date: Tue Apr 15 14:54:23 2008 from: Keith Briffa subject: Re: CRU TS3.0 to: Gerard van der Schrier Gerard First - will you do the first pass at the paper correction - I agree that not that difficult as first thought - but see my previous comments. As for the PDSI and alternative use of Thornthwaite and Penmann-Monteith , I suggested before that this test is perhaps best done using a selection of station tests, selected from "representative regions" where data exist that allow both to be calculated and perhaps where more direct measures of soil water state exist. I take your point about the "calibration" period correcting for some differences , but it is perhaps more valid to worry about the use of Thornthwaite in the first place - there are earlier reviews saying that this is not a good method is certain parts of the world - and this links to your other point re the validity of PDSI or scPDSI in areas of permafrost , heavy snow/lie and very dry areas. Certainly some comparison at sites where actual soil water is directly monitored (Robock Russian work) , surely some sites in US and UK would be available here ? However , the main reason is to explore this and reassess Dai ( criticizing those areas that are invalid for whatever reasons) - and the IPCC map that shows drought world wide (PC1) see attached - did this get into the final report , I need to check. Happy you are still going this way and of course would like to be involved . Ditto that you are happy to work on the 1000-year oak -based reconstruction - centred on Northwest Europe. We will process the oak data and get back to you on this soon. cheers Keith At 10:24 15/04/2008, Gerard van der Schrier wrote: Keith, I've agreed with Ed that I do the PDSI calculations and do some additional quality control tests. Harry will probably keep me updated when he finds more problems with the data. About the Int.J.Clim. paper: I've gone through the remarks you made and which you send me. There are some issues the referees raised, like the infilling of data, which are solved easily. We just have to put more emphasis on the remark we made that infilling is only used for T, the places where P is infilled are flagged as absent and not used in the analysis. I expect that other points are (nearly) as easy. About the Dai paper and other plans with PDSI: the idea is to see if the self-calibrating PDSI is changed dramatically if Penman-Monteith is used rather than Thornthwaite, and i'd like to see a comparison using a complicated and the simple waterbalance model as well. We've discussed this earlier and we don't expect any problems here simply due to the calibrating which probably "adjusts" for any problems with potential evapotranspiration. This should make one paper. The next paper is a global dataset based on the updated CRU data - the rework of Dai's paper. Now that we discuss this topic: I guess we may have problems in regions like the Sahara or Siberia - any ideas yet? We could wait and see how the scPDSI behaves, but is the PDSI a valid index for these regions anyway? Cheers, Gerard Gerard do you wish me to chase this up ? Also can you update me on the Int.J.Clim paper status. Are you considering a rework of the Dai global paper ? Cheers Keith At 08:38 14/04/2008, you wrote: Hi Harry, Sorry to bother you again about the CRU updated data. Ed Cook and myself were wondering about the status of the CRU TS 3.0 data. Is it ready or not yet? We are slightly confused about the status of this update. Some time ago, I received an ftp address for this data and I downloaded the data (both Temp - tx, tg, tn- and Precip). But later, I learned that CRU withdrew support for these data - so I stopped working with these data. Can you tell me where (which continents or which time periods) you suspect most in the dataset I downloaded? (downloaded it at the end of September last year). Or would you advise me not to use the data at all before there is a properly tested dataset? 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 [1]www.knmi.nl/~schrier ---------------------------------------------------------- -- Professor Keith Briffa, Climatic Research Unit University of East Anglia Norwich, NR4 7TJ, U.K. Phone: +44-1603-593909 Fax: +44-1603-507784 [2]http://www.cru.uea.ac.uk/cru/people/briffa/ -- ---------------------------------------------------------- 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 [3]www.knmi.nl/~schrier ---------------------------------------------------------- -- Professor Keith Briffa, Climatic Research Unit University of East Anglia Norwich, NR4 7TJ, U.K. Phone: +44-1603-593909 Fax: +44-1603-507784 [4]http://www.cru.uea.ac.uk/cru/people/briffa/