Monday, June 18, 2012

5307.txt

cc: Tim Osborn <t.osbornatXYZxyz.ac.uk>
date: Thu, 24 Apr 2008 10:41:18 +0100
from: Ian Harris <i.harrisatXYZxyz.ac.uk>
subject: Re: CRU TS 3.0
to: Gerard van der Schrier <schrieratXYZxyzi.nl>

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Hi Gerard,

On 24 Apr 2008, at 08:49, Gerard van der Schrier wrote:
> Hi Tim & Harry,
>
> Would you happen to have information at which gridpoints the CRU TS
> 3.0 data are relaxed to climatology?

Ahhh. Great question! We do have 'station files' - these give the
number of stations theoretically contributing to each cell. Where
it's a zero, and it's also a land cell, you'll get (full) relaxation
to the climatology. However, that won't show you 'strong relaxation',
I'm not sure if your current approach isn't the most pragmatic!

However, I'm happy to make the relevant station files available to you:

http://www.cru.uea.ac.uk/~harry/for_gerard/

Counts of stations actually IN each cell:
cru_ts_3_00.1901.2006.tmp.cstn.dat.gz

Counts of stations theoretically contributing to each cell:
cru_ts_3_00.1901.2006.tmp.stn.dat.gz

NetCDF versions of the above:
cru_ts_3_00.1901.2006.tmp.cstn.nc.gz
cru_ts_3_00.1901.2006.tmp.stn.nc.gz

Cheers

Harry


>
> I'm working on the PDSI now, and the self-calibrating aspect of the
> algorithm does not really like climatology. When a gridbox is
> strongly relaxed towards climatology, only a very minor deviation
> from climatology makes the algorithm think that a major dourght or
> pluvial is happening!
>
> I've "solved" these problems by calculating standard deviation for
> each gridbox, and then specifying that if the standard deviation is
> below some threshold, then I skip calculating the PDSI.
>
> I guess that the gridboxes which are relaxed strongest to
> climatology are also in the areas where the PDSI does not make
> sense anyway, like deserts or tundra......
>
> Cheers, Gerard
>
> --
> ----------------------------------------------------------
> Gerard van der Schrier
> Royal Netherlands Meteorological Institute (KNMI)
> dept. KS/KA
> PO Box 201
> 3730 AE De Bilt
> The Netherlands
> schrieratXYZxyzi.nl
> +31-30-2206597
> www.knmi.nl/~schrier
> ----------------------------------------------------------
>

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


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