Re: create time in netcdf variable

From: Dennis Shea <shea_at_nyahnyahspammersnyahnyah>
Date: Wed, 16 Jul 2008 12:21:04 -0600

As Jamie has stated and the output print statements show,
you are overwriting the information each loop iteration.

How is NCL to 'know' that you want a file with 8 time steps on it?

[a]
You could create a single netCDF file for each time and use (say) ncrcat
to concatenate the files.

[b]
You can preallocate arrays and then after the loop write to the file once.
Something like:

    ntim = 8
    nlat = 480
    mlon = 1440
 
    yyyymmdd = year*10000 + month*100 + day
    time = yyyymmdd*100 + ispan(0,21,3)
    time!0 = "time"
    time_at_units = "yyyymmddhh"
    time&time = time
    print(time)

    CMORPH = new ( (/ntim,nlat,mlon/), "float")
    pc_combined_MW = CMORPH

    fName = "./20060901_3hr-025deg_cpc+comb"
 
   do i = 0, 14,2
       pc_combined_MW(i/2,:,:) =
fbindirread(fName,i,(/ntim,nlat,mlon/),"float")
       CMORPH(i/2,:,:) = fbindirread(fName, i+1,(/ntim,nlat,mlon/),"float")
   end do

     CMORPH!0 = "time"
     CMORPH!1 = "lat"
     CMORPH!2 = "lon"
     CMORPH&time = time
     CMORPH&lat = lat
     CMORPH&lon = lon
     CMORPH_at_long_name = "CMORPH"
     CMORPH_at_units = "mm/hr"

; same for pc_combined_MW

    a = addfile("sample.nc","c") ; write netCDF file
    a_at_title = "1 day of daily CMORPH precipitation data"
    a_at_source =
"ftp://ftp.cpc.ncep.noaa.gov/precip/global_CMORPH/3-hourly_025deg"
    filedimdef(a,"time",-1,True) ; make time an UNLIMITED
 
     a->CMORPH = CMORPH
     a->COMB_MW = pc_combined_MW
 end

Erik Noble wrote:
> Hi.
> You suggest eliminating the do loop, correct?
> -Erik
>
> On Wed, Jul 16, 2008 at 12:20 PM, Jamie Scott <James.D.Scott_at_noaa.gov> wrote:
>
>> Eric,
>> I think the problem is that the 2 variables you are writing to the netcdf
>> file
>> only contain one time step. Even though you are looping through time
>> and writing 8 times, I think you are just overwriting the 1st time step in
>> the
>> netcdf file each time.
>> Try making the variables you write (cpc_combined_mw, cmorph and time)
>> such that they contain all 8 time steps and write them only once.
>>
>> Jamie Scott
>>
>> NOAA/ESRL/PSD
>>
>> james.d.scott_at_noaa.gov
>>
>> On Jul 16, 2008, at 9:58 AM, ncl-talk-request_at_ucar.edu wrote:
>>
>> May I have some help? This is an update my earlier request for help
>> with getting time displayed in my netcdf file. I updated my code fromearlie
>> till getting incorrect time. When I do
>> "ncdump -h" on the my output netcdf file, I don't get the proper time
>> that should reflect 3-hourly intervals for 1 day.
>> (It says time = UNLIMITED ; // (1 currently). it should be time =
>> UNLIMITED ; // (8 currently)).
>> I'm reading in a binary file that I'm told is composed of 16 direct
>> access binary ("big_endian") records, which are 2 variables at
>> 3-hourly ntervals for 1 day, basically 8 pairs.
>>
>> I searched throughout previous posts about time coordinates before
>> posting this question ncl-talk. Its not clear whether i need to resort
>> to making up this variable (i.e. specifically make a variable time =
>> year*10000 + month*100 + day...etc) or if Its something even more
>> simple that I am overlooking.
>>
>> Could I have please have some advice on how to fix this? I have my
>> screen readouts and ncl code below.
>> -Erik
>>
>> _______________________________________________
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>>
>>
>>
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-- 
======================================================
Dennis J. Shea                  tel: 303-497-1361    |
P.O. Box 3000                   fax: 303-497-1333    |
Climate Analysis Section                             |
Climate & Global Dynamics Div.                       |
National Center for Atmospheric Research             |
Boulder, CO  80307                                   |
USA                        email: shea 'at' ucar.edu |
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Received on Wed Jul 16 2008 - 12:21:04 MDT

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