date: Tue, 22 May 2007 19:10:10 -0400 from: "Zwiers,Francis [Ontario]" subject: RE: 5AR runs next iteration- reply by 26th to: "Gabi Hegerl" , "myles" , "Tim Barnett" , "Nathan Gillett" , "Phil Jones" , "David Karoly" , "Jesse Kenyon" , "Reto Knutti" , "Tom Knutson" , "Toru Nozawa" , "Doug Nychka" , "Claudia Tebaldi" , "Ben Santer" , "Richard Smith" , "Daithi Stone" , "Stott, Peter" , "Michael Wehner" , "Zhang,Xuebin [Ontario]" , "Hans von Storch" , "Karl Taylor" Hi all, Sorry for my late response, and also, I apologize if I mention things here already mentioned by others. I have a few comments on Gabi's list ... Start date: I think 1950 would be good, which would allow us continue to usefully do detection on a 50+ year period. This is important, particularly for variables where signal-to-noise ratio is lower (e.g., one can anticipate a lot more work on extremes, and on precip for the AR5). I agree that starting from lower resolution climate of the 20th century runs would probably be preferable to starting from observed intial states. There is the issue of lack of initial spread that Gabi mentions, but also the problem of the ocean models drifting back to their own climates over the initial few decades - an effect that would be confounded with the response to forcing that we would be interested in. For the lower resolution century runs, an 1850 start date would be ok, although I can see arguments for starting earlier. It depends upon how much can be sold to those who have to do the runs. Internal varibility: I think this is going to be a difficult problem. Intra-ensemble variability will give some information, but perhaps not enough, particularly given that we probably have to continue to use dimension reduction approaches, and thus will need to divide whatever internal variability information we have into two samples. Perhaps it will be possible to use lower resolution controls if we can demonstrate that their rendition of internal variability is indistiguishable from that inferred from higher resolution late 20th century ensembles at the scales that we retain in D&A analyses. Another option might be to determine whether we can estimate the high resolution internal variability by appropriately scaling lower resolution estimates of internal variability. We probably need to give some thought to exactly how we would use high res runs for climate change detection given that the fine features in these runs could be filtered out when we use standard dimension reduction approaches. Variables saved: I'm fine with the list, but would urge 50+ years, 1950 onwards. We should add vertically integrated specific humidity to the list (monthly probably ok). What about other things to close the hydrological cycle (run off, evaporation) and some things related to the cryosphere (e.g., snow cover, snow mass, sea ice extent, and to the extent that they are included, mass balance for ice sheets, ice caps, glaciers). Regarding lowest model level winds, or 10m winds ... There can be quite a difference between these two, so we should probably specify the 10m level? A problem is that the 10m wind is a diagnosed quantity, so I think it would be good if the use of a standard scheme for diagnosing the 10-m wind were requested (I think as is done for pmsl). Tuning against the 20th century evolution: The quick reaction I got from folks here was that it was simply still too expensive to generally take that approach, and they couldn't quite conceive of what one might adjust. Those with experience with QUMP like approaches would probably have more insight, and thus are already implicitly doing a bit of tuning of this type. We probably can't legislate against it. As a community, we use a hierarchy of models, and the dividing line between models for which one can and cannot feasibly tune against the 20th century evolution is presumably a function of computing cost (which is reducing for an given level of model complexity) and model formulation. The computing boundary is certainly moving towards making this feasible for more complex models. Whether tuning is desirable presumably depends upon the objective of the modelling exercise. I hope this is useful. If you eventually get this, it means that my current e-mail problems have finally be resolved by our tech support types in Toronto :). Cheers, Francis Francis Zwiers Director, Climate Research Division, Environment Canada Toronto: 4905 Dufferin St., Toronto, Ont. M3H 5T4 Phone: (416)739-4767, Fax: (416)739-5700 Victoria: PO Box 1700, STN CSC, Victoria, BC, V8W 2Y2 Phone: (250)363-8229, Fax: (250) 363-8247 -----Original Message----- From: Gabi Hegerl [mailto:hegerl@duke.edu] Sent: Friday, May 18, 2007 10:34 AM To: myles; Tim Barnett; Nathan Gillett; Phil Jones; David Karoly; Jesse Kenyon; Reto Knutti; Tom Knutson; Toru Nozawa; Doug Nychka; Claudia Tebaldi; Ben Santer; Richard Smith; Daithi Stone; Stott, Peter; Michael Wehner; Zhang,Xuebin [Ontario]; Zwiers,Francis [Ontario]; Gabi Hegerl; Hans von Storch; Karl Taylor Subject: 5AR runs next iteration- reply by 26th Hi all. From your comments, I assembled a word file with our suggestions on the 5AR run proposal, but I am not sure I caught it all completely. Also, I had a chat with Jerry yesterday, and he said getting suggestions of what should be stored will be useful at this point. My plan is to communicate this with Jerry when we are done with it, and then propose it at the WGCM meeting. I drew a strawman list of what I could think of in 3 minutes, and am asking you to add to it. Its all in track changes, so dont hesitate to go wild (but please keep in mind that we need to restrict data requests to something you think you will work with in the next years, since it is a fair amount of effort from the modelling centres to haul the data over etc, and the more we request, the more likely it is that only few ensemble members etc get sent...) Karl, I am cc;ing you since your perspective would be useful Gabi -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Gabriele Hegerl Division of Earth and Ocean Sciences, Nicholas School for the Environment and Earth Sciences, Box 90227 Duke University, Durham NC 27708 Ph: 919 684 6167, fax 684 5833 email: hegerl@duke.edu, http://www.env.duke.edu/faculty/bios/hegerl.html