cc: Tim Osborn date: Thu, 24 Apr 2008 10:41:18 +0100 from: Ian Harris subject: Re: CRU TS 3.0 to: Gerard van der Schrier 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 > schrier@knmi.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