Aggregating Pentad Data Files

[Jennifer M. Adams]

Scott,
I don't like your 'trick' (saying it's daily data when it's really
pentad) because it leads to dreadfully inaccurate time metadata. No
wonder your monthly averages don't match up -- how is GrADS suppsed
to know what to average? A better strategy would be to rename your
files (or set up symbolic links) that have the actual date of each
pentad. Something like:
      pentad.19790101.data
      pentad.19790106.data
      pentad 19790111.data
Then, you have a DSET and TDEF like this:
DSET ^pentad.1979%m2%d2.data
TDEF linear 01jan1979 5dy

Jennifer


On Jun 13, 2006, at 12:56 AM, Scott Weaver wrote:

> Hi Everyone,
>
> I have what seems to be a strange problem.  I have calculated 36
> Pentad
> (5 day averaged) data files originally from 3hour time blocks (40 data
> files per pentad).  These files are named:
>
> 1979.pentad.1.data
> 1979.pentad.2.data ...
> ...
> 1979.pentad.36.data
>
> When displaying and verifying these files against monthly averages
> from
> the same dataset (someone else calculated) everything checks out
> for the
> first 30 pentads (5 months).  (i.e when I average all of the pentads
> separately for Jan - May it matches each monthly average nearly
> perfectly)
> When I check the pentads for June, #'s 31-36, it's way off from the
> independent monthly average for June.  I suspect the error is in my
> ctl
> file that I use to display the final pentads.  In the tdef I say it is
> daily data even though it is pentad.  I even tried using 5dy but the
> problem still exists.  See ctl file below.  I would be very
> grateful for
> any suggestions.
>
> THANK YOU,
> Scott
> *******************************************
> dset ^1979.pentad.%d1.data
> options template
> undef 9.999E+20
> title testing_pentad.ctl
> xdef 301 linear -180 0.5
> ydef 151 linear 10 0.5
> tdef 36  linear 00z01jan1979 1dy  ** really means pentad
> zdef 29 levels
> 1000 975 950 925 900 875 850 825 800 775 750 725 700 650 600 550
> 500 450
> 400 350 300 275 250 225 200 175 150 125 100
> vars 2
> APCPsfc  0 61,1, 0  ** surface Total precipitation [kg/m^2]
> prmslmsl 0 2,102,0 ** mean sea level pressure
> ENDVARS
>
>
>
>
>
>
> ______________________________________________
> Scott J. Weaver
> PhD Candidate
> Graduate Research Assistant
> Department of Atmospheric and Oceanic Science
> University of Maryland
> College Park, MD 20742
> 301-785-7201
> sweaver at atmos.umd.edu
>

Jennifer M. Adams
IGES/COLA
4041 Powder Mill Road, Suite 302
Beltsville, MD 20705
jma at cola.iges.org