[Support #LXJ-482685]: to read time dimension

> Hi
> 
> I am programming to read NAM-CONUS-12km data from NetCDF file.  For the "time"
> dimension, the name is "time1" for some variables and "time" for some other
> variables. So, I cannot inquire variable id by giving a fixed name.  For
> example, I cannot call such as
> 
> NetCDF.nc_inq_varid(ncid, "time1", varid_time1)
> 
> as the name might be "time" instead of "time1".
> 
> I wonder what '1' means in "time1" and how you would suggest to program to get
> the variable id of the time dimension.  The attached are two examples of the
> meta data with different dimension names for the time.
> 
> Thanks,
> Thiha Min.
> 
> 
> Center for Research in Water Resources
> University of Texas at Austin
> 
> ---------example1 of NetCDF meta data for Total_precipitation variable;-----
> ---------it uses the name time1-------------------------------------
> 
> netcdf NAM_CONUS_12km_20070302_1800.grib2 {
> dimensions:
> time1 = 12 ;
> y = 11 ;
> x = 2 ;
> variables:
> float Total_precipitation(time1, y, x) ;
> Total_precipitation:units = "kg m-2" ;
> Total_precipitation:long_name = "Total precipitation @ surface" ;
> Total_precipitation:missing_value = -9999.f ;
> Total_precipitation:grid_mapping = "Lambert_Conformal" ;
> Total_precipitation:GRIB_param_discipline = "Meteorological_products" ;
> Total_precipitation:GRIB_param_category = "Moisture" ;
> Total_precipitation:GRIB_param_name = "Total_precipitation" ;
> Total_precipitation:GRIB_param_id = 2, 0, 1, 8 ;
> Total_precipitation:GRIB_product_definition_type = "Average, accumulation,
> extreme values or other statistically processed value at a horizontal level" ;
> Total_precipitation:GRIB_level_type = 1 ;
> int time1(time1) ;
> time1:long_name = "forecast time" ;
> time1:units = "hours since 2007-03-02T18:00:00Z" ;
> time1:GRIB_orgReferenceTime = "2007-03-02T18:00:00Z" ;
> time1:GRIB2_significanceOfRTName = "Start of forecast" ;
> time1:_CoordinateAxisType = "Time" ;
> 
> ----------------------------------------------------------------------------
> --------------example2 of NetCDF metadata for Precipitable_water;-------
> ------------- it uses the name "time"---------------------------
> 
> netcdf NAM_CONUS_12km_20070329_1200.grib2 {
> dimensions:
> time = 26 ;
> y = 1 ;
> x = 1 ;
> variables:
> float Precipitable_water(time, y, x) ;
> Precipitable_water:units = "kg m-2" ;
> Precipitable_water:long_name = "Precipitable water @ entire_atmosphere" ;
> Precipitable_water:missing_value = -9999.f ;
> Precipitable_water:grid_mapping = "Lambert_Conformal" ;
> Precipitable_water:GRIB_param_discipline = "Meteorological_products" ;
> Precipitable_water:GRIB_param_category = "Moisture" ;
> Precipitable_water:GRIB_param_name = "Precipitable_water" ;
> Precipitable_water:GRIB_param_id = 2, 0, 1, 3 ;
> Precipitable_water:GRIB_product_definition_type = "Analysis/forecast at
> horizontal level/layer" ;
> Precipitable_water:GRIB_level_type = 200 ;
> int time(time) ;
> time:long_name = "forecast time" ;
> time:units = "hours since 2007-03-29T12:00:00Z" ;
> time:GRIB_orgReferenceTime = "2007-03-29T12:00:00Z" ;
> time:GRIB2_significanceOfRTName = "Start of forecast" ;
> time:_CoordinateAxisType = "Time" ;
> ----------------------------------------------------------
> 
> 

Howdy Thiha!

I'm sorry, but you will have to ask the producer of the data files why they 
sometimes use "time" and sometimes "time1."

As far as netCDF is concerned, a time dimension may have any name at all. 
NetCDF doesn't use the names of dimensions in any way, it just stores them for 
user convenience.

Thanks,

Ed

Ticket Details
===================
Ticket ID: LXJ-482685
Department: Support netCDF
Priority: Normal
Status: Closed