Re: Right time with NCEP data?

From: Saji Njarackalazhikam Hameed <saji_at_nyahnyahspammersnyahnyah>
Date: Wed, 9 May 2007 12:05:42 +0900

Dear Louis,

As Mary pointed out correctly this is because NCL does not interpret the
time axis for you by itself. It is plotting whatever time coordinate is
available.

This is a problem that folks migrating from GrADs will have to deal on their
own. There was some discussion on the NCL mailing list on this issue, but
we did not find a suitable solution,I believe.

One way is to write some user-defined functions or procedures to
do the time-mapping (from given time-co-ordinates to a more recognizable
form).

I am including a suggestion of how one may do this. The following example
plots a simple time series. I have supplied the time axis in units of
"days since 1900-01-01". So the time axis goes from 38716 to 39204 in
increments of 1. This maps to time from 00Z01JAN2006 to 00Z04MAY2007.
I want to plot the time axis in a easy to read format. What I have done
is to define a procedure called time_axis_in_years. This will perform some
mappings and axis label settings and enable me to plot the time axis in
years. One can extend this to plot time axis in terms of years,months
and days, but the required coding will be large. I wish I could do this, but
right now I have no time.

See the attached files (example.ncl and time_axis_in_years.ncl). Please note
that the procedure time_axis_in_years.ncl has some "bugs"

1. The first year's label (for instance 2006) will be located at the
   beginning of the time series. This is undesireable if for instance
   the time series started in May 2006. With some extra coding, one can
   overcome this I believe.

2. there may be other deficiencies... anyway it will be nice if we
    can find a solution together (i think this is every body's problem).

cheers,

saji

* louis Vonder <appopson_at_yahoo.fr> [2007-05-05 14:00:39 +0200]:

> Dear ncl users,
> I am using NCEP/NCAR data, but when I am trying to plot hovmoller (lat, time) diagram of a variable I have time is very "big". something like 1754800.
>
> This make me wonder, because when using GRADS I have "normal time"
>
> There is a way to have right value of time using NCL?
>
> Thanks
>
>
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-- 
Saji N. Hameed
APEC Climate Center          				+82 51 668 7470
National Pension Corporation Busan Building 12F         
Yeonsan 2-dong, Yeonje-gu, BUSAN 611705			saji_at_apcc21.net
KOREA



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Received on Tue May 08 2007 - 21:05:42 MDT

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