[gradsusr] Customize time axis
Jennifer Adams
jma at cola.iges.org
Wed May 28 19:30:39 EDT 2014
Ah, I see -- the problem is that your time axis isn't linear. The time increment is not constant -- it looks like your delta-T's (in hours) are 3, 3, 9, 9, 3, 3, 9, 9… I hate to say this, but GrADS won't handle that data file properly. The requirement of a linear time axis for gridded data is non-negotiable.
--Jennifer
On May 28, 2014, at 6:28 PM, Stefano Materia wrote:
>
> Hi Jennifer, sorry for my delayed reply.
>
> Why do you believe I need two axes? I only have one month (January), and I
> need to plot my 124 values (four per day at 8, 11, 14, 23). I really think
> I only need the axis for diurnal cycle at those specific times, but I'm
> not able to build it :)
>
> This is how the ncdump output looks like.
>
> ncdump -h tday_jan_daymean_1981-2010.nc
>
> netcdf tday_jan_daymean_1981-2010 {
> dimensions:
> longitude = 464 ;
> latitude = 201 ;
> time = UNLIMITED ; // (124 currently)
> variables:
> float longitude(longitude) ;
> longitude:standard_name = "longitude" ;
> longitude:long_name = "Longitude values" ;
> longitude:units = "degrees_E" ;
> longitude:axis = "X" ;
> float latitude(latitude) ;
> latitude:standard_name = "latitude" ;
> latitude:long_name = "Latitude values" ;
> latitude:units = "degrees_N" ;
> latitude:axis = "Y" ;
> double time(time) ;
> time:standard_name = "time" ;
> time:long_name = "Time in days" ;
> time:units = "days since 1980-01-01 08:00:00" ;
> time:calendar = "standard" ;
> short tn(time, latitude, longitude) ;
> tn:standard_name = "air_temperature" ;
> tn:long_name = "minimum temperature" ;
> tn:units = "Celsius" ;
> tn:add_offset = 0.f ;
> tn:scale_factor = 0.01f ;
> tn:_FillValue = -9999s ;
> tn:missing_value = -9999s ;
>
> ///
>
> and here is the output of the cdo command showinfo:
>
> cdo sinfo tday_jan_daymean_1981-2010.nc
> File format: netCDF
> -1 : Institut Source Ttype Levels Num Gridsize Num Dtype :
> Parameter ID
> 1 : unknown unknown instant 1 1 93264 1 I16 : -1
> Grid coordinates :
> 1 : lonlat > size : dim = 93264 nx = 464 ny = 201
> longitude : first = -40.375 last = 75.375 inc =
> 0.25 degrees_E
> latitude : first = 25.375 last = 75.375 inc =
> 0.25 degrees_N
> Vertical coordinates :
> 1 : surface : 0
> Time coordinate : 124 steps
> RefTime = 1980-01-01 08:00:00 Units = days Calendar = standard
> YYYY-MM-DD hh:mm:ss YYYY-MM-DD hh:mm:ss YYYY-MM-DD hh:mm:ss
> YYYY-MM-DD hh:mm:ss
> 1980-01-01 08:00:00 1980-01-01 11:00:00 1980-01-01 14:00:00
> 1980-01-01 23:00:00
> 1980-01-02 08:00:00 1980-01-02 11:00:00 1980-01-02 14:00:00
> 1980-01-02 23:00:00
> 1980-01-03 08:00:00 1980-01-03 11:00:00 1980-01-03 14:00:00
> 1980-01-03 23:00:00
> ..................................................................................
>
> ///
>
> Thanks very much for your help.
>
> Stefano
>
>
>> It sounds like what you really need are two axes -- a time axis with a
>> monthly increment, and another axis for the diurnal cycle at hours 8, 11,
>> 14, and 23 (E with a size of 4 would be useful for that). You can't plot
>> data at 12hourly and monthly increments in the same dimension. You will
>> probably need a full descriptor to get it right. What does the ncdump
>> output look like?
>> --Jennifer
>>
>>
>>
>> On May 20, 2014, at 1:32 PM, Stefano Materia wrote:
>>
>>> Dear all,
>>> I am facing a very annoying problem which I am not able to get around.
>>>
>>> I have netcdf data for the month of January, in which four temperatures
>>> are registered every day: at 8:00am, 11:00am, 2:00pm, 11:00pm.
