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A reply to Kooiti Masuda @ RealClimate

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  • Mike Doran
    From RealClimate: 25 I feel that someone in the Western Pacific should say something about storms there, though this is not the area of my expertise. (Typhoon
    Message 1 of 1 , Aug 16, 2005
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      From RealClimate:



      25 I feel that someone in the Western Pacific should say something
      about storms there, though this is not the area of my expertise.
      (Typhoon experts, help!)

      I have browsed the papers of Emanuel (2005) and of Chan and Liu
      (2004).
      (Though my institution has subscription of "Nature", the file of
      Emanuel's paper which I got was an incomplete one --no figures, no
      math formulas, no substantial list of reference. But a complete PDF
      file is available from the author's site at MIT
      (http://wind.mit.edu/~emanuel/home.html ), and a PDF of its
      supplement is also there.)

      Chan and Liu's paper discusses correlation of year-to-year values
      between SST and indices of strong TCs. It is a not study of long-term
      trends. Chan and his colleagues have already discussed the
      relationship between ENSO and Western North Pacific TCs in Wang and
      Chan (2002) and other papers. This time they examine whether local
      SST is important in addition to ENSO, and their answer is "no" in the
      year-to-year time scale. Their story is clearer when variability in
      the longer (interdecadal) time scale is excluded. From that part I
      infer that the correlation between local SST and TC indices is likely
      to be positive in the longer time scale, though it requires a
      specific study to establish such a relationship.

      I am a little surprised to know Chan's previous finding that Western
      Pacific TCs are more active in the El Nino phase of ENSO. My
      understanding which had not been updated since 1980s was that El Nino
      suppresses cumulus convection in the Western Pacific and thus
      suppresses TCs there as well. I still think that the conclusion
      depends on the target area and seasons. Chan and Liu took 120 - 180
      E, May - November. I think that suppression of TCs by El Nino
      prevails in the western part of the Western Pacific, and mainly in
      winter and spring.

      It is true that the area with SST above 27 deg. C in the Central and
      Eastern Pacific is larger in the El Nino phase. Probably the high-SST
      area in the whole Pacific is larger then. But El Nino also tends to
      suppress TCs in some regions where local SST is high enough. Probably
      the correlation between the high-SST area and the total TC activity
      is positive, but it is a result of spatial aggregation of complicated
      phenomena.

      Emanuel (2005) shows the correlation of _smoothed_ time series of SST
      and "Power Dissipation Index". I think that the smoothing reduces the
      ENSO signal, but that it does not eliminate it. Thus it is difficult
      to connect the discussion of the paper with the "ENSO and the rest"
      view of Chan and Liu.

      Emanuel has made a good effort to compensate for the inhomogeneity of
      data quality, as he describes in the supplement. But, it is still a
      difficult issue.
      As Morita and Watanabe (2005) reported, the "best track" data shows
      decrease of the frequency of strong TCs in the 1990s in the area 15-
      30 N, 120-150 E.
      (Morita refers to a data set compiled by Japan Meteorological Agency.
      I think it is essentially the same as the Western Pacific part of the
      JTWC data set used by Emanuel and by Chan, but I have not confirmed
      it.)
      In some more detail, TCs with central pressure lower than 920 hPa
      decreased, those around 950 hPa increased, and those around 980 hPa
      decreased. Though it cannot be denied that these are real trends,
      Morita suspects that these are artifacts due to changes in observing
      practice. Aircraft reconnaissance in the Pacific was phased out in
      1987, and since then surface pressure have been determined by
      satellite image interpretation (Dvorak method) except occasionally by
      island stations or ships. Morita's results suggest that the image
      interpretation underestimates very strong TCs (typhoons) but somewhat
      overestimates moderate ones (TSs). I am not sure whether this causes
      significant bias in Emanuel's PDI. Also, Morita's observation is
      about the specific region. Dvorak method may have different
      sensitivity in different climatic regions.

      When we discuss whether the influence of global warming has appeared
      in TCs, there is a fundamental problem that we are not very sure
      about theoretically how TCs should react to (greenhouse-gas-induced)
      global warming.

      For middle latitudes, extratropical cyclones are the principal actor
      in the energy cycle in the atmosphere. Therefore the total power of
      cyclones (the number times the intensity) in the whole mid-latitude
      zone should somehow correspond to the global forcing. If the
      characteristics of transient warming is similar to those of
      equilibrium warming, the north-south gradient of temperature will
      decease, and therefore the total power of extratropical cyclones will
      decrease.
      (Things may not be so simple, however, even in this zone. Increased
      water vapor will provide energy by latent heat release and somewhat
      compensate for the loss. And perhaps more important role of
      moistening is to increase inhomogeneity within individual cyclones.
      Surely the maximum rainfall rate will increase. Also the maximum wind
      speed may increase despite of decreased average value.)

