by Judith Curry
Peter Webster’s magnum opus is now published: Dynamics of the Tropical Atmosphere and Oceans.
From the blurb on amazon.com:
“This book presents a unique and comprehensive view of the fundamental dynamical and thermodynamic principles underlying the large circulations of the coupled ocean-atmosphere system
Dynamics of The Tropical Atmosphere and Oceans provides a detailed description of macroscale tropical circulation systems such as the monsoon, the Hadley and Walker Circulations, El Niño, and the tropical ocean warm pool. These macroscale circulations interact with a myriad of higher frequency systems, ranging from convective cloud systems to migrating equatorial waves that attend the low-frequency background flow.
A comprehensive overview of the dynamics and thermodynamics of large-scale tropical atmosphere and oceans is presented using both a “reductionist” and “holistic” perspectives of the coupled tropical system. The reductionist perspective provides a detailed description of the individual elements of the ocean and atmospheric circulations. The physical nature of each component of the tropical circulation such as the Hadley and Walker circulations, the monsoon, the incursion of extratropical phenomena into the tropics, precipitation distributions, equatorial waves and disturbances described in detail. The holistic perspective provides a physical description of how the collection of the individual components produces the observed tropical weather and climate. How the collective tropical processes determine the tropical circulation and their role in global weather and climate is provided in a series of overlapping theoretical and modelling constructs.
Following a detailed description of tropical phenomenology, the reader is introduced to dynamical and thermodynamical constraints that guide the planetary climate and establish a critical role for the tropics. Equatorial wave theory is developed for simple and complex background flows, including the critical role played by moist processes. The manner in which the tropics and the extratropics interact is then described, followed by a discussion of the physics behind the subtropical and near-equatorial precipitation including arid regions. The El Niño phenomena and the monsoon circulations are discussed, including their covariance and predictability. Finally, the changing structure of the tropics is discussed in terms of the extent of the tropical ocean warm pool and its relationship to the intensity of global convection and climate change.”
The complete table of contents are found here [Table of Contents]
JC remarks
My minor role in this was to help edit the final drafts of the chapters, so I have been through the entire book with a very detailed read.
Here is what stands out for me in the book.
First, the book is ‘old school’ in the sense of integrating observations and theory. This approach is surprisingly rare these days in climate dynamics, with its heavy reliance on global climate model simulations. The book has a very strong foundation in fluid dynamics and wave dynamics. At the same time, the mathematical developments are sufficiently clear to be followed by students, with additional details in the appendices.
Second, the book presents an underlying philosophy for approaching the understanding of tropical dynamics, integrating reductionist and holistic approaches.
Third, the book provides historical context for the development of our understanding. Interesting historical snippets are provided, including biographical notes of key historical scientists.
Fourth, the above three elements integrate to provide insights into the process of the science of climate dynamics, not merely a recitation of our current understanding
Fifth, there are over 300 diagrams/figures in the book, including many originally drawn schematics that are very effective at providing insights and supporting understanding. An example is provided below:
Figure 14.30 Schematic of the sequence of events in 1997–1998. (a) The climatological alongshore winds off Sumatra (E) and the east African coast (F). The winds observed in the late summers and early autumns are denoted by G and H, respectively. The right-hand panel shows the effect at the equator on the upper ocean induced by increased upwelling in the east and decreased upwelling in the west. Wind into and out of the plane of the page are denoted by the bull’s-eye and cross-hair symbols, respectively. (b) Distribution of the winds resulting from the anomalous SST gradient along the Equator and the changes in the SSH distribution. (c) Formation of the Ekman ridge in the central Indian Ocean and the forcing of westward-propagating downwelling equatorial Rossby waves to the west. The right-hand panel shows the effect on the upper ocean near 5°S. (d) Subsequent cooling of the western Indian Ocean through enhanced mixing and coastal Ekman transports from stronger than average monsoon winds and through circulation changes associated with the weakening of the 1997–1998 El Niño.
The next section provides the complete text from the concluding chapter.
Chapter 19 Some Concluding Remarks
When I entered graduate school in the late 1960s, my advisor at the time had just completed a treatise entitled “Some remaining problems in numerical weather prediction” (Charney 1967). Five problems were described and referred to as:
…. certain islands of resistance which seem to hold out stubbornly in the face of all attacks.…
Broadly speaking these issues were:
- What is the relationship between the turbulent boundary layer and synoptic scale variability?
- How can steep gradients associated with fronts and topographic features be handled in models?
- Do models correctly handle the cascade of energy between scales of motion?
- How are convective processes and large-scale tropical circulations related?
- What determines the structure, variability, and location of such preeminent tropical features as the ITCZ organized and maintained?
