Apologies in advance if this is the wrong forum, but it seems appropriate here. Also apologies for longish post.
Corrections for timecodes in cryosphere dataI have been using the cryosphere data (
http://arctic.atmos.uiuc.edu/cryosphere/timeseries.anom.1979-2008) for a
couple of years for fun and no profit (as well as IJIS, PIOMAS and NSIDC).
At the time I set up an automated import into a database (PostgreSQL), and noted that the timecodes were not unique. I did not bother to look further then but just turned of the indexing on the timecode.
I have recently had some time on my hands and decided to have a closer look and after a few hours work found several inconsistencies and probable typos.
There are 366 data points for all years divisible by 4 and 365 for all others (except 1979 only had 364 values, 1979.0000 is missing). Note that 2000 is therefore considered a leap year. I use the term Y4 instead of leap year as a reminder that it is not strictly leap years.
Focusing first on the non-Y4 years I found the following inconsistencies (timecodes that are not
round(d*365/10000) where d is the day of the year), some which appear to be obvious typos:
- 1987.9253 -> 1987.9233
- 2005.1088 -> 2005.1096
- 2005.8650 -> 2005.8658
- 2010.0928 -> 2010.0932
- 2009.4274 -> 2009.4247 (duplicate code, only correct the first occurrence)
In addition, the block of values 2007.9315 - 2007.9808 (19 values) have been shifted 1 step (~0.0027) since the code 2007.9288 is missing and 2007.9808 is a duplicate.
The following will fix this:
- for codes 2007.9342 - 2007.9780, set the code to the code on the previous line
- change 2007.9315 -> 2007.9288 (missing time code)
- change 2007.9808 -> 2007.9780 (first occurrence, duplicate entry).
This will make all non-Y4 years compact (365 values) and monotonically increasing by 1 day (~0.00274).
For the Y4 years there is more to do, I believe that approximately 3/4 of the year is one day off but this requires some more explanation.
I will post details on the Y4 years (which fixes all values with one glaring exception) if there is interest, either here or if I am pointed to some other appropriate forum.
Update: I have created a separate thread for this:
http://forum.arctic-sea-ice.net/index.php/topic,1251.0.html