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At the Assembly: Wednesday highlights

At the Assembly: Wednesday highlights

We’re halfway through the General Assembly already! Once again there is lots on offer at EGU 2015 and this is just a taster – be sure to complement this information with EGU Today, the daily newsletter of the General Assembly, available both in paper and for download here.

Today features more Union-wide events which celebrate the conference theme: A Voyage through Scales. First up is a symposium on the geocomplexity of scales (US1): a series of talks which will explore the variability of geosystems over a huge range of scales both in space and time. This is followed by a Lecture of general scientific interest (GL2) in the afternoon on archives of the continental crust by Chris Hawkesworth, which you can join in Y1 from 13:30 onwards. You can follow the sessions on Twitter with #EGU15US and #EGU15GL, and, if you’re not attending, tune in with the conference live stream.

The educational and outreach symposia (EOS) feature sessions on geoscience education, science communication, public engagement and related topics. This year there are a large number of EOS sessions on offer: today you could head over to the geoethics for society: general aspects and case studies in geosciences session, from 13:30–17:00 in Room R12, where talks will focus on the ethical and social implications in geoscience. Make sure to check the EOS programme to see if anything else catches your fancy.

Another promising event set for today is the EGU Award Ceremony, where the achievements of many outstanding scientists will be recognised in an excellent evening event from 17:30–19:00 in Room Y1. Here are some of the lectures being given by these award-winning scientists:

Today also sees the Penck Lecture of the Geomorphology Division take place. Ann V. Rowan will be talking about what can mountain glaciers tell us about climate change: quantifying past and future discharge variations in the Southern Alps and Himalaya (KL2) from 12:15–13:15 in G2.

Now on to short courses! Today offers the opportunity to learn how to write the perfect paper in geomorphology (SC47/GM11.2, 17:30–19:00 in G2), learn the basics of climate modelling (SC43, 19:00–20:00 in B12) and increase your chances of securing funding for your next project by attending this two part workshop: How to write a successful ERC Starting Grant proposal (SC19/TS10.1, 15:30–17:00 / Room B4), followed by the broader, finding funding: how to apply for a research grant (SC39, 17:30–19:00 / Room B13).

And check out some of today’s stimulating scientific sessions:

Finally, remember to take the opportunity to meet your division’s representatives in the day’s Meet EGU sessions and, if you’ve had enough of the formalities, head on over to GeoCinema, where you’ll find some great Earth science films, including the finalists of EGU’s Communicate Your Science Video Competition. Make sure to vote on your favourite entries by ‘liking’ the videos on the EGU YouTube channel.

Have an excellent day!

Geocomplexity and scales: new worlds or scaling?

To celebrate this year’s General Assembly theme – A voyage through scales – Shaun Lovejoy, President of the Nonlinear Processes in Geosciences Division (NP), takes us on a tour of how scaling might change our view in a range of Earth science topics: from clouds through to geological surfaces.

When van Leeuwenhoek peered through the first microscope, he was amazed at the new worlds lurking in a drop of water. That was the 17th century and today’s atom-imaging microscopes are developed precisely because of the promise of such discoveries. This contemporary scale-by-scale “newness” idea was graphically illustrated by K. Boeke’s “Cosmic View” (1957) which starts with a photograph of a girl holding a cat, first zooming away showing the surrounding vastness of space, and then zooming in until reaching the nucleus of an atom. Even better known is the derivative TV series and book by P. Morrison (“Powers of ten”, 1983), which encouraged the idea that nearly every power of ten in scale hosted different phenomena. This “new worlds” paradigm could also be termed “scalebound”; it is a severe constraint on one’s conceptual horizons [Mandelbrot, 1981]. From here, it is a short step to the “phenomenological fallacy”: the confounding of form and mechanism which we discuss below [Lovejoy and Schertzer, 2007].