Charney’s paper deeply depressed me! Here I was, a brand new student in graduate school embarking on a career in tropical meteorology surrounded by bright and eager graduate students, all of whom seemed to know what they were doing, a faculty that was acknowledged as the world leaders in atmospheric science, and only a handful of questions remained. Clearly all of these would be answered by the end of the semester. This made me wonder whether I should have gone to medical school after all.
Now, over 45 years later, many new questions regarding the tropical system have arisen. It is interesting, though, to determine what progress has been made in solving Charney’s list of problems and how we have approached their solution.
Understanding complex natural phenomena has generally been undertaken by following a reductionist approach, whereby a phenomenon’s complex nature is reduced into individual components that are assumed to work together to produce observed structures. Reductionism evolved from Rene Descartes’ “mechanical philosophy,” whereby the universe is thought of as a complicated machine made up of identifiable components. Essentially, reductionism aims to understand the nature of complex things by reducing them to the interactions of their parts, or to simpler or more fundamental components. This implies that a complex system is nothing but the sum of its parts. Chapters 6 and 7 adopted a reductionist approach in attempting to explain tropical variability in terms of fundamental linear equatorially trapped modes. This modal structure formed the basic explanations of intraseasonal variability (Chapter 15) and the coupled ocean–atmosphere ENSO and Indian Ocean Dipole (Chapter 14). And, to some degree, the behavior of many of these large scale systems circulation systems may be identified as combinations of fundamental components of the ocean–atmosphere system.
However, when it comes to predicting the state of a complex system, we find that the reductionist approach does not help in the prediction of emergent (or unforeseen) phenomena. If the climate system were purely a combination of linear modes, then prediction would be a much simpler endeavor, with the main challenge being to reduce the impact of inaccuracies in the initial fields that may introduce uncertainty into a prediction. Yet extended weather and climate prediction has proven to be universally difficult. For example, even though in Chapter 14 we pointed out that the basic components of ocean–atmosphere interaction are basically understood, each ENSO event (the supposed sum of these parts or components) is very different both in timing, duration, and amplitude. Predictions of whether or not an El Niño or La Niña event will develop following the boreal spring show little skill. Also, it is difficult to assess whether or not a La Niña will be followed by an El Niño or vice versa. Once an ENSO event develops in the early boreal summer, it tends to follow its own trajectory, which may be similar or somewhat different to other El Niño or La Niña events.
Similar differences between the characteristics of individual circulation events exist on subseasonal time scales as well. As with ENSO, much of the structure of intraseasonal events features can be recognized in terms of fundamental equatorial modes whereby convection has been accounted for in some manner. Each MJO has an individual character. Even the canonical MJO, forming in the equatorial Indian Ocean, varies from case to case.
In Chapter 11 (also Chapters 13 to 18), it was argued that a more holistic approach was necessary in order to understand the complex nature of the Earth system. Holism claims that complex systems are inherently irreducible and are more than the sum of their parts, owing to chaos and nonlinearities. Emergent behavior may arise from complex systems that cannot be deduced from consideration of the components of the system alone. Holism leads to “systems thinking” and possesses derivatives such as chaos and complexity. This discussion grew from attempts to understand interactions between the extratropics and the tropics. In Chapter 9 it was argued that extratropical waves had difficulty propagating through zonally symmetric easterlies toward the equator so that more complex explanations were necessary to explain extratropical–tropical interactions. In Chapter 10, it was found that a zonally symmetric Hadley Circulation could not explain fully the influence of the tropics on the extratropics or vice versa. Yet progress was made toward understanding the interaction between the tropics and the extratropics by noting the interaction of two nonlinear systems, one being the divergent circulations transporting PV poleward and the other, the Rossby wave regime, returning the PV to the tropics.
The predictability of complex systems can be described using concepts introduced by Hofstadter (1980). Simply stated, system predictive skill depends on its degree of complexity. Three hierarchies of organization and disorganization are suggested: simple, complex, and tangled, where the simpler the complexity the greater the potential predictability. By extension, the more complex the system, the less predictability the system possesses.
- A simple system possesses two components, A forcing B or two interacting bodies as in the classical “two-body” problem such as the interaction of a planet and its moon. Variability of the predictive outcome arises only from the uncertainty of describing either A or B. An example of a simple system is the lunar forcing of ocean tides and its high predictability.
- The introduction of a third component (C) produces a complex system and introduces uncertainty into how the three components (A, B, and C) interact. First, initial conditions require a description of the system now extended to three components instead of two thus adding further uncertainty. Further, the system trajectory may be very different depending on the initial scale of each of the three components or its initial magnitude.
- The most complex system, tangled, may have multiple interacting components (C, D, …, etc.). The climate system itself is such an example, with interacting oceans, atmosphere, cryosphere, and land systems.
