date: Thu Aug 4 13:59:44 2005
from: Phil Jones <p.jonesatXYZxyz.ac.uk>
subject: Re: changes wrt Webster et al
to: Kevin Trenberth <trenbertatXYZxyzr.edu>
These changes are OK. I've made a pdf of the Webster et al doc. I'll send
it with the few others early next week.
I'll try and call later today (say 3pm UK, 8am MT). If you try, I'll be on the phone
sometime between 4-5UK to Dave Griggs. Have to go at 5.30 tonight - 32cnd
Trying to go through Jim's emails, but keep getting interrupted.
On the K and deg C issue, is there a halfway house. What about deg C in
3.1 and 3.9 and the QACCs and K elsewhere? I still reckon I can do this
with a global edit. Need to keep any absolute temps in C though.
I would be happy with all in K except for any absolute ones. I can see
all sides of this point, so as long as we're consistent, we can leave the
final decision to the reviewer's comments.
The call should determine what else there is to do. What we can manage etc?
What are Pielke and Christy up to?
At 00:36 04/08/2005, you wrote:
I have altered two paras:
The last 2 sentence of this para and the last of the second.
Of more direct relevance is the destructiveness of tropical storms, which relates to the
total power dissipation within each storm (Emanuel, 2005), as the main dissipation is
from surface friction and wind stress effects. Consequently it is proportional to the
wind speed cubed. An index of the total power dissipation (Emanuel, 2005) shows
substantial upward trends beginning in the mid 1970s, roughly doubling since then. It
comes about because of longer storm lifetimes and greater storm intensity, and is
strongly correlated with tropical SST. These relationships have been reinforced by
Webster et al. (2005) who found a large increase in numbers and proportion of hurricanes
reaching categories 4 and 5 globally even as total number of cyclones and cyclone days
has decreased in most basins. The largest increase is in the North Pacific, Indian and
Southwest Pacific oceans.
There is a clear El Ni�o connection in most regions, and strong negative correlations
between regions in the Pacific and Atlantic, so that the total tropical storm activity
is more nearly constant than ACE values in any one basin. With El Ni�o the incidence of
hurricanes typically decreases in the Atlantic (Gray, 1984; Bove et al., 1998) and far
western Pacific and Australian regions, while it increases in the central North and
South Pacific and especially in the western North Pacific typhoon region (Gray, 1984;
Lander, 1994; Chan and Liu, 2004; Kuleshov and de Hoedt, 2003), emphasizing the change
in locations for tropical storms to preferentially form and track with ENSO. Formation
and tracks of tropical storms favour either the Australian or South Pacific region
depending on the phase of ENSO (Basher and Zheng, 1995; Kuleshov and de Hoedt, 2003),
and these two regions have been combined. It is also possible to sum the ACE values
over all regions and produce a global value. Although this has been done, it is not
shown, as it is not considered sufficiently reliable. However, by far the highest ACE
year is 1997, when a major El Ni�o event occurred and surface temperatures were the
highest on record (Section 3.2), and this is followed by 1992, a moderate El Ni�o year.
Such years tend to contain low values in the Atlantic, but much higher values in the
Pacific, and they highlight the critical role of SSTs in the distribution and formation
of hurricanes. 1994 is third and 2004 the fourth highest globally in ACE values.
Emanuels (2005) power dissipation index also peaks in the late 1990s about the time of
the 1997-98 El Ni�o for the combined Atlantic and West Pacific regions, although 2004 is
almost as high. Webster et al. (2005) find that numbers of intense (cat. 4 and 5)
hurricanes after 1990 are much greater than from 1970 to 1989.
I am having major trouble with email and I can't do it any other way.
Let me know if you think this is OK?
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.jonesatXYZxyz.ac.uk