Schematic diagram showing a typical phenomenologist’s view of meteorology (reproduced from [Atkinson, 1981] who adapted it from [Orlanski, 1975],).  The straight line, added in [Schertzer et al., 1997], is the Kolmogorov scaling ≈-1/3 l2/3 where the interpretation has been made that the lower right corner of the inner frame is 2 m and 10 s, whereas the upper left intersection of the inner frame with the extension of the line corresponds to one month.  This corresponds to a turbulent energy flux  ≈ 4x10-3 W/Kg which is a close to the global average ≈ 10-3 W/Kg estimated in [Lovejoy and Schertzer, 2013].  Note that the beginning of the transition from “synoptic” to “climatological scales” corresponds to planetary spatial scales, as required in order to explain the weather/ macroweather transition.

Fig 1. Schematic diagram showing a typical phenomenologist’s view of meteorology (reproduced from [Atkinson, 1981] who adapted it from [Orlanski, 1975],). The straight line, added in [Schertzer et al., 1997], is the Kolmogorov scaling where the interpretation has been made that the lower right corner of the inner frame is 2 m and 10 s, whereas the upper left intersection of the inner frame with the extension of the line corresponds to one month. See  Lovejoy and Schertzer, 201 for further details. Note that the beginning of the transition from “synoptic” to “climatological scales” corresponds to planetary spatial scales, as required in order to explain the weather/ macroweather transition.

“New worlds” thinking is now so entrenched that we find it obvious that “zooming in” opens up hidden secrets. Most of us would probably express more wonder if we zoomed in only to find that nothing had changed, if the process was scale invariant! Yet in the last thirty years anti-scaling prejudices have started to unravel; at first largely thanks to Mandelbrot’s path breaking “Fractal Geometry of Nature” (1983). His avant-garde use of computer graphics to render scaling fractals visually showed the realism of scaling.

These early scaling models were novel and striking, but they suffered from two limitations that ultimately made them unrealistic: they were simultaneously “monofractal” and “self-similar”. The first implies that strong and weak phenomena have the same morphologies whereas the second implies that the rule that allows us to zoom from large to small is the same in all directions (isotropic): the small and large are statistically carbon copies. But clouds have notoriously complex anisotropies and even casual inspection discloses that they tend to become flatter at larger scales, while being more wispy, filamentary at smaller scales (see the figures below). Indeed, by the 1980’s meteorologists had formalized the idea that atmospheric phenomena were qualitatively different over each factor of 10 in scale. The far right column in fig. 1 lists the scale ranges in Orlanski’s influential classification and fig. 2 shows a more recent example; such “space-time” or “Stommel” diagrams have adorned meteorology textbooks for decades. For the topography, geomorphologists had similarly catalogued complex anisotropic terrain structures and textures that also changed with scale.

A Stommel diagram showing the length and time scales associated with typical atmospheric and oceanic dynamics, adapted from [Steele, 1995] (fig. 8.9b of [Lovejoy and Schertzer, 2013])

Fig 2. A Stommel diagram showing the length and time scales associated with typical atmospheric and oceanic dynamics, adapted from [Steele, 1995]. You can read more about the diagram in Lovejoy and Schertzer, 2013.

The idea of self-similar geosystems provoked widespread disbelief. Indeed, throughout the 1980’s the main appeal of scaling in geosystems was the implicit simplicity of the (supposedly unique) fractal dimension. However, by the 1990’s, the limitations of monofractal, self-similar geomodels started to become quantitatively apparent and interest in scaling started to wane (e.g. [Klinkenberg and Goodchild, 1992]; the collection [De Cola and Lam, 1993], [Quattrochi and Goodchild, 1997] were the last of the genre).

Ultimately, it fell upon the shoulders of a few die-hards to seize on the kernel of scaling wisdom – that unique dynamical mechanisms could yield structures spanning wide ranges of scale – to build more realistic models. By the time the key anisotropic and multifractal generalizations of scaling had been developed, activity was concentrated in the newly formed Nonlinear divisions of the European Geophysical Society (1989) and the American Geophysical Union (1997).

zooming must be made anisotropic – so that for example changing from one scale to another involves not only enlarging/shrinking but also rotations and squashing of structures.

zooming must be made anisotropic – so that for example changing from one scale to another involves not only enlarging/shrinking but also rotations and squashing of structures.

