Monday, March 5, 2012


cc: Phil Jones <>
date: Wed, 7 May 2008 13:27:18 +0100
from: Ian Harris <>
subject: Re: wetdays... yippee!
to: Tim Osborn <>

Hi Tim,

On 7 May 2008, at 13:03, Tim Osborn wrote:
> Hi Harry and Phil,
> Not a cry for some rain... instead relief that we now appear to
> have a usable wetday file. :-)
> The patterns of means, standard deviations and correlations with
> CRU TS 2.1 data all look reasonable (obviously with a slightly
> lower correlation over some, e.g. Russian, regions because 2.1 has
> the step-change in wetdays due to the data inhomogeneity).
> The country-mean, seasonal time series are attached. The step in
> 2.1 (the red lines) is clearly avoided in the new 3.0 (the black
> lines).
> The version I've used is the usual CRU TS approach from 1901-1989
> -- i.e., the results of gridding the station wetday data together
> with the 2.5-degree grid of synthetic wet day -- and then switching
> to completely synthetic wet days calculated directly on the 0.5-
> degree grid from the 0.5-degree pre, for 1990-2005 (I've ignored
> 2006, but the same should be done for that and beyond, until the
> post-1989 station wetday data is sorted out at some future time).
> Assuming you're both happy with the attached country-mean time
> series, then can we settle on this as *the* CRU TS 3.0 wetday data
> set?

I expect that's pragmatic; but I'm not sure Canada looks right, and
the dry African states/countries have a different unrealistic pattern
to 2.1..

> In which case, I can give it to our QUEST partners, and Harry can
> you make up a new 1901-2006 pair of files containing this final
> combination? Currently I'm reading the separate files and
> combining them as described above, but a single file would be
> easier for me (and others) to deal with.


> Well done for your work on all these multiple iterations/approaches
> Harry.
> Assuming you're happy with wetdays, then that means all CRU TS 3.0
> is done except CLD and FRS (the latter is made but I've not checked
> it, so its not impossible that there's some factor-of-10 error).

Agreed entirely.

> Harry -- FYI Allan Spessa has asked overall QUEST (i.e. not our
> particular QUEST project) if they'll pay a month's salary to us to
> help us get CLD working. As you noted before, it is not just down
> to money, but rather to time, given the demands of our QUEST
> project for future scenarios now. If QUEST do find the money,
> therefore, then I'll ask Douglas to do the work on recreating the
> coefficients that Mark New/Tim Mitchell couldn't find for making
> synthetic CLD. That seems an easily separable task from the actual
> gridding stage. Once synthetic CLD is made, you would then of
> course be involved in the gridding stage -- though if you were
> documenting the CRU TS process, it might prove to be a useful trial
> run for Douglas to attempt to follow your instructions and see if
> they can get him through the process? One thing I'm not sure about
> is the status of the station data base for CLD... assuming we're
> not basing the updates (post-2002) entirely on synthetic data, then
> presumably station CLD (estimated mostly -- or entirely? -- from
> station sunshine) updates are needed. Are these done already? If
> not, do you have code ready to do this sunshine-->cloud
> conversion? Am I barking up the wrong tree?

It's very complicated, there's a whole raft of related programs I'm
afraid, and dozens of data files. I can't remember what stage I got
to but I do have notes. And Douglas is an excellent choice ;-)

> Sorry for the long email... nearly there!
> Thanks for all your hard work on this Harry. I'd like to be able
> to let you take a bit of a break and catch up with non-project
> things. Unfortunately, after 6 weeks hard work from both of us,
> we've now reached the stage that I already thought we'd reached at
> Easter, when I was panicking about how far behind we were! :-(

I did guess. I was going to ask for a week to sort out a non-IDL
gridding package ;-)

> So... when you've made the final wet files, please can you get back
> to the climate change pattern diagnosis from the GCM runs. You'll
> probably need to get up to speed with where you'd got to. I have
> patterns for 'tas' (i.e., near-surface mean temperature) and
> 'pre' (including relative and exponential ones) from you. For
> those GCMs with min and max temp data, could you follow the same
> procedure as for 'tas', to make patterns for tmin, tmax and also
> repeat it using tmax-tmin to get patterns for dtr.

Understood. Will spin up the disks and re-read the project diary!

> Then I'll give you some guidance for diagnosing precip variability,
> cloud and vapour pressure patterns as they differ a bit from the
> other variables.

OK. I will still have to fiddle with the automation of the TS process
though; I'll do that in non-work time. As you'll have seen, BADC are
getting edgy, and high-level interrupt routines may be kicking in


Ian "Harry" Harris
Climatic Research Unit
School of Environmental Sciences
University of East Anglia
Norwich NR4 7TJ
United Kingdom


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