Specific circulation patterns in the climate system may be complex or tangled. The existence of some predictability of an ENSO extrema, once it is initiated, suggests that the system is complex and probably not tangled. Similarly, the wider influence of ENSO is a complex system since some predictability is retained. However, the lack of persistence or predictability across the boreal spring suggests that at longer time horizons, or at certain times of the year, the ENSO system would appear to be tangled and unpredictable. Over the course of an annual cycle, though, the system moves from tangled to complex as it changes from frail to more robust, as discussed in Chapter 14.
Hence predictability of a system depends on a number of factors:
- The degree to which the initial conditions of the system are known.
- How well A and B are understood physically and represented by a model (either empirical or numerical).
- How large and variable is component C (or D and E …)? Are they stochastic? Does one element or one process dominate over all others? For example, the solar system is a complex multi-body system but the Sun’s gravitation makes it (almost) a stable system as it represents 98% of the mass of the solar system and, thus, chaotic motion of the planets is rare.
Given these points, it is tempting to adopt a holistic approach to the prediction of tropical phenomena by resorting to complicated coupled ocean–atmosphere–land models. However, given model formulation and initial data uncertainties, it is necessary to use a probabilistic approach in which the model is perturbed many times to produce an ensemble of forecasts. It is also clear that a hierarchy of methods are needed to increase understanding and predictive capability, including both holistic and reductionist approaches. If the components of a complex system can be identified and it can be determined that component C, for example, is more dominant at some stage of the prediction than another, one may be able to anticipate confidence in the results of the probabilistic forecast.
As discussed above, understanding of the interaction of the tropics and extratropics could only have been developed through a holistic or system approach. The behavior of an individual component (the collective divergent circulations or the recurring Rossby waves families) could not have led to a determination of the synergies between the tropics and extratropics. Instead, we gained an understanding by applying the Haynes and McIntyre impermeability theorem that constrained the advection of a potential vorticity substance between the tropics and the extratropics or, specifically, across a latitude circle. It could be that other difficult problems, such as why there is little difference in annual precipitation (rate or volume) of each hemisphere, will be understood through similar system constraints.
So, what can we say about the problems Charney laid out in 1967? There has been substantial progress in the first two problems. In 1967, the grid point resolution of the earliest numerical weather models was hundreds of kilometers. Now it is closer to 10 km and will possess greater resolutions and become cloud resolving in the near future. The number of vertical levels has increased as well from only a few to over 50 in some operational models. Topographic relief is incorporated directly through use of the sigma-coordinate system. However, Charney’s third and fourth problems remain “islands of resistance” to this day. Simply, we still are uncertain about how equatorial dynamics and convection interact and the degree of their mutual dependency. With respect to the ITCZ, Section 13.1 offered six theories regarding the location of equatorial convection. Although some are stronger than others, their number is an indication that closure on the issue has not yet been reached. In addition, we have unearthed many new mysteries. One is the discovery of enclaves of disturbances existing within tropics made up of families of convection ranging from diurnal through synoptic and biweekly to intraseasonal.
In retrospect, Charney’s tropical problems were not solved by the end of the semester, nor by the end of the decade, and not even in the present time. In fact, investigations of these problems have spawned many new exciting problems. It seems that I was needlessly depressed in 1967 about the future opportunities in tropical meteorology.
With these many unsolved problems, how can there still be 97% consensus that climate science is settled.
A consensus only requires agreement between parties on any topic. Science is not involved in coming to a consensus in any way shape or form other than a consensus can be made on any topic including science.
“how can there still be 97% consensus that climate science is settled”
The myth perpetuated.
What is “settled” is that the Earth’s climate is warming, and it is doing so because of anthro injection of CO2 into the atmosphere.
All else. including the sensitively of climate to said GHG, is still under study.
I think everyone can agree it’s complicated.
But we in Ice Age Or and we have cold ocean {3.5 C}
And are mostly recovering from cooler period which called
The Little Ice Age.
Little Ice Age inside a +million year Ice Age.
And we should be thankful for any warming we get.
Not a mention of solar wind variability and ENSO of course.
Try reading the table of contents there is tons on ENSO
Nothing on the solar wind. The Sun drives ocean cycles and weather extremes, and lots of bright people who don’t know that do some very clever things with fluid dynamics, but cannot predict much.
Congratulations to Peter and you.
And from me
I bought the eBook for my Kindle. It looks like quite an accomplishment.
not content to buy one expensive book, I splurged on both the Kindle edition and the hard copy. I have not had the Kindle long, and I am experimenting with it.
Reblogged this on uwerolandgross.
…and the book is available to Climate Etc readers at the reduced price of….
