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Re: [ferret_users] Descriptive file



Hi Steeven,
The time axis in your yearly files doesn't have what  Ferret needs in order to recognize the year.  Probably make_des has the same trouble.  The attribute
        time:comment = "Year 1958" ;

isn't standard, and so the software can't make use of it.  I think that if you add  the time origin to the units attribute then this will work.

The CF conventions describe the attributes for a time axis, http://cf-pcmdi.llnl.gov/

and the time-axis information is here.
http://cf-pcmdi.llnl.gov/documents/cf-conventions/1.5/ch04s04.html

The time origin must be defined relative to the coordinate values in the file. If the months are 1, 2, 3, ..., 12 then for 1958, the time origin would be the last month in 1957. So you will use something like 15-Dec-1957, or 1-Dec-1957 if you want to treat the months as if they are centered at the start of the month.



On 12/28/2010 3:56 AM, Steeven Paul Yerraguntla wrote:
Dear ferreters,
        I have 50 nc files, each file consists of 12 months  (l=1:12).  I wanted to merge them to one cdf file or des file so that i can have l=1:600. when i used make_des, i am getting des file with only first file 12 month values(l=1:12) and interstingly showing no error message while running " perl make_des file1.cdf file2.cdf  > test.des " or using output des file.   
        I used to define time axis and with help of time stamp i could append the files to a dummy file.cdf, if those files have single month. As each file having 12 time points, i do not know how to define time axis or merge all files in ferret.

ncdump of one of my files as follows.
netcdf evapr_oaflux_1958 {
dimensions:
    time = UNLIMITED ; // (12 currently)
    lat = 180 ;
    lon = 360 ;
variables:
    float lon(lon) ;
        lon:long_name = "longitude" ;
        lon:units = "degrees" ;
        lon:range = "0.5 to 359.5" ;
    float lat(lat) ;
        lat:long_name = "latitude" ;
        lat:units = "degrees" ;
        lat:range = "89.5S to 89.5N" ;
    int time(time) ;
        time:units = "month" ;
        time:comment = "Year 1958" ;
    short evapr(time, lat, lon) ;
        evapr:comments = "monthly mean evaporation rate" ;
        evapr:units = "cm/yr" ;
        evapr:scale_factor = 0.1 ;
        evapr:missing_value = 32766. ;
    short err(time, lat, lon) ;
        err:comments = "monthly mean estimated error of evaporation rate" ;
        err:units = "cm/yr" ;
        err:scale_factor = 0.1 ;
        err:missing_value = 32766. ;

// global attributes:
        :creation_date = "Dec 2007" ;
        :description = "WHOI Objectively Analyzed air-sea Fluxes (OAFlux) Project" ;
        :project_PIs = "Lisan Yu, Bob Weller" ;
        :website = "http://oaflux.whoi.edu" ;
data:

 lon = 0.5, 1.5, 2.5, 3.5, 4.5, 5.5, 6.5, 7.5, 8.5, 9.5, 10.5, 11.5, 12.5,
    13.5, 14.5, 15.5, 16.5, 17.5, 18.5, 19.5, 20.5, 21.5, 22.5, 23.5, 24.5,
    ...................................................................................................
    348.5, 349.5, 350.5, 351.5, 352.5, 353.5, 354.5, 355.5, 356.5, 357.5,
    358.5, 359.5 ;

 lat = -89.5, -88.5, -87.5, -86.5, -85.5, -84.5, -83.5, -82.5, -81.5, -80.5,
    ----------------------------------------------------------------------------------------------------------
    75.5, 76.5, 77.5, 78.5, 79.5, 80.5, 81.5, 82.5, 83.5, 84.5, 85.5, 86.5,
    87.5, 88.5, 89.5 ;

 time = 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 ;
}

 I searched archives but could not find suitable thread for my problem. Please let me know how to make it out either with make_des or nc2mc or within ferret itself.

Thanks n regards,
- paul.
--
Steeven Paul Y
Research Fellow
National Institute of Oceanography(NIO)
Regional Center Visakhapatnam (RCW)
176 Lawsons Bay Colony
Visakhapatnam - 530001






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