[ncl-talk] time_to_newtime vs. cd_convert

Tue Oct 7 04:58:59 MDT 2014

Related question... What's the difference between cd_convert and
time_to_newtime?

Looking at the code, I think they just handle the metadata a little
differently. Notably, time_to_newtime updates the coordinate variable
(something I forgot to do when I originally wrote ut_convert).

Perhaps they should be reconciled into one function and the other one
marked as deprecated or as an alias on the website?

    Carl

On Mon, Oct 6, 2014 at 10:55 PM, Lam Hoang <lamhpvn at gmail.com> wrote:

> Hi Alan,
> I'm using NCL 6.1.2 and your code works perfectly.
>
> Variable: t
> Type: double
> Total Size: 20440 bytes
>             2555 values
> Number of Dimensions: 1
> Dimensions and sizes:    [time | 2555]
> Coordinates:
>             time: [ 0.5..2554.5]
> Number Of Attributes: 6
>   bounds :    time_bnds
>   units :    days since 2006-01-01 00:00:00
>   calendar :    noleap
>   axis :    T
>   long_name :    time
>   standard_name :    time
>
> Variable: t
> Type: double
> Total Size: 20440 bytes
>             2555 values
> Number of Dimensions: 1
> Dimensions and sizes:    [time | 2555]
> Coordinates:
>             time: [56940.5..59494.5]
> Number Of Attributes: 6
>   calendar :    noleap
>   units :    days since 1850-01-01 00:00:00
>   bounds :    time_bnds
>   axis :    T
>   long_name :    time
>   standard_name :    time
>
> Best regards,
> Lam
>
> On Tue, Oct 7, 2014 at 5:07 AM, Alan Brammer <abrammer at albany.edu> wrote:
>
>> What version of ncl are you using? I just tested a similar few lines of
>> code in 6.1.1 and 6.2.0 and they both copied the calendar attribute as
>> expected. Also have you tried cd_convert() seems to do the same thing?
>>
>> However in these tests and looking around I have a strong suspicion there
>> is a significant bug in this function.  In that the code copies the
>> calendar attribute but does not actually make use of it and thus returns
>> the wrong answer disguised as the correct one.
>>
>>
>> Attached is my edited code.  load this below a load "....contibuted.ncl"
>> line if you have one and this version of the code will replace the stock
>> version.  A developer will hopefully weigh in with more insight in this.
>>
>>
>> Good luck,
>>
>> Alan
>>
>>
>>
>>
>>
>> On Fri, Oct 3, 2014 at 10:08 PM, Lam Hoang <lamhpvn at gmail.com> wrote:
>>
>>> Dear NCL supporting team,
>>> I want to convert the time units from a CMIP5 model to make them unique.
>>> I try to use time_to_newtime function but unfortunately after convert
>>> the time units, the calendar attribute changes to "gregorian" as well.
>>> What should I do if I want to keep the calendar attribute as the
>>> original time variable?
>>>
>>> Regards,
>>> Lam
>>>
>>>
>>> f =
>>> addfile("./oldtime_psl_day_NorESM1-M_historicalExt_r3i1p1_20060101-20121231.nc","r")
>>> temp = f->psl
>>> t = f->time
>>>
>>> printVarSummary(t)
>>>
>>> *** Variable: t
>>>
>>> *** Type: double
>>>
>>> *** Total Size: 20440 bytes
>>>
>>> ***             2555 values
>>>
>>> *** Number of Dimensions: 1
>>>
>>> *** Dimensions and sizes: [time | 2555]
>>>
>>> *** Coordinates:
>>>
>>> ***             time: [ 0.5..2554.5]
>>>
>>> *** Number Of Attributes: 6
>>>
>>> ***   bounds : time_bnds
>>>
>>> ***   units : days since 2006-01-01 00:00:00
>>>
>>> ***   calendar : noleap
>>>
>>> ***   axis : T
>>>
>>> ***   long_name : time
>>>
>>> ***   standard_name : time
>>>
>>> t = time_to_newtime(t, "days since 1850-01-01 00:00:00")
>>>
>>> printVarSummary(t)
>>>
>>> *** Variable: t
>>>
>>> *** Type: double
>>>
>>> *** Total Size: 20440 bytes
>>>
>>> ***             2555 values
>>>
>>> *** Number of Dimensions: 1
>>>
>>> *** Dimensions and sizes: [time | 2555]
>>>
>>> *** Coordinates:
>>>
>>> ***             time: [56978.5..59534.5]
>>>
>>> *** Number Of Attributes: 6
>>>
>>> ***   calendar : gregorian
>>>
>>> ***   units : days since 1850-01-01 00:00:00
>>>
>>> ***   bounds : time_bnds
>>>
>>> ***   axis : T
>>>
>>> ***   long_name : time
>>>
>>> ***   standard_name : time
>>>
>>>
>>> --
>>> Hoang Phuc Lam
>>> Viet Nam National Center of Hydro-Meteorology Forecasting
>>> National Hydro-Meteorological Services of Vietnam
>>> Mob: +84 12 1616 5258
>>> Tel:   +844 38247002
>>> Fax:  +844 38254278
>>>
>>> _______________________________________________
>>> ncl-talk mailing list
>>> List instructions, subscriber options, unsubscribe:
>>> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>>>
>>>
>>
>
>
> --
> Hoang Phuc Lam
> Viet Nam National Center of Hydro-Meteorology Forecasting
> National Hydro-Meteorological Services of Vietnam
> Mob: +84 12 1616 5258
> Tel:   +844 38247002
> Fax:  +844 38254278
>
> _______________________________________________
> ncl-talk mailing list
> List instructions, subscriber options, unsubscribe:
> http://mailman.ucar.edu/mailman/listinfo/ncl-talk
>
>

-- 

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<http://www.researcherid.com/rid/B-8711-2011>
* Cyclone <http://www.cyclonecenter.org/>*Center.org
<http://www.cyclonecenter.org/>  *Carl J. Schreck III, PhD*
*Research Associate*
Cooperative Institute for Climate and Satellites NC <http://www.cicsnc.org/>

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