Hi Olumide,
Since I responded to a separate emailed version of this question, I'm including
that response here, so the question and answer can be found with a search of
our support archives. Below that, Dennis Shea's detailed response is included.
> I have weather datasets from the TRMM 3-hourly data in Netcdf format. I am
> looking for ways to merge these multiple netcdf files that have same
> variables and are in sequential time periods. Such as 3B42.199801.3hr_V7.nc,
> 3B42.199803.3hr_V7.nc, 3B42.199802.3hr_V7.nc.
>
> I would like to merge these files together with time component added in the
> file. I would appreciate your suggestions.
>
> I would also like you to help me CDO scripts to merge these Netcdf files
> together.
>
> Thanks!
Although CDO scripts might be able to do what you want, the NCO tool named
ncrcat should work,
assuming each input file has a time dimension and time is a record dimension.
Dennis Shea, an expert at processing TRMM data, might be able to provide more
advice about using
NCL or NCO tools to merge the 3-hourly TRMM files. I'm Cc:ing him in this
reply.
--Russ
Dennis Shea's reply:
[1] Assuming that the ' 3B42.199801.3hr_V7.nc ' has an unlimited time
dimension, the NCO operator 'ncrcat' is the recommended tool to
concatenate multiple files. I am not an expert on the CDO but, in
my opinion, the NCO are better suited for concatenating files than
the CDO.
%> ncrcat -O -h 3B42.1998*.3hr_V7.nc V7_3hr.3B42.1998.nc
would efficiently create one file with all variables. Note ... a
file containing all 3hrly data for one year would be *huge*. There
would be 8*365 time steps on a 400x1440 grid for 6 variables!
Figure it out for yourself.
[2] One month of 3-hrly TRMM precip contains (say) 248 (8*31) time
steps and is about 571MB. This includes *only* precipitation and
no other variables. NO: 'err', 'source', 'hqp' , 'irp',
'satobstime' variables.
[3] How do I know? I created monthly files containing the
precipitation variable *only*. A modeling project I am working on
required some additional information so I used an NCL script to
perform some tasks and then invoked an NCO operator from with ine
NCL script to create the files. A sample dump follows:
%> ncdump -h 3B42.200301.3hr_V7
netcdf \3B42.200301.3hr_V7 {
dimensions:
time = UNLIMITED ; // (248 currently)
lat = 400 ;
lon = 1440 ;
variables:
double time(time) ;
time:calendar = "gregorian" ;
time:units = "hours since 1997-01-01 00:00:0.0" ;
double lat(lat) ;
lat:long_name = "Latitude" ;
lat:units = "degrees_north" ;
double lon(lon) ;
lon:long_name = "Longitude" ;
lon:units = "degrees_east" ;
int date(time) ;
date:units = "yyyymmdd" ;
date:long_name = "current date" ;
int datesec(time) ;
datesec:units = "seconds" ;
datesec:long_name = "current seconds of current date" ;
int yyyymmddhh(time) ;
yyyymmddhh:units = "current date" ;
yyyymmddhh:long_name = "current date with hh" ;
float precip(time, lat, lon) ;
precip:avg_period = "0000-00-00 01:00:00" ;
precip:delta_t = "0000-00-00 03:00:00" ;
precip:comments = "Unknown1 variable comment" ;
precip:long_name = "precipitation" ;
precip:units = "" ;
precip:time_statistic = "instantaneous" ;
precip:missing_value = -9999.9f ;
precip:_FillValue = -9999.9f ;
// global attributes:
:creation_date = "Mon Mar 3 09:28:42 MST 2014" ;
:Conventions = "None" ;
:time_info = "\n",
"NASA:
\n",
"The 0Z in the filename is the mid point of a 3 hour
\n",
"interval beginning at 22:30Z (1/14/1998) and ending at
1:30Z (1/15/1998).\n",
"The precipitation is the average rain rate for this
time period. \n",
"" ;
:source_URL = "\n",
"http://mirador.gsfc.nasa.gov/cgi-bin/mirador/collectionlist.pl?keyword=TRMM\n";,
"" ;
:source_data = "\n",
"Download netCDF from NASA MIRADOR: Search for:\n",
"TRMM 3-Hourly 0.25 deg. TRMM and Other-GPI Calibration
Rainfall Data (TRMM_3B42)\n",
"" ;
:title = "TRMM: 3B42: V7" ;
}
[4] gzip'd versions of these files are available via ftp. Each file is
about 51MB
ftp ftp.cgd.ucar.edu
anonymous
email
cd /archive/PRECIP
prompt
mget 3B42.*.3hr_V7.nc.gz
quit
If you want only specific years and or months. you can use linux/unix
'wild' notation
There is also a simgle file which contans *monthly mean* precip
TRMM_3B43V7.19980101-20140201.nc.gz
============================================
Russ Rew UCAR Unidata Program
address@hidden http://www.unidata.ucar.edu
Ticket Details
===================
Ticket ID: SIY-529931
Department: Support netCDF
Priority: Normal
Status: Closed
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