Re: Add DATE in an exsisting NC file

Simone,

It is unclear what you are asking. If you want to write a single date into a Netcdf file, then I suggest writing a global string attribute named "date" with a value of, for example, "2007-May-17" or "2007-05-17". (First form preferred to prevent ambiguity. Always use four digit years.)

If your file contains a time series, and you want to add a list of dates to identify the time steps, then I strongly recommend that you add a numeric time coordinate variable that uses Udunits time encoding, and follows certain Netcdf standard conventions:

http://www.unidata.ucar.edu/software/udunits/
http://www.unidata.ucar.edu/software/netcdf/conventions.html

I use parts of the COARDS and CF conventions for time coordinates, with good compatibility for graphics software such as Grads and NCL.

For a brief introduction, see the paragraphs on coordinate systems and calendar in the Best Practices document:

http://www.unidata.ucar.edu/software/netcdf/docs/BestPractices.html

Here are my minimum recommendations to make a simple time coordinate variable:

Add a time coordinate array that is type double and one dimensional. DO NOT use a string array.

Name of time dimension = time
Name of time coordinate variable = time

Minimum attributes:
* units = "days since 1800-1-1 0:0:0"
* calendar = "gregorian"
* long_name = "Time"

It is good to also include the optional actual_range attribute, a type double array of dimension (2), containing the first and last values from the time coordinate variable.

This is a basic prototype for you. There are complexities regarding the data type and attributes that I will not go into unless needed. I hope this gets you started.

--Dave A.
CU/CIRES Climate Diagnostics Center (CDC)
NOAA/ESRL/PSD, Climate Analysis Branch (CAB)

Simone Marras wrote:
Good morning, I am dealing with a set of *.nc files which do not contain any date nor information on the time and, for what I need to do with those files, I actually need to add the DATE as YY-MM-DD in the files.

Has anyone ever gone through this?
I hope someone can help me with this

Thank you in advance,

Regards

Simone

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