date: Thu Apr 24 15:02:43 2008
from: Tim Osborn <t.osborn@uea.ac.uk>
subject: Re: Abnormal normals!
to: Ian Harris <i.harris@uea.ac.uk>

   Hi Harry,
   smoothing out the peaks might account for it, but (for pre) it seems too large a
   reduction.  Can you calculate the mean of each of the normals files, since presumably the
   mean should be unaltered by such smoothing.
   Cheers
   Tim
   At 12:09 24/04/2008, you wrote:

     Hi Tim,
     Sit down.. it's the 'scaling' business again!
     I've examined the rd0 and pre normals at half degree and two-half
     degree binary, and half-degree ascii (the clim files we publish).
     Here are the results and my interpretations:
     FILE                  MIN            MAX             UNITS
     glo25.rd0.6190          0            303           days*10
     glo25.pre.6190          0            391               ???
     glo.rd0.norm            0            310           days*10
     glo.pre.norm            0           1244                mm
     clim.6190.lan.wet.grid  0           3090          days*100
     clim.6190.lan.pre.grid  0          12430             mm*10
     As you can see, there is a big difference between the precip normals
     over all three versions! The best interpretation I can place on the
     2.5-deg binary normals ('???') is that the much larger area is
     'softening' the impact of individual high-recording stations.. what
     do you think?
     We can see from the rd0_gts_tdm.pro program that they are treated as
     days*10 (rd0) and mm (pre), assuming natural units are in play:
     rd0norm(nland)=(rd0norm(nland)/10)>0.49
     prenorm(nland)=prenorm(nland)>5.0
     I wonder if the squashing of variability in the 2.5 degree grid is
     causing the low variability you're seeing in the output?
     I will try running with half-degree synthetics to give us a comparison.
     Cheers
     Harry
     Ian "Harry" Harris
     Climatic Research Unit
     School of Environmental Sciences
     University of East Anglia
     Norwich NR4 7TJ
     United Kingdom
