Re: Add DATE in an exsisting NC file


I forgot to mention something. The name of your new time coordinate array must be the same as the time dimension of your data.

For example, if the existing data in your Netcdf file has named dimensions var(lon,lat,time), then the time coordinate variable must be time(time). For var(x,y,t) you would add t(t). I like "time" as the dimension name, but another appropriate name like "t" is okay, since your data may already have a named dimension for time.

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

Simone Marras wrote:
Hello Dave, thank you very much for the helping reply. It is quite clear and I will follow your instructions. I am new in netcdf but it seems quite straight forward to program

All the best


On Thursday 17 May 2007 23:13, Dave Allured wrote:

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:

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:

Here are my minimum recommendations to make a simple time coordinate

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,


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