Tonyb
“Cristobal is forecast to intensify and become post-tropical later today as the energetic upper trough approaches from the west. Winds are forecast to reach gale force over the waters of the Great Lakes as the post-tropical cyclone passes in a close distance early on Wednesday. Heavy downpours can also be expected near the track of Cristobal. The Great Lakes will continue to see showery and windy conditions into Wednesday as the complex system intensifies further and heads into eastern Canada early on Thursday.”
Yikes! Another expensive book.
facetiousness aside, it is a book I look forward to studying.
“The most complex system, tangled, may have multiple interacting components (C, D, …, etc.). The climate system itself is such an example, with interacting oceans, atmosphere, cryosphere, and land systems.”
In this case it’s possible the etc. continues ad infinitum.
Thank you for this. Like a textbook. Learned a lot. Took notes. Btw we are having a bitterly cold June in Thailand. It does warm up in the afternoon right up until the dark clouds start to form in the western sky. We don’t need the air conditioner to sleep at night. We need blankets.
I’d be curious if Peter or Judith has any insight into the tropical convection issue. I believe that detailed simulations will remain very challenging for the forseeable future, but it looks to me as if the evidence indicates that we are missing something with regard to vertical temperature and humidity profiles in the tropics. I also am worried that the moist adiabat theory is perhaps quite flawed. It might be possible to study this issue computationally on a relatively small domain with periodic boundary conditions.
Hi,
Good point. Give me the rest of the day and I will comment.
Peter
Paul Pukite:
https://openreview.net/forum?id=XqOseg0L9Q
Two pp of hand-waving; We are supposed to take that seriously?
And this: In this chapter we describe deterministic and stochastic models of oceanic wave energy. In addition to tidal dynamics, a novel deterministic model of the behavior known as the El Nino‐Southern Oscillation of the equatorial Pacific Ocean is presented
That could potentially be interesting; do you have an open source? Hopefully (?) it’ll be better than what you have written on your web page. $42 for a book chapter is steep.
You’re not doing anything close to the simplified model of Navier-Stokes that comprehensively maps all of the climate indices.
Nor does it claim to. What an idiotic sentence that is!
Paul Pukite: The best that the clueless statistician can do is complain about the cost of scientific publications.
that’s NOT all: I bought a copy of Peter Webster’s book and I asked if you had an open source publication I could read. Actually, it would not have to be open source, but I haven’t found your book chapter. You claim the state of the art was published 2 years ago: any other references? I’ll read them — I read (at least some of) almost everything that is linked or referenced here. My book collection is growing.
Aside from your own work, is there a better book?
Your comment refers to shallow basins: Do tropical dynamics happen in a shallow basin?
My general rule is that people who are rude and toss around adhominems are usually not trustworthy on technical subjects. That’s even more true if they constantly tout their own “work”.
Paul Pukite, about my question: Aside from your own work, is there a better book?
Please let me rephrase. What are the inaccuracies in Webster’s presentation that you have improved upon, and where can I read those improvements?
Webbie
Nice to see you’re back. Having you…..and a few others….around here gives me great comfort that I’m on the proper side of the issue. Keep on being…..well…. real.
dpy6629: My general rule is that people who are rude and toss around adhominems are usually not trustworthy on technical subjects.
In my experience, Paul Pukite’s criticisms are usually vague or wrong, but it is worthwhile to read them and examine in what respect(s) they may be wrong.
“Charney’s third and fourth problems remain “islands of resistance” to this day. Simply, we still are uncertain about how equatorial dynamics and convection interact and the degree of their mutual dependency. With respect to the ITCZ, Section 13.1 offered six theories regarding the location of equatorial convection. Although some are stronger than others, their number is an indication that closure on the issue has not yet been reached. In addition, we have unearthed many new mysteries. One is the discovery of enclaves of disturbances existing within tropics made up of families of convection ranging from diurnal through synoptic and biweekly to intraseasonal”.
At least it explains how I could be so wrong in assuming we would have a lower temperature for May UHS.
Instead of blaming Roy I will console myself with “enclaves of disturbances existing within tropics made up of families of convection ranging from diurnal through synoptic and biweekly to intraseasonal.”
Such is life.
Perhaps he/I will get it right in June.
angech, perhaps so. The bump in May still leaves temps moderate, and erased the summer NH heat wave, concentrated over Russia. IMO, cooling more likely
https://rclutz.wordpress.com/2020/06/05/moderate-may-for-land-and-ocean-air-temps/
Always pick the graph that lifts your spirits the most.
At the moment moyhu nick is doing this with his monthly NECP which is showing , sigh, 1 week of low temps.
Tropical ocean temps also seem a bit lower.
Sadly these sprigs of green have always wilted in the past.
