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