The key to producing realistic wide scale range models – to overcoming the phenomenological fallacy – turned out to be to generalize the notion of scale and scale changes, to go beyond isotropic zooms and self-similarity (additionally, multifractals are needed to overcome the limitations of monofractals, but that’s another story). The zooming must be made anisotropic – so that for example changing from one scale to another involves not only enlarging/shrinking but also rotations and squashing of structures (see e.g. fig. 3). In itself this is not enough; it must be done in such a way that the system has no characteristic length scale; the rule going from one scale to another must only depend on the ratios of the two scales; mathematically it defines a group and its generator (“Generalized Scale Invariance” (GSI), [Schertzer and Lovejoy, 1985]; and ch. 7 in [Lovejoy and Schertzer, 2013]). In this case, the small and large scale morphologies can be different, yet can nevertheless be products of unique mechanisms acting over wide ranges of scale. In the absence of symmetry breaking mechanisms, the symmetries are respected so that by formulating the problem in terms of scale symmetries, GSI explains why so many real world systems are scaling. Fig. 4 shows an example with a fairly simple anisotropic mechanism involving only squashing in a fixed direction with scale, and fig. 4b zooms into multifractal clouds with both scale by scale rotation and squashing. . These examples graphically demonstrate how wrong “new world” intuitions can be.

Top: a multifractal simulation of an anisotropic geological surface with the proverbial lens cap included to indicate the scale.  One could easily image developing a phenomenological model to explain the left-right ridges.  Bottom:  The same simulation but blown up 64 times; at this scale a rather different model might be invoked even though a unique mechanism is responsible for the whole scale range (top and bottom).  Reproduced from [Lovejoy and Schertzer, 2007] (fig. 1.13 in [Lovejoy and Schertzer, 2013]).

Fig 4.a) Multifractal simulation of an anisotropic geological surface with the proverbial lens cap included to indicate the scale. One could easily image developing a phenomenological model to explain the left-right ridges. Bottom: The same simulation but blown up 64 times; at this scale a rather different model might be invoked even though a unique mechanism is responsible for the whole scale range (top and bottom). Reproduced from [Lovejoy and Schertzer, 2007] (fig. 1.13 in [Lovejoy and Schertzer, 2013]).

Top: a multifractal simulation of an anisotropic geological surface with the proverbial lens cap included to indicate the scale.  One could easily image developing a phenomenological model to explain the left-right ridges.  Bottom:  The same simulation but blown up 64 times; at this scale a rather different model might be invoked even though a unique mechanism is responsible for the whole scale range (top and bottom).  Reproduced from [Lovejoy and Schertzer, 2007] (fig. 1.13 in [Lovejoy and Schertzer, 2013]).

Fig 4.b) Zooming into multifractal clouds with both scale by scale rotation and squashing.

 

 

 

 

 

 

 

 

 

 

 

 

 

But can GSI really explain the meteorologists’ phenomenology (fig. 1, 2)?   Evidence that it can is surprisingly close to hand: what was not noticed is that space-time diagrams are almost invariably linear on log-log plots (the alignment along the diagonal in fig. 1), so that space-time relationships are power laws, they don’t have characteristic scales. But it gets better: on dimensional grounds, if the (solar induced) energy flux dominates the horizontal dynamics, the value of the energy flux theoretically calculated from the solar forcing gives the correct intercept. Finally, due to multifractality, the space-time relation is itself statistically variable: this can be easily taken into account (fig. 2); adding realism and credence to the scale-free explanation. Finally, the weather – macroweather transition scale (corresponding to the typical lifetimes of planetary scale structures, about 10 days), is also well reproduced.

By Shaun Lovejoy, Nonlinear Processes in Geosciences Division President

References

Atkinson, B. W. (1981), Mesoscale Atmospheric Circulations, Academic Press, London.

De Cola, L., and N. Lam (Eds.) (1993), Fractals in geography, Prentice-Hall, Englewood, N.J.