Keep up your good work with the ocean temp reviews and cross those science fingers for the natural cycles to kick in.
–
Thanks for the new book mention , Judith.
“As discussed above, understanding of the interaction of the tropics and extratropics could only have been developed through a holistic or system approach.”
As an undergrad, I was struck by the observation that intense polar air masses tracked across the equator. There’s no brick wall separating the tropics and extra-tropics. Indeed, the conceptual model of Marcel LeRoux conceives of the convergence of the ITCZ resulting from the convergence of opposing surface polar air masses. The thermal gradients of these polar air masses decrease from the modification along their paths and the morphology of these polar air masses become elongated and more shallow, which is physically implied by the path effect of vorticity and Coriolis as masses traverse to the equator. Consequently, polar air masses converging at the ITCZ are limited to the lowest levels, indistinct and not well identified. LeRoux describes these masses as also being ‘agglutinated’. These masses are not well identified, but physics do indicate that tropical convection necessarily occurs from the conditional instability of the lowest layers.
The descriptions of LeRoux are qualitative without equations, so they don’t get much traction. But they are appealing because they unify tropical and extra-tropical phenomena in such a holistic framework.
https://www.skyfall.fr/wp-content/2014/07/17.png
Turbulent Eddie: The descriptions of LeRoux are qualitative without equations, so they don’t get much traction. But they are appealing because they unify tropical and extra-tropical phenomena in such a holistic framework.
I liked his book Dynamic Analysis of Weather and Climate. It has many narrations of processes that traverse many lattitudes and longitudes, along with photos and diagrams, and measurements of aspects of the processes, like wind speeds, rainfalls, and so forth. I mention these things, following your lead, because I think they give a better sense of “what’s really happening” than the more mathematical/modeling accounts that I spend more time reading.
Along this line, chapter 13.1.2.5 of the book cites Philander, who authored:
Why the ITCZ is mostly north of the equator
Chapter 13.1.2.5 says Philander’s theory indicates:
“it is the configuration of the continents that determine at which longitudes the interactions are effective”
This has great relevance to climate change models, given that the GCMs continue to create the “double-ITCZ” which is not observed.
(The Double‐ITCZ Bias in CMIP3, CMIP5, and CMIP6 Models Based on Annual Mean Precipitation)
Doubled tropical convection probably also biases water vapor feedback too high.
Are the parameterizations of tropical convection fubar?
“With respect to the ITCZ, Section 13.1 offered six theories regarding the location of equatorial convection.”
I haven’t yet perused 13.1, but LeRoux’s conceptual model explains two aspects of ITCZ location very well.
1. The failure of the ITCZ to appear in the SH of the Eastern Pacific is explained by the Andes’ North-South alignment which channels the shallow Southern polar air masses directly toward the equator, while in the NH, polar air masses encounter the Rockies some 50° more westward. The SH polar masses have more equatorward momentum. The African coast has a similar, though lesser effect: SH Atlantic Africa channels air masses equatorward, while the Atlas mountains of NH Africa somewhat shield equatorward motion. In the Indian Ocean and Eastern Pacific Ocean ( through India’s famous monsoon ) the ITCZ wanders back and forth with the seasons.
2. The “Green Sahara” to “Desert Sahara” is described by the relative (im)balance between the hemispheres.
During the last glacial maximum, Northern summers received less summer sunshine and Southern polar air masses were not able to invade as far North, so the ITCZ was constrained and the Sahara was extreme desert.
During the mid-holocene, Northern summers received MORE summer sunshine than present, so SH polar masses were relatively more dense and pushed the ITCZ much farther morthward. This corresponds with the (relative) “Green” Sahara of the mid-holocene.
Present NH summers again experience relatively low amounts of incoming radiance meaning SH polar air masses are not as dense or intrusive to Northern latitudes.
https://1.bp.blogspot.com/-h2NIt1Dvf50/W3u0RqNN4ZI/AAAAAAAAAZA/W5jkliS1KPYiGJ9jZCM6FebPaAOhq39pgCLcBGAs/s1600/sahara%2Btropical.gif
Reblogged this on Climate Collections.
This magisterial new book by Peter Webster gives hope that real climate science is still alive. It should be a reference text for generations to come. Hubert Lamb’s legacy is alive and well. No shrill alarmist politicization, no demonization of the element with the atomic number of the beast. Just solid science rich with curiosity driven inquiry.
And this is the tropics only. A sequel on the high latitudes and poles?
I’m curious about this section:
18.1.6 Why Is the Area of Organized Convection Relatively Constant? 435
Is this about the ITCZ? Does this point to chaos-related self organisation and attractors? Or Lyapunov stability? Does it involve the atmosphere’s IR emission height? Or is that Pandora’s box avoided?
