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Fri Jun 13 09:45:15 BST 2003 | jobsheet

yacfa ([cp yabwb] For jiggering swapbounds, bh. ; 4.5)

  1. Start time: 2000/12/1, length: 10/0/3
  2. Processors: 1 * 2, Exec name: $RUNID.exe; Timestep (mins): 30 (atmos); 60 (ocean) . Coupling every (hours) 24
  3. Start dumps: $DUMPS/xahiya.da00c10 $DUMPS/xahiyo.da00c10
  4. Fortran mods
  5. Diags
  6. Userprestash files
  7. See-also: yabwb
  8. Notes:
    1. Notes go here...
  9. History: yacfa -> yabwb -> yabeo -> a -> yabad -> a -> yaauo -> n -> yaasc -> yaaoa

Purpose of Run (long)

Following (or rather, in series with) yacck is this run, which copies swpbnd1a.f from k, but nothing else. In particular it *doesn't* have "swapbounds logical" protection (because this version does anyway) and nor does it have the not-jiggering-in-relax (it does however have iteration print's in relax). It will be interesting to see what difference that makes.

swpbnd1a.f.

b is like a, but with 10^-14.

Note that although the code above *claims* to alternately jigger values by +/- 1e-9, in fact due to an error all values are jiggered by +. However this doesn't appear to be a problem.

Yacfc is similar to this except I used 1e-5,6,7 (which all die rapidly with fpe err) then e-8 which is OK.

Results

Well, interesting. Global T doesn't decline, as it does in yabwb at 32 bit. But there do appear to be problems, which on closer inspection are in yabwb too. Hmmm... does anyone else out there have anything on this?

Summary: global annual T is OK at 64 bit but not at 32 bit; when looking zonally there appear to be problems with 64 bit too towards the poles; the "degrading" above doesn't degrade the results.

Global T (all data annual means)

Appears to be OK:

Maps of T at year 15

Now its somewhat less clear that things are OK, since its quite hard to distinguish 32 and 64 bit versions.

Zonal Means (Diffs against first year of hadcm3 control)

Notice the "sine(lat)" x axis.

Notice: that hadcm3 diffs are always -ve in the tropics. Hadcm3 is known to be stable so this means that, most likely, the single year I've picked to diff against was a warm tropical year: this then biases all the results.

Notice: that the pattern of difference for the beowulf runs is quite characteristic (cooling in the polar-ish regions) and different from the inter-hadcm3 diffs. It isn't obvious from these pics that beowulf-32 is 0.8 oC globally cooler than beowulf-64 by year 15.

And now if we look at just yabwb (beowulf 64 bit) zonal means, in 15 year periods:

(thin lines: years; thick lines: 15 year averages; black: first 15; green; 16-30; red: 31-45 (actually to 43...)).

Past last modified: 4/8/2003   /   wmc@bas.ac.uk

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