Klinkenberg, B., and M. F. Goodchild (1992), The fractal properties of topography: A comparison of methods, Earth surface Proc. and Landforms, 17, 217-234.

Lovejoy, S., and D. Schertzer (2007), Scale, scaling and multifractals in geophysics: twenty years on, in Nonlinear dynamics in geophysics, edited by J. E. A.A. Tsonis, Elsevier.

Lovejoy, S., and D. Schertzer (2013), The Weather and Climate: Emergent Laws and Multifractal Cascades, 496 pp., Cambridge University Press, Cambridge.

Mandelbrot, B. (1981), Scalebound or scaling shapes: a useful distinction in the visual arts and in the natural sciences, Leonardo, 14, 43-47.

Orlanski, I. (1975), A rational subdivision of scales for atmospheric processes, Bull. Amer. Met. Soc., 56, 527-530.

Quattrochi, D., and M. Goodchild (Eds.) (1997), Scaling in Remote Sensing and Geographical Information Systems, Lewis, Boca Raton, Florida.

Schertzer, D., and S. Lovejoy (1985), Generalised scale invariance in turbulent phenomena, Physico-Chemical Hydrodynamics Journal, 6, 623-635.

Schertzer, D., S. Lovejoy, F. Schmitt, Y. Chigirinskaya, and D. Marsan (1997), Multifractal cascade dynamics and turbulent intermittency, Fractals, 5, 427-471.

Steele, J. H. (1995), Can Ecological concepts span the land and ocean domains?, in Ecological time series, edited by J. H. S. T. M. Powell, Chapman and Hall, New York.

GIFT at the Assembly: Mineral Resources

GIFT at the Assembly: Mineral Resources

The EGU’s Geosciences Information for Teachers (GIFT) programme offers teachers attending the conference the opportunity to hone their Earth science skills. The General Assembly workshop is one of GIFT’s most important activities of the year, combining talks on current research with hands-on activities presented by educators. What’s more, scientists can also come to the sessions – here’s what’s in store…

The theme of this year’s GIFT workshop (EOS1) is Mineral Resources – the event will explore one of the most important challenges faced by modern society: access to raw materials, including base and strategic minerals, in a rapidly developing and growing world. Featuring talks by leading scientists in the field, the workshop will kick off with a discussion on raw materials and their sustainability in the 21st century (at 8:45 in Room G10). This is followed by two great talks on where do minerals come from and how they get there, by Laurence Robb of the University of Oxford, after which you can learn about the role of inorganic chemistry in the formation of ore deposits at the hands of Kliti Grice from Curtin University, Australia. This is just a taster, though – you can find out more about the workshop here.

Where is the EGU General Assembly?

The General Assembly is almost here. Presentations are (hopefully!) complete, posters are printed, bags are packed and all you need to do is get to the conference…

The Austria Center Vienna (ACV), the Assembly venue, is not far from the city centre and can easily be reached from the airport and central train station. You can get there via the U1, the red line in the underground map below:

The ACV is located next to the Kaisermühlen/Vienna Int. Centre metro station (click for larger).

The ACV is located next to the Kaisermühlen/Vienna Int. Centre metro station (click for larger).

The ACV is located next to the Kaisermühlen/Vienna Int. Centre (VIC) U-Bahn station (take the U1 towards Leopoldau if you’re coming from the city centre). Wiener Linien, Vienna’s public transport agency, provides a journey planner on their website, including information about getting to the city centre from the airport by train.

regular bus service connects the airport with the conference centre too. Bus 1183 stops just outside the ACV (Wien Kaisermühlen VIC – Wagramer Straße). Further travel information – including about where to find taxis at the airport – can also be found on the airport’s website.

Once you’re in, you can navigate your way to your first session of the day using these maps of the Austria Center!

The ground floor of the Austria Center Vienna.

The ground floor of the Austria Center Vienna.

 

The EGU General Assembly is taking place in Vienna, Austria from 12 to 17 April. Check out the full session programme on the General Assembly website. 

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