In Hoyos C. D., and Webster, P. J., 2012: (Evolution of the tropical warm pool: Past, present and future. Clim. Dyn. doi: 10.1007/s00382-011-1181-3: available at https://webster.eas.gatech.edu/papers.html) we develop a simple model to determine how a change in SST will effect convective heating and radiative cooling to space. Both are non-linear functions (Claudius-Clapeyron and Stefan Boltzman, respectively). The former dominates convective regions, the latter convectively free regions. Stronger convection occurs where the SST has increased but stronger subsidence surrounds it. Actually, the area of convection decreases slightly when SST increases
The simple results are “validated” with more complex models and allows some simple insights into climate. E.g., during the satellite era, the size of the warm pool (SST > 28°C) has increased by about 20%. Yet areas of convection (as measured by OLR) have not increased. The change in area of >26.5°C (the Bill Gray genesis SST for TCs) has increased even more in area yet the number of TCs and where they form has changed little although there may be a slight increase in intensity. It also makes one perhaps rethink about the hypothesis of an expanding tropics with changes in SST.
If nothing else, I think the results suggest that we should be asking some very basic questions about climate from a fundamental perspective.
PW
Peter Webster
“…I think the results suggest that we should be asking some very basic questions about climate from a fundamental perspective.”
Thank you for this lead. What do you see as the questions that should be addressed? Are these still: regarding anthropogenic CO2, how much impact? Is anthropogenic CO2 the driver of recent climate change?
Is and appreciation for holism, ‘owing to chaos and nonlinearities,’ or or a reasoned fallback position resulting from the realization that the data underlying a supposed rational approach, is all corrupted? A current catch phrase in understanding coronavirus controversies, for example, is that when you mix medicine and politics you get politics. Similarly, when you mix climate science and politics, you get politics.
A co-worker once asked ‘Why is there a Namibian Desert?’
I didn’t know.
It’s not from lack of access to water vapor, since the Namib desert exists in part on coastal lowlands, where it is not blocked by mountains or high terrain.
From paleo records:
There is extreme desert in the Namib today.
There was extreme desert in the Namib at mid Holocene.
And there was extreme desert in the Namib at the Last Glacial Maximum.
Evidently, the Namib has been a desert for perhaps 80 million years!
It would appear that the Namib being a desert is extremely predictable, regardless of global temperature, or any of the numerous climatic changes which have occurred during that time. Why?
Well, 80 million years is ancient in human and climate terms, but less so in geologic terms. Africa, in particular, has very similar size, shape, orientation, and location compared to 50 million years ago. Surface polar air masses encountering the high terrain of the Southern tip of Africa either channel to the west, east, or are cleaved in two. Air masses which move to the west, in full, or in part, impart anti-cyclonic atmospheric motion to the Namib. This motion is also parallel to the coast or flowing off-shore, consistent with the persistent desert. Air masses which are channeled or split to the east, invoke cyclonic and onshore flow, which accounts for the increased precipitation there.
Predictability is not only a function of the number of terms or the tangled inter-dependencies, but on the relative magnitude and bounds of the terms.
The magnitude of the strength of the South African mountains and highlands has dominated atmospheric circulation in this region for 80 million years.
In a similar way, the orbits of the planets are predictable. Interplanetary space is not a complete vacuum – there are still sparse molecules. And there’s a certain amount of friction from these molecules and that means non-linearity. But the gravitational terms dominate the extremely small friction, making prediction, at least on human timescales, predictable.
The atmosphere has some similar predictable outcomes.
Some are fond of pointing out that hemispheric summer and winter are very predictable. Insolation on our solar orbiting spheroid dominates.
Though it fluctuates, we observe jet streams more or less continuously. That earth is a spheroid which creates insolation gradients predicts this since available insolation dominates thermal energy.
We also observe the ITCZ, more or less constantly. But given that earth is an insolated spheroid with denser air masses from each pole converging toward the equator, this is predictable.
As to climate change, what things are predictable?
There are, of course, chaotic fluctuations. But descriptions of the radiative forcing of CO₂ indicate a “mean height of emission to space” of some 6km or so. This is above much of the chaotic fluctuation of the atmosphere of lower levels. It would appear that the radiative forcing from CO₂ would dominate other changes and global warming from CO₂ is predictable.
However, global warming will predictably be dominated by the continuation of greater forces.
Regardless of AGW, there will be extratropical winters and summers.
Regardless of AGW, there will be jet streams in each hemisphere.
Regardless of AGW, these jet streams will fluctuate chaotically.
Regardless of AGW, there will be an ITCZ.
And, of course, regardless of AGW, or even some more significant change, there will be a Namib desert.
