cc: Phil Jones date: Mon, 14 May 2007 17:25:44 +0100 from: Ian Harris subject: Re: cru ts2.1 to: Sandy.Harrison@bristol.ac.uk Hi Sandy, Please see: New, M., M. Hulme and P. Jones (1999). "Representing twentieth- century space-time climate variability. Part I: Development of a 1961-90 mean monthly terrestrial climatology." Journal of Climate 12: 829-856. It's available as a PDF here: http://www.ouce.ox.ac.uk/~mnew/research/publications/ new_et_al_20th_climate_part1_JoC.pdf On page 832 they discuss the definition of a 'wet day' - the decision is to go with 0.1 mm. However, do bear in mind that the CRU TS 2.1 'rd0' variable is, in part, derived from monthly precipitation - where the relationship to daily rain day definition is obviously more convoluted! Our local precipitation expert tells me that, in effect, 'any' precipitation may be used to define a rain day. I think this is taking advantage of rain being measured to one decimal place! Hope that helps, Harry On 14 May 2007, at 7:57, Phil Jones wrote: > >> Date: Sun, 13 May 2007 18:42:37 +0100 >> From: "SP Harrison, Geographical Sciences" >> >> To: p.jones@uea.ac.uk >> Subject: cru ts2.1 >> Originator-Info: login-token=Mulberry:01SIcReq/ >> uhOp7yIrkdq7tPuOA6YediLr9P9yF8Yqedqu1huU=; >> token_authority=postmaster@bristol.ac.uk >> X-Mailer: Mulberry/3.1.5 (Win32) >> X-Spam-Score: -21.4 >> X-Spam-Level: --------------------- >> X-UEA-Spam-Score: 0.0 >> X-UEA-Spam-Level: / >> X-UEA-Spam-Flag: NO >> >> Hi Phil, >> >> No, I am not bugging you about updates -- although it would be >> good to know where you are with this. >> >> Actually, I would like to know what threshold (if any) was applied >> in the definition of a wet day in the CRU TS2.1 data set. I have >> not been able to find this anywhere in the documentation. The >> reason I'm interested is that we are trying to derive wet days >> from GCM output, and I am wondering whether we can use/should use >> the sort of threshold that might be used with real climate data .. >> or whether we should deal with the drizzle problem by setting the >> threshold higher. So the first step is ... what is the threshold >> used in the CRU data sets. >> >> Any thoughts on this would be appreciated ... >> >> Cheers, >> Sandy >> >> ---------------------- >> Professor Sandy P. Harrison >> University of Bristol >> School of Geographical Sciences >> University Road >> Bristol BS8 1SS >> UK >> Sandy.Harrison@bristol.ac.uk >> >> PA - Katie Pellicci >> Katie.Pellicci@bristol.ac.uk > > Prof. Phil Jones > Climatic Research Unit Telephone +44 (0) 1603 592090 > School of Environmental Sciences Fax +44 (0) 1603 507784 > University of East Anglia > Norwich Email p.jones@uea.ac.uk > NR4 7TJ > UK > ---------------------------------------------------------------------- > ------ Ian "Harry" Harris Climatic Research Unit School of Environmental Sciences University of East Anglia Norwich NR4 7TJ United Kingdom