>>> Basically,
>>> I have 124 values per month (31*4) specified at those exact times of the
>>> day, and this is how I want to graph them.
>>>
>>> RefTime = 1980-01-01 08:00:00 Units = days Calendar = standard
>>> YYYY-MM-DD hh:mm:ss YYYY-MM-DD hh:mm:ss YYYY-MM-DD hh:mm:ss
>>> YYYY-MM-DD
>>> hh:mm:ss
>>> 1980-01-01 08:00:00 1980-01-01 11:00:00 1980-01-01 14:00:00
>>> 1980-01-01
>>> 23:00:00
>>> 1980-01-02 08:00:00 1980-01-02 11:00:00 1980-01-02 14:00:00
>>> 1980-01-02
>>> 23:00:00
>>> 1980-01-03 08:00:00 1980-01-03 11:00:00 1980-01-03 14:00:00
>>> 1980-01-03
>>> 23:00:00
>>> 1980-01-04 08:00:00 1980-01-04 11:00:00 1980-01-04 14:00:00
>>> 1980-01-04
>>> 23:00:00
>>> ...
>>>
>>> When I try to plot this in Grads though, the time axis becomes
>>> disarranged: Grads splits the time steps every three hours
>>>
>>> ga-> q file
>>> File 1 :
>>> Descriptor: tday_jan_daymean_1981-2010.nc
>>> Binary: tday_jan_daymean_1981-2010.nc
>>> Type = Gridded
>>> Xsize = 464 Ysize = 201 Zsize = 1 Tsize = 124 Esize = 1
>>> Number of Variables = 1
>>> tn 0 t,y,x temperature
>>> ga-> set t 1
>>> Time values set: 1980:1:1:8 1980:1:1:8
>>> ga-> set t 2
>>> Time values set: 1980:1:1:11 1980:1:1:11
>>> ga-> set t 3
>>> Time values set: 1980:1:1:14 1980:1:1:14
>>> ga-> set t 4
>>> Time values set: 1980:1:1:17 1980:1:1:17
>>> ga-> set t 5
>>> Time values set: 1980:1:1:20 1980:1:1:20
>>> ga-> set t 6
>>> Time values set: 1980:1:1:20 1980:1:1:23
>>>
>>> This is not right, because I need my points to be centered at the time
>>> temperature are registered. Attached, a snapshot of the wrong plot
>>> coming
>>> out (for simplicity, I plotted up to the 16th timestep, which should be
>>> Jan 4, but it's not).
>>>
>>> I do not even find a way to specify this into the TDEF of a ctl file.
>>>
>>> Is anyone able to help me?
>>> Thanks a lot!
>>>
>>> --
>>> Stefano Materia, PhD
>>> Centro Euro-Mediterraneo sui Cambiamenti Climatici
>>> Viale Aldo Moro, 44 - 40127 Bologna
>>> Tel: +39 051 3782611
>>> Fax: +39 051 3782655
>>>
>>>
>>> <GradsPlot.png>_______________________________________________
>>> gradsusr mailing list
>>> gradsusr at gradsusr.org
>>> http://gradsusr.org/mailman/listinfo/gradsusr
>>
>> --
>> Jennifer M. Adams
>> Center for Ocean-Land-Atmosphere Studies (COLA)
>> 111 Research Hall, Mail Stop 2B3
>> George Mason University
>> 4400 University Drive
>> Fairfax, VA 22030
>>
>>
>>
>>
>>
>> _______________________________________________
>> gradsusr mailing list
>> gradsusr at gradsusr.org
>> http://gradsusr.org/mailman/listinfo/gradsusr
>>
>
>
> --
> Stefano Materia, PhD
> Centro Euro-Mediterraneo sui Cambiamenti Climatici
> Viale Aldo Moro, 44 - 40127 Bologna
> Tel: +39 051 3782611
> Fax: +39 051 3782655
>
> _______________________________________________
> gradsusr mailing list
> gradsusr at gradsusr.org
> http://gradsusr.org/mailman/listinfo/gradsusr
--
Jennifer M. Adams
Center for Ocean-Land-Atmosphere Studies (COLA)
111 Research Hall, Mail Stop 2B3
George Mason University
4400 University Drive
Fairfax, VA 22030
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