Re: [ferret_users] Problem in preparing monthly climatology using multiple netcdf files

[Ansley Manke <ansley.b.manke@xxxxxxxx>]

Hi,
For our users who are familiar with NCO, are there tools there that 
would let Sreejith add a time dimension to the files and to the grids of 
the variables in the files?  If that's possible, then one could use a 
descriptor file and bypass the step of putting the data from all the 
files into one big monthly dataset and then forming the climatology from 
that.

If not, then the thing to do is described under the documentation under 
the topic "timestamp".  You define the final time axis as a monthly axis 
with the range of dates for the set of monthly files. Then define a 
variable which adds the dataset variable to a variable which is zero at 
all timesteps of the long monthly axis.  Write out just the timestep 
that corresponds to that file, appending to a monthly data file.

yes? define axis/t=1-jan-1871:31-dec-1881:1/units=months/edges monthtime
yes? let timestamp = 0* t[gt=monthtime]

(This makes an evenly-spaced axis - there are other ways to define 
monthly time axes. See entries under "axis" in the Ferret Users Guide 
index).

Then look at this,
http://ferret.pmel.noaa.gov/Ferret/documentation/users-guide/commands-reference/SAVE#timestamp

Where we'd open each file, define a variable that adds the file variable 
to "timestamp", and save/append/t= where t= specifies the appropriate 
month, to add them all to a file containing all of the months.

Finally, have a look at this FAQ on creating a climatology:
http://ferret.pmel.noaa.gov/Ferret/faq/how-do-i-calculate-climatologies-and-climatological-anomalies

Ansley

On 8/8/2012 12:24 PM, sreejith k.s wrote:
> Dear all,
> I am facing some problem in preparing monthly climatoloy using around
> 120 files covering 10 years.
>
> 1) Please see the files as shown below.
> SODA_2.2.4_187101.cdf
> SODA_2.2.4_187102.cdf
> SODA_2.2.4_187103.cdf
> ..................................................
> ..................................................
> ..................................................
> SODA_2.2.4_188012.cdf
>
> 2) For example, the "ncdump -h" command for one of these files will
> give the following result.
>
> netcdf SODA_2.2.4_187312 {
> dimensions:
>          lon = 720 ;
>          lat = 330 ;
>          depth = 40 ;
> variables:
>          float temp(depth, lat, lon) ;
>                  temp:long_name = "TEMPERATURE" ;
>                  temp:units = "deg. C" ;
>                  temp:_FillValue = -9.99e+33f ;
>          float salt(depth, lat, lon) ;
>                  salt:long_name = "SALINITY" ;
>                  salt:units = "g/kg" ;
>                  salt:_FillValue = -9.99e+33f ;
>          float u(depth, lat, lon) ;
>                  u:long_name = "ZONAL VELOCITY" ;
>                  u:units = "m/sec" ;
>                  u:_FillValue = -9.99e+33f ;
>          float v(depth, lat, lon) ;
>                  v:long_name = "MERIDIONAL VELOCITY" ;
>                  v:units = "m/sec" ;
>                  v:_FillValue = -9.99e+33f ;
>          float w(depth, lat, lon) ;
>                  w:long_name = "VERTICAL VELOCITY" ;
>                  w:units = "m/sec" ;
>                  w:_FillValue = -9.99e+33f ;
>          float taulat, lon) ;
>                  taux:long_name = "TAUX" ;
>                  taux:units = "N/m^2" ;
>                  taux:_FillValue = -9.99e+33f ;
>          float tauy(lat, lon) ;
>                  tauy:long_name = "TAUY" ;
>                  tauy:units = "N/m^2" ;
>                  tauy:_FillValue = -9.99e+33f ;
>          float ssh(lat, lon) ;
>                  ssh:long_name = "SEA SURFACE HEIGHT" ;
>                  ssh:units = "m" ;
>                  ssh:_FillValue = -9.99e+33f ;
>          double lon(lon) ;
>                  lon:units = "degrees_east" ;
>          double lat(lat) ;
>                  lat:units = "degrees_north" ;
>          double depth(depth) ;
>                  depth:units = "meters" ;
>                  depthositive = "down" ;
>
> // global attributes:
>                  :title = "SODA 2.2.4, 1871-2008 Assimilation Run" ;
>                  :released = "July 20, 2010" ;
>                  ata_timestamp = "12-1873" ;
>
> The point to be noted here is that there is no time axis in these
> files (as it shows only lat,lon and depth). Because of this, merging
> these files using "cdo" command - "cdo -r
> mergetime" is found to be not working.
>
> Hence I am interested to know two things.
> 1) How to merge/append all these 120 files into a single file and that
> should also give the time axis as time = 120
> 2) After getting the appended file how to prepare monthly climatology
> using the appended file.
> 3) Is there any other way of preparing the monthly climatology of
> above 120 monthly files without going to the step of "creating an
> appended data file"?
>
> If anybody know a work around, please help me.
>
> Thanks in advance
>
> Sreejith.