create "time" in netcdf file from Erik Noble on 2008-07-16 (ncl-talk 2008 archive)

From: Erik Noble <enoble_at_nyahnyahspammersnyahnyah>
Date: Wed, 16 Jul 2008 11:58:10 -0400

Dear NCL world,
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 from
earlier suggestions, but I am still 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

My ncdump -h of netcdf file:
ENOBLE_at_ATHENA: /usr/people/enoble> ncdump -h sample.nc
netcdf sample {
dimensions:
        time = UNLIMITED ; // (1 currently)
        lat = 480 ;
        lon = 1440 ;
variables:
        float COMB_MW(time, lat, lon) ;
                COMB_MW:units = "mm/hr" ;
                COMB_MW:long_name = "merged microwave precipitation" ;
        float lat(lat) ;
                lat:units = "degrees_north" ;
        float lon(lon) ;
                lon:units = "degrees_east" ;
        float CMORPH(time, lat, lon) ;
                CMORPH:units = "mm/hr" ;
                CMORPH:long_name = "CMORPH" ;

// global attributes:
:title = "1 day of daily CMORPH precipitation data" ;
:source =
"ftp://ftp.cpc.ncep.noaa.gov/precip/global_CMORPH/3-hourly_025deg" ;

=======
ncl code
=======

; NCL script that reads in ONE NOAA CMORH precipitation binary file
; 16 direct access binary ("big_endian") records, which are 2
variables at 3-hourly
; intervals for 1 day
;************************************************
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_code.ncl"
load "$NCARG_ROOT/lib/ncarg/nclscripts/csm/gsn_csm.ncl"
;************************************************
begin
    a = addfile("sample.nc","c") ; write netCDF file
    a_at_title = "1 day of daily CMORPH precipitation data"
    a@source = "ftp://ftp.cpc.ncep.noaa.gov/precip/global_CMORPH/3-hourly_025deg"
    filedimdef(a,"time",-1,True) ; make time an UNLIMITED
dimension, always recommended

    ;===================
    ; create time variable
    ;===================
; time = year*10000 + month*100 + day
; time_at_units = "yyyymmdd"

    ;=============================
    ; create lat and long coordinate variables
    ;============================

    nlat = 480
    mlon = 1440
    lat = 59.875 - ispan(0,nlat-1,1)*0.25
    lon = 0.125 + ispan(0,mlon-1,1)*0.25
    lat!0 = "lat"
    lat&lat = lat
    lat_at_units = "degrees_north"

    lon!0 = "lon"
    lon&lon = lon
    lon_at_units = "degrees_east"

   setfileoption ("bin", "ReadByteOrder", "BigEndian")
   ntime = 1
   do i = 0, 14,2 ; CMORPH binary file contains 16
records. NCL starts at counting at 0
     cpc_combined_MW = fbindirread
("./20060901_3hr-025deg_cpc+comb",i,(/ntime,480,1440/),"float")
     CMORPH = fbindirread
("./20060901_3hr-025deg_cpc+comb",i+1,(/ntime,480,1440/),"float")

    ;=============================
    ; name dimensions of variables
    ;============================
     cpc_combined_MW!0 = "time"
     cpc_combined_MW!1 = "lat"
     cpc_combined_MW!2 = "lon"
    ; cpc_combined_MW&time = time
     cpc_combined_MW&lat = lat
     cpc_combined_MW&lon = lon
     cpc_combined_MW_at_long_name = "merged microwave precipitation"
     cpc_combined_MW_at_units = "mm/hr"
     print ("====== Binary Record= "+(i+1) +"/ NCL Record Counter
"+(i)+" ======")
     printVarSummary(cpc_combined_MW)

     CMORPH!0 = "time"
     CMORPH!1 = "lat"
     CMORPH!2 = "lon"
     CMORPH&lat = lat
     CMORPH&lon = lon
     CMORPH_at_long_name = "CMORPH"
     CMORPH_at_units = "mm/hr"
     print ("====== Binary Record= "+(i+2) +"/ NCL Record Counter
"+(i+1)+" ======")
     printVarSummary(CMORPH)

    a->COMB_MW = cpc_combined_MW
    a->CMORPH = CMORPH
   end do
end

================================
My screen readout when executing NCL:
================================
ENOBLE_at_ATHENA: /usr/people/enoble> ncl bin3.ncl
Copyright (C) 1995-2007 - All Rights Reserved
University Corporation for Atmospheric Research
NCAR Command Language Version 4.3.1
The use of this software is governed by a License Agreement.
See http://www.ncl.ucar.edu/ for more details.
(0) ====== Binary Record= 1/ NCL Record Counter 0 ======

Variable: cpc_combined_MW
Type: float
Total Size: 2764800 bytes
            691200 values
Number of Dimensions: 3
Dimensions and sizes: [time | 1] x [lat | 480] x [lon | 1440]
Coordinates:
            lat: [59.875..-59.875]
            lon: [0.125..359.875]
Number Of Attributes: 2
  units : mm/hr
  long_name : merged microwave precipitation
(0) ====== Binary Record= 2/ NCL Record Counter 1 ======

Variable: CMORPH
Type: float
Total Size: 2764800 bytes
            691200 values
Number of Dimensions: 3
Dimensions and sizes: [time | 1] x [lat | 480] x [lon | 1440]
Coordinates:
            lat: [59.875..-59.875]
            lon: [0.125..359.875]
Number Of Attributes: 2
  units : mm/hr
  long_name : CMORPH
ENOBLE_at_ATHENA: /usr/people/enoble>
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Received on Wed Jul 16 2008 - 09:58:10 MDT

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