      There is no guarantee for such large-scale determinism for TCs. The
      essential feature of the tropical atmosphere is cumulus convection,
      whose individual horizontal scale and time scale are of the order of
      1 km and of hours. The largest-scale feature is the Hadley
      circulation whose upward branch is none other than the collective
      activity of cumulus convection. The Hadley circulation requires
      cumulus convection, but it does not require TCs. Whether cumuli
      organize into TCs, easterly waves, Madden-Julian oscillations or
      something else, or maybe remain rather random, is not constrained by
      global-scale forcing.

      If we assume large-scale determinism, we can have some conclusions
      which will be valid as long as the assumption is valid. Emanuel's
      previous theoretical work (Emanuel, 1987) assumes that there is a
      circular vortex coupled with convection, and discusses how strong it
      would be. The GFDL model has more degree of freedom, but their
      experiments assume a circular vortex as the initial condition. It is
      reasonable that results of these studies are mutually consistent.

      Global warming experiments with a "20 km grid" (actually spectral)
      GCM of the Meteorological Research Institute (MRI, of Japan) shows
      intensification of strong TCs (consistent with the GFDL model study),
      and increase of the life time of individual TCs (as Emanuel
      suggests), but also decrease of the total number of tropical storms.
      (Unfortunately the only on-line information about that study I have
      found is a short abstract for the previous AMS meeting (Oouchi et
      al., 2005). Off-line and in Japanese, there is a little more
      information in the abstract volume of MSJ 2005 Spring Meeting
      (presentation Nos. A203 and A204)).
      I am not sure whether the collective total power of TCs, or Emanuel's
      PDI, increases or decreases as climate warms in that model.

      A caveat is that all GCMs as well many TC models (including GFDL's)
      that have been used for climate change experiments employ hydrostatic
      approximation and "cumulus parameterization". They assume some ways
      of self-organization of cumulus convection which may or may not be
      true. Non-hydrostatic, cloud-resolving models are promising in
      reduction of this kind of uncertainty. But, climate simulation with
      these models requires much more computer resources than currently
      available. Whether the society can afford the cost is another problem.

      Another difficulty for the 21st-century projection of TCs (and also
      for the projection of tropical climate in general) is that it is not
      certain how ENSO behaves as the mean climate warms. With the same
      scenario of greenhouse gas concentration, some coupled GCMs produce
      more EN-like climate, and others less EN-like. ENSO may be a kind
      of "free" mode which can shift either way.

      We can say some small thing relatively confidently for those mid-
      latitude areas which are sometimes affected by TCs. Warmer _local_
      SST helps maintain TCs which happen to arrive there. Thus, we will
      encounter more cases of strong TCs there _unless_ the situation at
      the area of TC generation changes much.

      References added
      * Emanuel K.A., 1987:
      The dependence of hurricane intensity on climate.
      Nature, 326, 483-485.
      * Morita M. and Watanabe S., 2005:
      On a problematic issue of the Dvorak method for observations of
      typhoons---Have typhoons really become weaker than before? (in
      Japanese)
      Meteorol. Soc. Japan 2005 Spring Meeting, Presentation No. C201.
      * Oouchi K., Yoshimura J., Yoshimura H., Mizuta R. and Noda A., 2005:
      Tropical cyclones in a greenhouse-warmed climate: a projection from a
      20-km mesh global climate model.
      Amer. Meteorol. Soc. 2005 Annual Meeting, Suki Manabe Symposium, P1.1.
      http://ams.confex.com/ams/Annual2005/techprogram/paper_86839.htm
      * Wang, B. and Chan J.C.L., 2002:
      How strong ENSO events affect tropical storm activity over the
      western North Pacific?
      J. Climate, 15, 1643 - 1658.

      Comment by Kooiti Masuda — 16 Aug 2005 @ 4:56 pm

      MY RESPONSE:

      25. Kooiti Masuda

      I have to write again about event horizons. The global computer
      models are crap for more than a lack of computing power. Even if the
      computer was as large as the earth itself, it would be GIGO.

      If your change your set of assumptions there is another way.

      It is essential to discuss event horizons in climate.

