cc: Phil Jones date: Thu, 18 Oct 2007 12:19:26 +0100 from: Ian Harris subject: Re: CRU TS Secondaries Strategy to: Tim Osborn Hi Tim, As I understand it, the strategy is to move towards all regularly- reported parameters being 'Primaries', so I don't have the luxury of lifting the carpet. I agree that the secondary databases are in varying states of repair - but to be frank so are the rest. I have seen a few horrors in the 'wet' database - but I've seen them in more, er, important databases too. I'm currently working with rd0/wet and there's plenty of modern data. The solution I'm using is actually an option in the IDL gridding prog (quick_interp_tdm2.pro) that allows both synthetic and observed data to be used - with synthetic supplanting the observations. This will allow observations to take over as the relevant database is improved. Cheers Harry On 18 Oct 2007, at 12:06, Tim Osborn wrote: > I was about to reply to say that I didn't think you had time to do > the proposed solution, because by starting to use direct > observations of the secondary parameters that have not previously > been used, you may well uncover a multitude of data quality and > homogeneity problems and difficulties in identifying stations etc. > that would not arise if you ignored the secondary observations and > stuck with derivations from the primary obs that have already been > used. Your solution might have been better, but unfortunately no > time available to try it. > > However now you have an alternative solution... hopefully not > involving more time or the risk of using previously unused obs? > > Cheers > > Tim > > At 11:56 18/10/2007, Ian Harris wrote: >> Hi, >> >> Scratch all that - I've found a neater solution. >> >> Cheers >> >> Harry >> >> On 17 Oct 2007, at 14:03, Ian Harris wrote: >> >>> Hi, >>> >>> I've been mulling over a strategy issue. >>> >>> CRU TS Secondary parameters are currently derived from: >>> >>> 1. One or more Primary parameters, gridded (to 2.5°, for some >>> reason) >>> 2. Normals for the Primary parameter(s) >>> 3. Normals for the Secondary parameter >>> >>> The IDL routines do not allow for genuine observations of the >>> secondary parameter to be incorporated. >>> >>> The problem is that we should be moving towards using secondary >>> observations where available. If we just pick a changeover point, >>> there are likely to be noticeable discontinuities - also we >>> probably don't have enough observations to do that yet! >>> >>> So, what I propose is this: >>> >>> 1. Produce Secondaries as Secondaries (using synthetically- >>> generated data from Primaries) >>> 2. Produce Secondaries as if they were Primaries (ie using direct >>> observations of Secondary values) >>> 3. Let the output from 2 overwrite the output from 1 WHERE the >>> actual station count is >=1. >>> >>> In other words, the synthetic data is replaced with 'genuine' data >>> if there is at least one station reporting within the cell at that >>> timestep. >>> >>> How does that sound? Any better ideas? It has the advantage that it >>> doesn't require a great deal of coding ;-) >>> >>> Harry >>> Ian "Harry" Harris >>> Climatic Research Unit >>> School of Environmental Sciences >>> University of East Anglia >>> Norwich NR4 7TJ >>> United Kingdom >>> >> >> Ian "Harry" Harris >> Climatic Research Unit >> School of Environmental Sciences >> University of East Anglia >> Norwich NR4 7TJ >> United Kingdom >> > > Dr Timothy J Osborn, Academic Fellow > Climatic Research Unit > School of Environmental Sciences > University of East Anglia > Norwich NR4 7TJ, UK > > e-mail: t.osborn@uea.ac.uk > phone: +44 1603 592089 > fax: +44 1603 507784 > web: http://www.cru.uea.ac.uk/~timo/ > sunclock: http://www.cru.uea.ac.uk/~timo/sunclock.htm > > Ian "Harry" Harris Climatic Research Unit School of Environmental Sciences University of East Anglia Norwich NR4 7TJ United Kingdom