[NARCCAP-discuss] time discrepancy

Sat Sep 8 16:05:28 MDT 2012

Hi Seth,

Thanks for letting me know. The missing numbers are showing in the
pulled time variable, before I do any date calculations in Excel. My
program is taking all .nc files for a particular variable and
generating a single daily statistics CSV, so it is likely that my
program has a bug, especially considering that the missing dates tend
to fall on the end of the year (and so the end of a file).

Thanks for all your help...

Shane

On Fri, Sep 7, 2012 at 1:34 PM, Seth McGinnis <mcginnis at ucar.edu> wrote:
> Hi Shane,
>
> The values in the time coordinate variable should be continuous in all the
> published data, with only a couple exceptions (noted on the Data Status page).
>
> This sounds like a problem related to Excel's representation of dates.  Are the
> skips all after leap years?  One way to check that hypothesis would be to
> download some of the data driven with HadCM3, which uses a 360-day calendar.
>  If that is the problem, then you'll probably get jumps of 5 or 6 days at the
> end of each year.  (Note that there's a repeated timestep between the first and
> second files in the HRM3-hadcm3 driven runs; this problem is very nearly fixed,
> and I expect to publish corrected data next week.)
>
> The other possibility that springs to mind is that maybe your file downloads
> were truncated, and you lost the last few steps on some files.  In that case,
> try downloading one of the problem files again.
>
> Cheers,
>
> --Seth
>
> On Thu, 6 Sep 2012 12:04:42 -0400
>  Shane Brennan <sbren006 at odu.edu> wrote:
>>Hi Seth,
>>
>>I notice "time" data skips a day near the end of the year in some
>>cases. For example, in a few files I have looked at, the "time"
>>variable goes from 1093 to 1095, as well as 2918 to 2920, etc. This
>>does not happen in NCEP files which are Gregorian. Is this a
>>consequence of the no leap year calendar? I had assumed that "time"
>>counted up from 0 (from 1968) and that day 59 would be a leap day in
>>Gregorian and March 1st in the no leap year calendar.
>>
>>Basically, I would like to compare NCEP data with modeled data on a
>>monthly basis, so making sure I have my calendars straight is
>>important. Does anyone have any suggestions on the best way to go
>>about this? Currently I am creating two "days from" fields in Excel
>>which have the time variable, and in one field I increment the value
>>(and subsequent values) at leap years, all the way down, so that the
>>final product is a field with the correct days offset depending on the
>>number of preceding leap days. However, the skipped day I am running
>>in to is causing me to put this method into question.
>>
>>Thanks, and sorry if I am missing something obvious...
>>
>>Shane
>>
>>
>>On Sun, Aug 26, 2012 at 12:10 PM, Seth McGinnis <mcginnis at ucar.edu> wrote:
>>> Hi Shane,
>>>
>>> Information about time in the NARCCAP data can be found here:
>>> http://narccap.ucar.edu/about/time-periods.html
>>>
>>> Cheers,
>>>
>>> --Seth
>>>
>>> On Sat, 25 Aug 2012 16:09:54 -0400
>>>  Shane Brennan <sbren006 at odu.edu> wrote:
>>>>OK, thanks, Seth. Is the same calendar used for all models? Is there
>>>>documentation on the timesteps used?
>>>>
>>>>Shane
>>>>
>>>>On Sat, Aug 25, 2012 at 11:25 AM, Seth McGinnis <mcginnis at ucar.edu> wrote:
>>>>> Hi Shane,
>>>>>
>>>>> It's the calendar.  CCSM uses a 365-day or "noleap" calendar, in which
>>every
>>>>> year has 365 days and there are no leap years ever.  The date calculation
>>>>> functions in Excel use the standard Gregorian calendar, which does have
>>leap
>>>>> years.
>>>>>
>>>>> If you count up the leap days between the base time (1968/01/01) and the
>>>>start