What else is dominated by orography, geography, or orbital astronomy?
The link to Hofstadter (1980) doesn’t appear to resolve.
Dear T-E,
Sorry, I don’t quite understand your point,
The reference is:
Hofstadter, D., 1980: An Eternal Golden Braid: Godel,
Escher and Bach. Basic Books, New York, 284 pp.
and a book I thoroughly recommend.
Peter W
Peter Webster: Hofstadter, D., 1980: An Eternal Golden Braid: Godel,
Escher and Bach. Basic Books, New York, 284 pp.
I am not finding that. I am finding Gödel, Escher, Bach: An Eternal Golden Braid, 1999 paperback, 1979 Hardbound.. .
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Ron Clutz. On SST “Why Rely on HadSST3. HadSST3 is distinguished from other SST products because HadCRU (Hadley Climatic Research Unit) does not engage in SST interpolation, i.e. infilling estimated anomalies into grid cells”
Graph from 1995 on shows interesting pulsing of the NH anomalies.
Quite distinct from 2000 on.
Raises the question to me of why a yearly anomaly pulse?
Makes no physical sense.
The only reason for an anomaly that repeats This long and regularly is that the baseline graph somehow is regularly wrong or stuffed up.
Anomalies must go one way or the other on an ad hoc basis.
Perhaps our weather experts could give an opinion on the anomaly of this anomalous anolomy?
““reductionist” and “holistic” perspectives…”
A reductionist approach breaks down because of chaos. Best example is a 10 day weather forecast. It’s based upon the world as a clock you can replicate. It is not clock. It is alive. If it is not alive, it behaves as if it is.
The highest achievement of the world is us. Alive long enough to end up here, arguing about the climate. Playing God as a reductionist doesn’t get you anything close to us. Maybe a slime, but not us.
I am going to say that there are those that keep doubling down on reductionism. If we had 100 times the computing, then this. But it’s the wrong path. The climate will continue to frustrate this approach. No matter how closely the clock is duplicated, it’s not a clock.
The balanced dynamics for the tropics is now well understood. The reduced system for the tropics is nothing more than the shallow water equations with the horizontal divergence forced by the heating/cooling. Browning and Kreiss pointed this out over 40 years ago. And Majda has used that system in conjunction with the usual parameterizations in attempts to better understand the tropical dynamics and physics connections. Clearly the latter depends on the accuracy of the parameterizations which is questionable.
Jerry
Gerald Browning: Browning and Kreiss pointed this out over 40 years ago. And Majda has used that system in conjunction with the usual parameterizations in attempts to better understand the tropical dynamics and physics connections.
Could you list a few of the best references to those works? I’d like to have them to hand as I read through Webster’s book.
Will do tomorrow. There is also a peer reviewed manuscript in press at
Dynamics of Atmospheres and Oceans that introduces the correct reduced
system for the midlatitudes and it is not the primitive (hydrostatic)
equations, I.e., all current climate models are not based on the correct
dynamical system of equations and therefore any conclusions based on those models are not reliable.
Jerry
I found this: The Unique, Well Posed Reduced System for Atmospheric Flows: Robustness In The Presence Of Small Scale Surface Irregularities
For me, it’s behind a paywall.
Matthew,
You can read the final abstract on the site. If Judy wants I can post the manuscript before the review process. The main mathematical arguments are in Section 2 and are unchanged in the final version except for a few additions suggested by one of the reviewers. The main point
Is that there is one and only one system that satisfies the Kreiss Bounded Derivative Theory (BDT) mathematical energy estimates being independent of the high frequencies and that accurately describes the
low frequency motion to the first order of approximation. The manuscript discusses in detail why the hydrostatic system is not that system.
Jerry
Jerry, we look forward to a guest post on your new paper.
Judith:
For what it’s worth, I also finished undergraduate studies (in chemistry) in 1968. I had a professor of astronomy who actually opined that all the major questions in Astrophysics had been addressed at the time.
Your boy Charney is not alone!
Bruce Wells
Matthew,
The reference is (not paywalled):
The role of gravity waves in slowly varying in time troposphere motions near the equator
JAS 2000 57 (24)
4008-4019
Basically for smaller scales of motion in the midlatitudes and all motions in the tropics, the smaller perturbations of the pressure from the mean lead to the dominance of two terms in the potential temperature (entropy) equation.
The necessary balance of those terms means that the vertical component
of velocity (w) is directly proportional to the total of the heating plus cooling (H). Thus one can replace w everywhere in the equations by H.
Then the equations for u, v, and p uncouple. The time dependent term for p is negligible resulting in the horizontal divergence being forced by H.
