date: Fri Jul 8 11:43:30 2005 from: Phil Jones subject: Re: Your hurricane article to: Kevin Trenberth Kevin, Seems that this potential Nature paper may be worth citing, if it does say that GW is having an effect on TC activity. Most odd therefore, the arguments here and those of the BAMS paper, with Pielke Jr and Landsea.. I got the attached from Tom Peterson yesterday. Shows that if you adjust adequately you get the same trends as good stations that haven't changed any routines. I presume some of these poorer sites are those that Pielke Sr. has pictures of. He'll no doubt respond at some time to say that people use the raw data - but clearly one needs to be in possession of all the facts, and not just throw up ones arms and say all is wrong. The US does have good metadata, he will likely say many other countries don't. That is why homogeneity assessments are done. They take a long time, they aren't sexy science and don't get reported in detail. If we wanted a figure for one of the Appendix on this subject (which we don't) this would be a good one to use. When I'm reading there later I'll see if a ref could go in. Problem is that citing one example, opens us to others showing more plots of raw temperatures. Best probably to talk in general terms. Cheers Phil At 18:55 07/07/2005, you wrote: Thanks Kerry A couple of quick responses below. Kerry Emanuel wrote: There is a great deal of confusion on this point in the past, but I thought that had been cleared up by a number of publications. The bottom line is that even in mature hurricanes, most of the water precipitated is advected in, not locally evaporated. But the advected part is irrelevant to the storm energetics (though highly relevant to rainfall). This can be seen from a number of perspectives, but to cut it short, advection cannot change available potential energy; only surface fluxes and radiation can do that. I don't disagree with this at all. But it does say that one has to encompass the entire domain of the storm and its circulation including surrounding areas of subsidence etc: which can even become global. I am familiar with Montgomery's work and it was that which I directly commented on wrt use of axi symmetric storms and how it interacts with the environment. Doesn't seem realistic enough to me. I agree that this does relate to local energy transformations (latent to sensible to kinetic etc) and part of this is simply the different perspectives. All of these things are scientific points that we ought to be able to do better on. I think we have done better than you are giving us credit for.... I think so too, but that is not what it says in the BAMS article. I note your findings that recent trends are towards longer storm lifetimes and toward greater intensity, and that the time series of "total power dissipation" is strongly linked to SSTs. I believe this is fully consistent with my article, and the piece you are missing is water vapor. What drives tropical cyclones..and what we are finding empirically to be the dominant environmental control variable...is the thermodynamic disequilibrium between the surface and the atmosphere. This is related to water vapor through its greenhouse effect. It is perfectly possible to have a dry hurricane, and we have simulated one, if there is enough temperature difference between the surface and boundary layer air and if the surface acts (like the ocean) as an infinite heat capacitor. Of course, the water vapor content per se is highly relevant to storm rainfall. What does that really mean? I don't find "thermodynamic disequilibrium" helpful in terms of talking about change. It relates to ocean atmosphere differences, but only the ocean SSTs and heat content are sort of given by the environment: the atmosphere is determined by the synoptic situation and the storm itself and where it moves. It seems more like a weather terminology and not a climate one. Maybe I am not viwing it correctly but maybe also my confusion can help you clarify what you mean? Finally, let me just say that I am puzzled and disappointed that you are an author on the Pielke et al BAMS article, with its biased rhetoric that does not confine itself to science. There is a story here, which I will tell you in full in August. In brief, I was asked to sign on as a co-author last fall, well before I did the work that is the subject of my Nature article. I refused to sign on because I objected to much of the rhetoric. The lead authors were conciliatory and offered to remove and alter the worst passages. I did agree with one main point...that global warming aside, there are disturbing demographic trends that one needs to worry about with respect to hurricanes. So we went through a series of compromises, and the draft you saw is far better than the one we started with. The price for these revisions is that I agreed to stay on as a co-author, a point I am still not comfortable with. In any event, I think the work in my Nature paper makes it clear (to me, at any rate) that global warming is having a large effect on global TC activity. I also have some new modeling results that support this point, which I will show you in August. Why do you not then withdraw as an author of the BAMS article? All the best, Kerry ______________________________________________ Kerry A. Emanuel Professor of Meteorology Rm. 54-1620, MIT Phone: (617) 253-2462 77 Mass. Ave. Fax: (617) 324-0308 Cambridge, MA 02139 Email: [1]emanuel@texmex.mit.edu Web: [2]http://wind.mit.edu/~emanuel/home.html ______________________________________________ -- **************** Kevin E. Trenberth e-mail: [3]trenbert@ucar.edu Climate Analysis Section, NCAR [4]www.cgd.ucar.edu/cas/ P. O. Box 3000, (303) 497 1318 Boulder, CO 80307 (303) 497 1333 (fax) Street address: 1850 Table Mesa Drive, Boulder, CO 80303 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 ----------------------------------------------------------------------------