Wind_V:_FillValue = -9999s ;
>   Wind_V:coordinate = "lon lat" ;
> 
> // global attributes:
>   :title = "Environmental data" ;
>   :version = "1.0" ;
>   :institution = "ASA" ;
>   :Contact = "address@hidden" ;
>   :source = "NCEP NOAA" ;
>   :reference = "Created by DAN_GRIB2NC2 Version 3.0d at 05/20/15 18:14:53" ;
>   :default_view = "10 meter Wind U, Wind  V " ;
>   :netcdf_class = "2" ;
>   :netcdf_class_description = "Multi point, static, ..." ;
>   :time_var = "time" ;
>   :lat_var = "Lat" ;
>   :lon_var = "lon" ;
>   :view_style = "1" ;
>   :Conventions = "CF-1.0" ;
> data:
> lat = -90, -89.5, -89, -88.5, -88, -87.5, -87, -86.5, -86, -85.5, -85, 
>     -84.5, -84, -83.5, -83, -82.5, -82, -81.5, -81, -80.5, -80, -79.5, -79, 
>     -78.5, -78, -77.5, -77, -76.5, -76, -75.5, -75, -74.5, -74, -73.5, -73,
> 
> .....(oimt).....
> 
>  lon = 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 
>     8.5, 9, 9.5, 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 
>     16, 16.5, 17, 17.5, 18, 18.5, 19, 19.5, 20, 20.5, 21, 21.5, 22, 22.5, 23, 
>     23.5, 24, 24.5, 25, 25.5, 26, 26.5, 27, 27.5, 28, 28.5, 29, 29.5, 30,
> 
> .....(oimt).....
> 
> time = 0, 180, 360, 540, 720, 900, 1080, 1260, 1440, 1620, 1800, 1980, 2160, 
>     2340, 2520, 2700, 2880, 3060, 3240, 3420, 3600, 3780, 3960, 4140, 4320, 
>     4500, 4680, 4860, 5040, 5220, 5400, 5580, 5760, 5940, 6120, 6300, 6480, 
>     6660, 6840, 7020, 7200, 7380, 7560, 7740, 7920, 8100, 8280, 8460, 8640, 
>     8820, 9000, 9180, 9360, 9540, 9720, 9900, 10080 ;
> 
> Wind_U =
>   155, 158, 161, 164, 166, 168, 171, 175, 177, 179, 182, 184, 188, 190, 192, 
>     194, 197, 200, 203, 204, 207, 209, 212, 214, 216, 220, 222, 224, 227, 
>     229, 230, 233, 235, 237, 239, 241, 245, 247, 249, 251, 253, 255, 256,
> 
> .....(oimt).....
> 
> Wind_V =
>   -310, -309, -308, -307, -306, -304, -303, -301, -300, -298, -297, -295, 
>     -292, -291, -289, -287, -286, -284, -282, -281, -280, -278, -276, -274, 
>     -272, -270, -267, -265, -263, -262, -259, -257, -256, -254, -252, -250, 
>     -248, -246, -244, -241, -238, -236, -234, -232, -230, -228, -226, -223,
> 
> .....(oimt)
> 
> ========================================================================================
> 
>  
> For example, at the above file, the first value  of Wind_U, 155 is simply 
> meaning Wind_U(time, lat, lon)=Wind_U(0, -90, 0) ?
> 
> Then what about the second value of Wind_U, 158 ? Is that meaning Wind_U(0, 
> -90, 0.5) ? or Wind_U(180, -90, 0) ?
> 
> I am not sure this is right and I don't know about the order...
> 
>  
> Please reply me with brief explanation.
> 
> Thank you for reading.
> 
>  
> Best Regards
> 
> DH HAN
> 
>  
>  
> _______________________________________________
> netcdfgroup mailing list
> address@hidden
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