Jerry
thank you. I got it. searching JAS on your name I also got this:
Multiscale Bounded Derivative Initialization for an Arbitrary Domain
G. L. Browning, H-O. Kreiss
Matthew,
That manuscript shows how the initialization constraints for multiple scales of motion present at the same time can be derived using the Kreiss Bounded Derivative Theory. Those elliptic constraints are the basis for the reduced system in the DAO manuscript. The manuscript also shows how careful one must be in trying to provide appropriate boundary conditions for a limited area model. Global models suppress gravity waves so that those waves are not present in the boundry data. Yet mesoscale storms generate long spatial gravity waves with a short time scale and those waves conflict with the boundary data. If you look at plot of the limited area model, you will see
some noise in the upper left hand corner. That is the gravity aves generated by the mesoscale storm conflicting with the global boundary data. Note that
there was only one storm in the area. When there are more, the gravity waves can add and cause more havoc at the boundaires.
If I added random noise errors to the global boundary data, then all hell would have broken loose unless the magnitude of those errors were less than the truncation error (not likely in practice). Also note that since the vertical velocity w is directly proportional to the heating, any error in the parameterizations is immediately felt in the vertical velocity and thus to the
location, precip and intensity of the storm.
Jerry
Jerry, I am willing to take you word on the shallow water equations but I do question whether they are adequate to create meaningful models of tropical convection. This is a choatic process where turbulence plays a big role. I also doubt that subgrid models can be skillful. Subgrid turbulence models despite tens of thousands of man years invested are still of limited usefulness and don’t work for something like convection anyway. Any thoughts on how to get a handle on things like vertical structure of temperature for example in the tropics?
Perhaps I missed something you mentioned previously though.
Dpy6629,
This is not a subgrid scale model.. it is a balanced model that to first approximation approximates the solution of the equatorial tropospheric
equations of motion when a forcing term is present sufficient to generate a storm. The same balance between w and H occurs in mesoscale solutions in the midlatitudes. See our JAS manuscript on mesoscale storms.
Jerry
Gerald Browning: If you look at plot of the limited area model,
I appreciate your reply, but which manuscript and which figure are you referring to?
Very good paper and doubtless correct in all significant aspects.
However, underlying the entire system is the need for convection to change in order to neutralise radiative imbalances so that an atmosphere can be retained indefinitely.
See recent papers here:
https://www.researchgate.net/project/Dynamic-Atmosphere-Energy-Transport-Climate-Model
Stephen Wilde,
The heating plus cooling includes all forms, e.g., both latent heating and radiative heating. The total of all forcing terms in the potential temperature
equation in the equatorial troposphere.
Jerry
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“Yet extended weather and climate prediction has proven to be universally difficult. For example, even though in Chapter 14 we pointed out that the basic components of ocean–atmosphere interaction are basically understood, each ENSO event (the supposed sum of these parts or components) is very different both in timing, duration, and amplitude. Predictions of whether or not an El Niño or La Niña event will develop following the boreal spring show little skill.”
–
Very few people seem to have noticed the bullet we just missed.
The first 2 months of this year were very warm.
So much so that there was a lot of early speculation that it might become the warmest year ever.
But just as hopes were being raised, May, by some standards was the hottest ever, James Hansen chucked cold water on it.
–
Apparently there may be a La Niña in the offing.
This would act to depress the temperatures enough in the second half of the year to drop it below 2016.
I will just say I hope this one time the prognosticators have got it right.
–
Only one thing can return science back to its truthful foundations.
That requires a drop in global temperatures of reasonable severity for at least 5 years.
I keep looking for that sprig of green that will start the pendulum back.
June might be the month.
It will need a lot more months than this of course.
Matthew,
Figure 12 in our 2002 manuscript.
Jerry
Gerald Browning: Figure 12 in our 2002 manuscript.
Thank you. I see it.
dpy6629,
Read the manuscript. The only balanced solution in the tropics is where the total of the heating plus cooling is directly proportional to the vertical velocity. Actually Charney found a similar conclusion as did Majda.
Jerry
Angech,
Judith is going post my peer reviewed manuscript with my introductory comments soon. The manuscript proves that all climate models are based on the wrong dynamical system of equations. Thus any IPCC conclusions based on those models is unreliable. That leaves proxy data that Stephen Mcintyre has discredited. I am not saying that there is or not global warming.
Just that the the “science” being touted as proving that there is AGW
Is on thin ice.
Jerry
Post is scheduled for Thurs
Thank you Judith. I hope this raises some issues about the IPCC making claims based on climate models.
Jerry
Matthew,
The interesting question is whether these mesoscale gravity waves can initiate new storms. As there are no observational systems that can separate out these waves before the storm generates them, this would mean that no numerical model can generate the correct mesoscale solution.
Jerry