[NARCCAP-discuss] time discrepancy
Seth McGinnis
mcginnis at ucar.edu
Sun Aug 26 10:10:45 MDT 2012
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
>>
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