      For instance the Dane research on cosmic ray flux--with glacial
      epochs associated with the movement of the solar system up and down
      in the plane of the galaxy--this is a good example of an event
      horizon that has long term climate predictability. The spinning of a
      hurricane--you cannot even predict mesovortices an hour ahead of time-
      -so now you want to use the same event horizon and explain what is
      happening now, what is happening 100 years from now? Terrible.
      Junkscience! The math shows you that turbulance and viscosity limit
      future behavioral prediction. So we have to look at other mechanisms
      that we know with certainty have predictable event horizons. But
      then the critical comments here are that with warmer climates come
      different baratropical behaviors. It's the same problem, stated
      differently. The idea of ENSO as a factor is a better approach,
      because the timescale of ENSO has a longer event horizon, and there
      are correlations of ENSO with tropical storm activity. Then there is
      the SSTs, which again is the same problem--as they too haven't
      necessarily been directly associated with increases in both intesity
      and frequency of tropical storms.


      So let me digress a moment and come back to this. The weather
      community is dominated by those who study and consider baratropical
      behaviors--as well as they practically should. However, the viscosity
      issue becomes dominate over longer timescales--where ELECTRICAL
      influences on cloud microphysics start to dominate. The turbulance
      problem is then like talking about turbulance of the water in a pipe--
      all you need to really talk about is the pipe to know where the water
      is going to go. And while large scale electrical features hold the
      key, none of the so called 'skeptics' have looked at electrical
      behaviors as it pertains to climate--as they are not trained as such:

      http://groups.yahoo.com/group/methanehydrateclub/message/1816

      Of course, meteorologists are also lacking in such training. And I
      say this with real respect, as my father himself is a meteorologist
      and I was born on in the early sixties on an Air Force base where he
      gave weather to the SAC pilots flying B-52s. Pure respect for this
      profession--but it isn't a profession where there is training in
      EMFs.

      Finally there are the 'warmers', and they too approach the problem of
      cloud dynamics as a direct feedback heating. They tend to, if they
      have education on what the GHG physics really are, a corresponding
      lacking education in electro magnetic behaviors, and specifically
      what electro magnatic properties CO2 has in the oceans.

      ENSO itself because it is a longer time scale cloud dynamics behavior
      is ELECTRICALLY forced. The SOI is largely about the relative
      depressurization and stirring of the oceans either over Darwin or
      Tahiti and then one end gets discharged, like a flat beer, per Bates
      et al Nature on Hurricane Felix, and the conductivity dynamic changes
      and capacitive couplings between ocean and ionosphere which organize
      cloud microphysics flips back to the other end of the tropical
      Pacific. Where ENSO comes in is the sustained winds start to have
      induction meaning with the moving salt spray and surface, and, again,
      SSTs factor in about a drop in one percent of resistance per increase
      of one degF. For purposes of this discussion, I will leave out cold
      upwelling of initially more resistive water, but that same water
      contains nutrients for large scale biological conductivity factoring
      here, and I will also leave out space weather, and its implications
      on the ionosphere and the capacitive couplings involved.

      I will only talk about ENSO in terms of CO2 and the general
      temperature of the Pacific. This is critical because ENSO really has
      only been around in the 2 to 7 year peridicity for only 5,000 years.
      You go into the Wisconsonian and El Nino may come every 20 years or
      not at all. Then it comes up in still other climates long ago, but
      the point is, the oceans warmed, CO2 increased, and ENSO came. If
      you think only about the problem thermally, only think about the
      oceans warming overall, it doesn't really provide explaination for
      what ENSO 'is', or why it came about 5,000 years ago, and not, say,
      12,000 years ago or 8,000 years ago during other warm periods
      preceeding the Wisconsonian.

      But an electrical view reveals mechanism of the climate change. As
      the oceans warm up, the induction meaning of the sustained winds
      along the tropics starts to become more significant relative to
      capacitive couplings of ocean and ionosphere. It has to because
      induction has to overcome the relative conductivity changes that
      occur from the SOI depressurizing and stirring one end of the Pacific
      while the other recharges. Eventually one end gets 'flat' from
      carbination coming out of solution and the other end is more prone to
      microphysics organizations and hence pressure changes.

      When an El Nino event occurs, its induction meaning is so significant
      and such a concentration of the energies of the global electrical
      circuit that other areas cannot be so organized. That's why
      hurricanes won't occur as well during an El Nino.

      Now, the idea that there is a different event horizon with and
      electrical approach should be more clear. That is, no matter weather
      now or 100 years from now, CO2 concentrations will have very specific
      conductivity meaning as it comes out of solution from the low
      pressure and winds of a tropical low, where it rises to the ocean
      surface and then goes back there into solution and rises ion counts--
      exactly where capacitive couplings with the ionosphere then occur and
      alter cloud microphysics in the more intense field and relatively
      organize a tropical storm.
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