[ncl-talk] Reading Grib file in NCL

[Alan Brammer]

Not sure this is really an NCL question. 
You have to take the time to understand your data.  
You want temperature, so look through the filedump for things with a long_name “Temperature”


Here are two variables that are x metres above a surface.  

      float TMP_P0_L102_GLL0 ( lv_AMSL1, lat_0, lon_0 )
         center :	US National Weather Service - NCEP (WMC)
         production_status :	Operational products
         long_name :	Temperature
         units :	K
         _FillValue :	1e+20
         grid_type :	Latitude/longitude
         parameter_discipline_and_category :	Meteorological products, Temperature
         parameter_template_discipline_category_number :	( 0, 0, 0, 0 )
         level_type :	Specific altitude above mean sea level (m)
         forecast_time :	12
         forecast_time_units :	hours
         initial_time :	12/14/2015 (06:00)

      float TMP_P0_L103_GLL0 ( lv_HTGL2, lat_0, lon_0 )
         center :	US National Weather Service - NCEP (WMC)
         production_status :	Operational products
         long_name :	Temperature
         units :	K
         _FillValue :	1e+20
         grid_type :	Latitude/longitude
         parameter_discipline_and_category :	Meteorological products, Temperature
         parameter_template_discipline_category_number :	( 0, 0, 0, 0 )
         level_type :	Specified height level above ground (m)
         forecast_time :	12
         forecast_time_units :	hours
         initial_time :	12/14/2015 (06:00)


There are also these, which are specifically 2m above ground.

      float DPT_P0_L103_GLL0 ( lat_0, lon_0 )
         center :	US National Weather Service - NCEP (WMC)
         production_status :	Operational products
         long_name :	Dew point temperature
         units :	K
         _FillValue :	1e+20
         grid_type :	Latitude/longitude
         parameter_discipline_and_category :	Meteorological products, Temperature
         parameter_template_discipline_category_number :	( 0, 0, 0, 6 )
         level_type :	Specified height level above ground (m)
         level :	 2
         forecast_time :	12
         forecast_time_units :	hours
         initial_time :	12/14/2015 (06:00)

      float APTMP_P0_L103_GLL0 ( lat_0, lon_0 )
         center :	US National Weather Service - NCEP (WMC)
         production_status :	Operational products
         long_name :	Apparent Temperature
         units :	K
         _FillValue :	1e+20
         grid_type :	Latitude/longitude
         parameter_discipline_and_category :	Meteorological products, Temperature
         parameter_template_discipline_category_number :	( 0, 0, 0, 21 )
         level_type :	Specified height level above ground (m)
         level :	 2
         forecast_time :	12
         forecast_time_units :	hours
         initial_time :	12/14/2015 (06:00)


The point of ncl_filedump is so you can go through and find the variable you want. 

If you need more information than is contained, then go to the datasource and look for further documentation. 

When you find the variable, the variable name, is in the top line of each section in the firedamp.

e.g.
temp = inf->TMP_P0_L103_GLL0(:,:,:)  ; level, lat, lon, 


Good luck, 

Alan. 



> On 18 Dec 2015, at 10:07, Debasish Hazra <debasish.hazra5 at gmail.com> wrote:
> 
> Hi,
> 
>  I was trying to read GFS output (in grib) using NCL V.6.3 and ncl_filedump produced the variable names which is confusing to figure out what variable is what. I have attached ncl filedump output as text and an .idx file associated with the grib output. If I want to read 2m temperature as in there in .idx, which one of the variables read by ncl correspond to that ? Is there any way to figure out which is what from grib table to make sense of the ncl_filedump.
> 
> Sample gfs file is uploaded in the ftp. Any help is appreciated.
> 
> Thanks.
> Debasish. 
> <gfs.t06z.pgrb2.0p25.f012.idx.txt><vars.txt>_______________________________________________
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