>>>>> of your file (1996/01/01), there are seven of them, which is the
>>difference
>>>>> between your expected start date and the start date you're seeing in the
>>>>Excel
>>>>> calculations.  (And then there's another one in 1996, so the discrepancy
>>for
>>>>> the end dates is 8 days.)
>>>>>
>>>>> Cheers,
>>>>>
>>>>> --Seth
>>>>>
>>>>> On Fri, 24 Aug 2012 11:13:44 -0400
>>>>>  Shane Brennan <sbren006 at odu.edu> wrote:
>>>>>>Hi,
>>>>>>
>>>>>>I am writing a C# program to parse and manipulate NARCCAP data. I
>>>>>>wanted to verify the missing data values to make sure I was handling
>>>>>>them correctly so I checked out:
>>>>>>
>>>>>>http://www.narccap.ucar.edu/data/missing/CRCM_ccsm-current_table3_missing.txt
>>>>>>
>>>>>>to find where I could look for missing values. In the URL above, it
>>>>>>states that evps in the file evps_CRCM_ccsm_1996010103.nc has missing
>>>>>>values for 1999-12-01 03:00 through 2000-01-01 00:00.
>>>>>>
>>>>>>I would expect the time series for the entire file to run from
>>>>>>1996-01-01 03:00 to 2000-01-01 00:00. However, when I parse this file
>>>>>>with my program and then use excel to calculate the times from
>>>>>>1/1/1968 (the start date returned from ncdump for this file), I get a
>>>>>>time series that runs from 12/25/1995 03:00 to 12/24/1999 00:00. In
>>>>>>this file, my missing values run from 11/23/1999 03:00 to 12/24/1999
>>>>>>00:00.
>>>>>>
>>>>>>Naturally, I became concerned that I had a bug in my program. However,
>>>>>>when I use nc2text.exe using the instructions detailed in the ASCII
>>>>>>HowTo, I get the same results.
>>>>>>
>>>>>>In Excel I calculate the offset date by entering 1/1/1968 into a cell,
>>>>>>and calculating a new field as that cell value added to each time
>>>>>>value (for example, if the cell for 1/1/1968 is G1, then my formula
>>>>>>for the first cell is "=$G$1 + a1". I then copy this formula all the
>>>>>>way down).
>>>>>>
>>>>>>Does anyone know what is going on? Perhaps there is some issue with
>>>>>>leap years or DST?
>>>>>>
>>>>>>Shane
>>>>>>_______________________________________________
>>>>>>narccap-discuss mailing list
>>>>>>narccap-discuss at mailman.ucar.edu
>>>>>>http://mailman.ucar.edu/mailman/listinfo/narccap-discuss
>>>>>
>>>>> _______________________________________________
>>>>> narccap-discuss mailing list
>>>>> narccap-discuss at mailman.ucar.edu
>>>>> http://mailman.ucar.edu/mailman/listinfo/narccap-discuss
>>>>>
>>>>>
>>>>> --
>>>>>
>>>>_______________________________________________
>>>>narccap-discuss mailing list
>>>>narccap-discuss at mailman.ucar.edu
>>>>http://mailman.ucar.edu/mailman/listinfo/narccap-discuss
>>>
>>> _______________________________________________
>>> narccap-discuss mailing list
>>> narccap-discuss at mailman.ucar.edu
>>> http://mailman.ucar.edu/mailman/listinfo/narccap-discuss
>>>
>>>
>>> --
>>>
>>_______________________________________________
>>narccap-discuss mailing list
>>narccap-discuss at mailman.ucar.edu
>>http://mailman.ucar.edu/mailman/listinfo/narccap-discuss
>
> _______________________________________________
> narccap-discuss mailing list
> narccap-discuss at mailman.ucar.edu
> http://mailman.ucar.edu/mailman/listinfo/narccap-discuss
>
>
> --
> BEGIN-ANTISPAM-VOTING-LINKS
> ------------------------------------------------------
>
> Teach CanIt if this mail (ID 700236910) is spam:
> Spam:        https://www.spamtrap.odu.edu/b.php?i=700236910&m=0ab5679d625f&t=20120907&c=s
> Not spam:    https://www.spamtrap.odu.edu/b.php?i=700236910&m=0ab5679d625f&t=20120907&c=n
> Forget vote: https://www.spamtrap.odu.edu/b.php?i=700236910&m=0ab5679d625f&t=20120907&c=f
> ------------------------------------------------------
> END-ANTISPAM-VOTING-LINKS
>